Menno en Erwin over de natuur en wetenschap: Newsletter ENG

Newsletter #199 Fossils: Top Fossil Hunting Sites in the Netherlands

Erwin Balkema — Sun, 14 Dec 2025 20:24:19 GMT

Fossils: Top Fossil Hunting Sites in the Netherlands

Perhaps you think that finding fossils is something for far-off lands: a Tyrannosaurus in Colorado. But closer to home, on the Jurassic Coast of Southern England, Mary Anning found a skeleton of an ichthyosaur – a long-extinct marine reptile – back in 1811, when she was just 12 years old.

Astonishing was the find made as a young boy on a sunken lane near Epen in Limburg: a large piece of coal with the unmistakable imprint of a large plant. It had to be old. Not realizing how old it actually was. It dates from the Carboniferous period, 300 million years ago. A find right near the Heimans quarry, which has since been declared a geological monument. There, coal layers come to the surface that once originated in a place where Suriname lies today.

Yes, there are quite a few special fossil sites in the Netherlands, petrifications of plants and animals or their imprints. Together with fossil expert Harry Huisman, we review the top five locations at the Hunebedcentrum in Borger. For this, we travel throughout the country, going further and further back in time.

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1. The Maasvlakte

We begin at the Maasvlakte near Rotterdam. There, you can simply stumble upon bones and molars of mammoths. These can be 40,000 years old or older. These finds date from the time when there was a direct land connection to England in what is also called Doggerland. Around 8,000 years ago, this came to an end and the land was submerged.

Due to climate change, the mammoths here had already been driven away; until 4,000 years ago they still lived on the Siberian island of Wrangel. The current finds from the North Sea – and everywhere sand is dredged onto the North Sea beaches – are not fossils in the strict sense. Harry Huisman explains that these are still real, non-petrified bones, tusks, and molars; therefore, they are given the name sub-fossils. This also applies to the horn of a Soay sheep which, fished up above the Dogger Bank, points to early livestock farmers, certainly ten thousand years ago.

2. Cadzand and Walcheren

Finds of real fossil shark teeth on the beach of Cadzand in Zeeuws-Vlaanderen and on that of Walcheren date from much earlier. The teeth, over 7 cm long, found in Cadzand (and on Belgian beaches) likely come from the four (or even ten) meter long broad-toothed white shark.

Apart from the mineralized teeth, nothing remains of these enormous cartilaginous fish that swam around 20 million years ago. Shark teeth found on the De Kaloot beach near Vlissingen are another thirty million years older, together with fossil shells from the same era.

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3. Sint Pietersberg

In the marl quarries of the Sint Pietersberg in Maastricht, skull parts of a fearsome sea lizard, the Mosasaurus (now in Teylers Museum in Haarlem), were found in 1766. About seventy million years ago, these animals, up to 18 meters long, made the seas unsafe.

Twelve years later, in 1774, a virtually complete skull was recovered under the leadership of Hoffmann, including the enormous rows of teeth. This was stolen on Napoleon’s orders in 1794 and this world-famous specimen of Mosasaurus hoffmanni still lies in the Museum of Natural History in Paris. Scandalous, according to Harry Huisman.

Fortunately for Maastricht, a complete, 12-meter-long related sea lizard was found again in the Pietersberg in 1998. The people of Maastricht call the animal Bèr, but the scientific name is a bit longer: Prognathodon saturator.

4. Winterswijk

During the greatest extinction event we know of, 252 million years ago, 96 percent of all living animals on earth lost their lives. Cause: volcanic eruptions in Siberia. Those who profited from this can be found in a not-so-large stone quarry near Winterswijk. Here is a site of Muschelkalk, shell limestone that is used in agriculture as dolomite lime.

And in these layers, which begin only one and a half meters below the surface, we find fossil skeletal parts of 240-million-year-old plesiosaurs. By now, two species of the genus Nothosaurus have been found here, water predators up to a maximum of one meter in length. Who knows what else is to be found. Recently, in addition to a very old woodlouse, an unknown fish species was also found.

There is a monthly excursion in the quarry in Winterswijk where one can also search, but, Harry Huisman warns, one must register for this.

5. Northern Netherlands

A bit further north, it is a real fossil feast. That is the richest fossil site in Europe, if one is to believe Harry. And we do, because as he explains, the Northern Netherlands is the European geological sinkhole.

Rivers like the Rhine, the Meuse, the Scheldt, the Elbe, and the Weser only ever flowed into this area. And above all, so did the Eridanos, the gigantic river of 2,700 kilometers in length that flowed from Northern Scandinavia into the Northern Netherlands from forty to one million years ago. It roughly followed the current Baltic Sea. All these currents dragged large quantities of erratic boulders and old fossils to this region.

Therefore, it is not surprising that we can find fossils from many corners of the world here, and it should come as no surprise that this includes, for example, fossil corals that are 440 million years old. Many of these fossils can be found in the Hondsrug. Harry Huisman describes them in a book that will be released soon. But in a future podcast, we will also pay attention to such fossils, which we might just encounter along the way. They must have come to the surface, for example, when roadworks were done, or farmers cultivated their lands.

🎙️ Listen to the full Dutch episode on mennoenerwin.nl — your monthly guide to nature, science, and wonder.

We now have three publications:

Dutch podcast on wednesday
Nieuwsbrief NL → dutch newsletter
Newsletter ENG → same newsletter but in english

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Newsletter #198 ❄️ December — The Dark Month, Full of Life

Erwin Balkema — Sun, 07 Dec 2025 15:01:04 GMT

❄️ December — The Dark Month, Full of Life

🌘 A Month of Contrasts

December sits around the shortest day of the year, with the lowest number of sunshine hours. Even though solar radiation has increased in all months due to cleaner air and more high-pressure zones, December still feels like stepping into a dimly lit room.

But nature compensates.

We celebrate Christmas, the days start lengthening again, and—depending on November—there may still be mushrooms everywhere. Over 200 species are recorded in December, though that number will halve next month.

A few brave plants keep blooming too: a surprising white dead-nettle here, a lone dandelion there, and of course the indefatigable daisy, flowering the whole year round.

🌿 Plants in December

Besides the year-round bloomers, some species are at their seasonal limit—like yarrow and shepherd’s purse.

The forest looks bare, but a few species keep their leaves:

ivy
some ferns
brambles

And then there’s holly—the only tree still strikingly green. A female holly even carries bright red berries, our classic Christmas symbol of resilience and hope. In open spaces, holly can grow up to ten meters and reach 300 years of age.

Its tough, leathery, spiny leaves are iconic. A fun scientific mystery: older holly leaves lose their sharp teeth and become more rounded. Nobody knows exactly why.

Another evergreen of December is the mistletoe, a half-parasite living high in trees in southern Netherlands. Its berries are poisonous to humans, but birds spread the seeds by wiping their sticky beaks against branches—nature’s own glue trap.

Mistletoe is ancient folklore:

💚 symbol of peace

💚 protector against lightning

💚 sealing marriages

💚 and yes… still a license to kiss beneath it 😉

🍄 Mushrooms, Birds & Wildlife in December

December can be an excellent mushroom month—depending on the weather. Some species disappear quickly (birch boletes, chestnut boletes, yellow earthballs), but over 100 species still thrive this month.

Mushrooms on dead wood continue well into January:

elf cups
turkey tails
crust fungi
jelly fungi
tough tinder fungus

Birds fight through the cold. Hard frost (rare lately!) is tough on kingfishers and green woodpeckers.

Insects? Almost none above ground—but beneath the soil lies a bustling world. As Jac. P. Thijsse said: “There must be life down there, otherwise wrens and robins wouldn’t be so busy digging.”

Small mammals stay hidden.

Hedgehogs hibernate, squirrels stay close to their food stores, and hares and rabbits rely more on twigs and roots in December. After steep declines (up to 75%), both populations are slowly stabilizing.

Large mammals? Thriving.

Encounters with roe deer and wild boar are more common than ever—sometimes too common. Roe deer now number over 220,000 in the Netherlands. Wild boar officially belong only on the Veluwe and in North-Limburg, but they wander freely. Their population doubled from 4,800 in 2019 to over 10,000 in 2025, and road accidents are daily occurrences.

🔎 December Tips for Your Walks

🌼 Look for winter bloomers — far more species flower than you’d expect.
🍄 Hunt mushrooms on dead wood — discover jelly and tinder fungi.
🌳 Spot holly trees — berry-bearing trees show you the male/female ratio.
🦢 Enjoy the goose season — greylag, brent, barnacle, bean, and Canada geese.
🐦 Observe garden battles — who wins: the blue tit or the great tit?

🎙️ Listen to the full Dutch episode on mennoenerwin.nl — your monthly guide to nature, science, and wonder.

We now have three publications:

Dutch podcast on wednesday
Nieuwsbrief NL → dutch newsletter
Newsletter ENG → same newsletter but in english

You can change what you will receive in your substack email from us in the bottom manage subscription or go to the link https://menno-en-erwin.substack.com/manage-subscription

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je kan je subscripties wijzigen zodat je alleen de engelse of nederlandse newsbrief ontvangt hier https://menno-en-erwin.substack.com/manage-subscription

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Newsletter #197 It’s Green and It Eats Ants. A Woodpecker?

Erwin Balkema — Sun, 30 Nov 2025 12:35:53 GMT

It’s Green and It Eats Ants. A Woodpecker?

The European Green Woodpecker rarely drums, but it laughs loudly.

Its unmistakable call usually gives it away long before you see it. About 30 cm long, these medium-sized birds move nimbly across trunks, climbing effortlessly, and flying in a rolling pattern: a few wingbeats followed by a short glide to the next tree — or straight down to the ground.

Because that’s where they hunt.

For ants.

Unlike other woodpeckers, the Green Woodpecker has a relatively weak bill, not suited for chiseling deep into wood. Instead, it comes equipped with a remarkable weapon: a 10 cm long sticky tongue covered with barbed hooks, perfect for catching ants and larvae in grasslands.

You can recognise them easily: a beautiful green back, a bright red crown, and a black mask around the eye. Males also have a red “moustache stripe” under the eye — females have a black one. Their grey, dagger-like bill is strong enough to dig into soil and anthills, but unfortunately not strong enough to carve out a proper nest cavity. That’s why Green Woodpeckers must rely on abandoned nest holes from other woodpecker species — or hope to stumble upon a nicely decaying tree they can work their way into.

This might raise the question: is the Green Woodpecker really a woodpecker at all?

Yes — absolutely.

They are true tree-climbers, equipped with the classic woodpecker foot design: two toes pointing forward and two pointing backward. Combined with stiff tail feathers, this gives them incredible grip on bark. But when it comes to getting food, it’s all about that long, barbed, sticky tongue.

The population has been slowly increasing again in recent years, now reaching about 11,000 breeding pairs in the Netherlands. As a resident species, we can enjoy them year-round.

Less enjoyable, perhaps, for the ants.

How to Tell Our Woodpeckers Apart

1) Great Spotted Woodpecker

Our most common woodpecker. Smaller than the Green Woodpecker (around 25 cm). Black-and-white plumage, red underbelly, and males have a red spot on the nape. Famous drummers and tireless chiselers.

2) Middle Spotted Woodpecker

A bit smaller. Both sexes show a red patch on the crown. Weak drummers, usually found high in the trees. Around 2,000 breeding pairs, mostly in eastern Netherlands.

3) Lesser Spotted Woodpecker

Even smaller (15 cm). Males have a red crown, but otherwise this species is entirely black-and-white. Behaviour similar to the Great Spotted Woodpecker. Population is roughly half the size of the Green Woodpecker.

4) Black Woodpecker

The largest woodpecker in our country (about 50 cm). Entirely black with a bold red cap. Loud drumming, striking calls. Around 1,500 breeding pairs, mainly in wooded areas such as the Veluwe.

5) Wryneck

A small (16 cm) brownish woodpecker species. Winters in Africa. About 200 breeding pairs in the Netherlands, mostly in Friesland and the Veluwe.

Finally, the Grey-headed Woodpecker, which resembles the Green Woodpecker but is slightly smaller and greyer, is only seen here as a rare vagrant.

🎙️ Listen to the full Dutch episode on mennoenerwin.nl — your monthly guide to nature, science, and wonder.

We now have three publications:

Dutch podcast on wednesday
Nieuwsbrief NL → dutch newsletter
Newsletter ENG → same newsletter but in english

You can change what you will receive in your substack email from us in the bottom manage subscription or go to the link https://menno-en-erwin.substack.com/manage-subscription

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Newsletter #196 Our brains are capable of mind-boggling feats, yet we still know very little about how they pull it off

Erwin Balkema — Tue, 25 Nov 2025 20:24:44 GMT

Our brains are capable of mind-boggling feats, yet we still know very little about how they pull it off

At least 86 billion nerve cells are active in our brains. They form approximately 500 billion connections with each other. And perhaps there are many, many more.

We know a little about how nerve cells process and store information. First in short-term memory, and then in long-term storage, which, under certain circumstances, we can still consult decades later. We have learned a great deal from the learning behavior of a sea slug, Aplysia (the sea hare), which has only 20,000 neurons. This hefty, algae-eating slug exhibits complex behavior, avoids touch and pain, and can defend itself against enemies with clouds of purple ink.

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We understand how their nerve cells transmit information thanks to the work of neurobiologist Eric Kandel. In 2000, he received the Nobel Prize in Physiology or Medicine for his contribution to our knowledge of learning and memory. This was due to his crucial decision to abandon his work on memory storage in rats in New York—animals with nearly 200 million neurons—to work on such a “primitive” animal in France instead

In his nearly 1,000-page textbook, “Principles of Neural Science” (co-authored with James Schwartz), Kandel described what he considered the five essential questions about how our brains work: How do adult brains develop? How do brain cells talk to each other? How do connections between nerve cells influence our behavior and perception? How, in turn, do our experiences influence the connections between nerve cells and different brain areas? And how do diseased brains differ from healthy ones?

Research has found answers to many of these questions. But always in small parts, and many major questions remain unanswered.

Thanks to new techniques, we know that localization—the specific place in the brain—is important for much of what happens in our heads. But simultaneously, we have increasingly discovered that the contacts between brain cells and brain regions are essential. This often happens in rapid networks where information is circulated. We owe such insights to new technologies, such as three-dimensional X-rays in a computed tomography (CT) scanner. We can track our metabolism through positron emission tomography (PET), where a radioactive substance is injected for an activity scan. Magnetic resonance imaging (MRI) uses a magnetic field and radio waves to track the presence of chemical elements like hydrogen, carbon, nitrogen, and phosphorus in our brains. When this is measured during specific brain activities, it is called functional MRI (fMRI). And finally, we can track electrical activity in brain regions with increasing precision using electroencephalography (EEG) measurements.

Small electrical currents in the membranes of our nerve cells, called action potentials, play a major role in communication between brain cells. This is often combined with the release of chemical messengers, known as neurotransmitters, into the synaptic cleft between cells. Information exchange between nerve cells occurs in other ways too, such as via direct small gap-junctions, and the role of glia (support cells) is gaining increasing attention. The timing of brain activity also matters. Simultaneous activity of nerve cells strengthens the connection between those cells—a form of learning reflected in anatomy. Brains turn out to be much more flexible and changeable than we previously thought.

We gain new insights into the working of our brains almost daily. It is becoming increasingly difficult to oversee the entire field of neuroscience. Of the 114 Nobel Prizes in Physiology or Medicine, 30 have gone to neurosciences.

Within chronobiology, the influence of light on emotional centers and the distinct clock functions of our brains have recently played a role. Therapeutically, the ability to intervene with electrical currents in conditions like Parkinson’s tremors has recently been expanded to treat tinnitus (ringing in the ears), to name just a few examples.

It is becoming increasingly clear that we can learn a lot from the other animals on Earth. In many functions, they are far better than us, sometimes with much smaller brains than ours (compare the sea slug). A phenomenon once considered mysterious and unique to humans, such as (self-)consciousness, appears to be distinctly present in many animals.

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Many great questions remain open, such as how exactly our experiences are stored, how logical reasoning is structured, the influence of our perception of the environment, and the role of sleep. regarding diseases, we struggle with the increasing problem of Alzheimer’s and Parkinson’s, despite all the research. It is beautiful, yet barely understood, how much recovery and adaptive capacity lies hidden in our healthy brains. Anyone who thinks they must fall back on a “collective, external consciousness” (for which convincing proof has yet to be provided) to understand our brains is unfairly underestimating their own minds.

Tips to keep a brain healthy:

Ensure sufficient sleep and good sleeping conditions.
Stay mentally active: learn an extra language, read, or learn to play a new musical instrument.
Stay physically active: participate in sports, or in any case, ensure sufficient movement.
Eat a healthy and varied diet; avoid fast food and the pre-fabricated products super-markets are full of.
Continue to be amazed by what is happening around you; actively capture light, images, sounds, smells, and touches, and enjoy what pleases you.

🎙️ Listen to the full Dutch episode on mennoenerwin.nl — your monthly guide to nature, science, and wonder.

We now have three publications:

Dutch podcast on wednesday
Nieuwsbrief NL → dutch newsletter
Newsletter ENG → same newsletter but in english

You can change what you will receive in your substack email from us in the bottom manage subscription or go to the link https://menno-en-erwin.substack.com/manage-subscription

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je kan je subscripties wijzigen zodat je alleen de engelse of nederlandse newsbrief ontvangt hier https://menno-en-erwin.substack.com/manage-subscription

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Newsletter #195🔬 Fraud in Science

Erwin Balkema — Mon, 17 Nov 2025 08:34:58 GMT

🔬 Fraud in Science

When “science as human work” shows its human flaws

In his sober 1978 book on the scientific enterprise, Professor Arie Rip gave it the fitting title “Science as Human Work.” And indeed — scientists are ordinary people. Their profession is unusual and demanding, and ideally they possess a strong sense of self-criticism. Yet they are not immune to human weaknesses: career anxiety, jealousy, greed, arrogance, convenience. All of it lurks beneath the surface.

Looking back, it is striking that Arie Rip barely addressed fraud in his book — because scientific misconduct certainly occurs. Sometimes dramatically, as in two major Dutch scandals, and increasingly also on a smaller scale. The pressure to survive in academia today is enormous: researchers must publish prolifically (and preferably in top journals), secure funding, and build influential networks. Permanent positions and promotions are scarce, and competition is fierce. Add to that the commercial pressure of fake journals and conferences, and the system becomes even more vulnerable.

Ultimately, it is the critical mindset within science — the commitment to integrity and mutual scrutiny — that keeps the field afloat.

📺 The Buck Affair (1990)

In April 1990, the Dutch 8 o’clock news opened with a sensational claim: two Dutch researchers expected to cure the until-then deadly disease AIDS within a year. Professor Buck (Eindhoven) and his Amsterdam colleague Goudzwaard presented a method to inhibit AIDS through changes in genetic code. Buck briefly became a national hero.

But shortly after, their article in Science had to be retracted. Colleagues demonstrated that the reported results could not be correct. Their conclusion: too few control experiments.

And so began the Buck Affair, ending abruptly in disappointment rather than triumph.

📉 The Stapel Scandal

Internationally, the Netherlands became infamous through the case of celebrated social psychologist Diederik Stapel. Suspicion began with his own students. Investigations by the universities of Amsterdam, Groningen, and Tilburg ultimately revealed that Stapel had fabricated research data himself. He reported extensive results — including studies in schools he had never visited — and personally filled in entire datasets.

More than half of his publications (55 articles and 24 book chapters) turned out to be fabricated and had to be withdrawn. PhD theses based on his data were invalid. Fraudulent grants totaled more than €1.4 million. In 2011, Stapel returned his doctoral title. His legal punishment amounted to 120 hours of community service — a sentence that foreign newspapers followed with disbelief. The New York Times called him “the biggest con man in science.”

🧭 “A little integrity is impossible” — Ien Dales

If anywhere this statement holds true, it is in science. The Stapel case was extreme in scale and severity, but even small deviations from integrity — massaging data, omitting inconvenient results — are problematic. The list is long:

Passing off others’ work as your own (plagiarism)
Excluding rightful contributors from the author list
Or the opposite: unjustified co-authorship
Misusing statistical analyses
Carelessness in research or reporting
Allowing misconduct by colleagues

The Stapel scandal made painfully clear that existing safeguards were insufficient. Peer review did not catch it, nor did dissertation committees or supervisory structures.

Journalist Frank van Kolfschooten, who investigated many cases of scientific fraud, described what has since changed in academia — largely thanks to the public impact of his work:

A second supervisor is now mandatory for PhD projects
Dissertation committees must meet stricter independence criteria
National and institutional codes of scientific integrity have been established
Every university now has an integrity committee
The LOWI (National Body for Scientific Integrity) serves as appeals board
Strict requirements exist for data storage and accessibility
Every new PhD graduate publicly commits to the Dutch Code of Conduct for Scientific Practice

Is that enough?

Science remains human work — but thankfully, it is carried out by highly critical people who understand what is at stake. The strongest safeguard is that every scientific result must withstand repetition. As the Romans already knew:

Repetition is the mother of science.

📝 Five Tips for Navigating Scientific Integrity

1) Examine the quality of the scientific information you encounter.

Journalists (and certainly politicians) seldom provide sources. Wikipedia offers no guarantees, but many articles list references — a useful place to start.

2) Scientific journals must now explain their review procedures.

Authors of scientific articles can always be contacted directly.

3) If you have legitimate concerns about research, you can contact the integrity committee of the institution involved.

4) Appeals can be directed to the LOWI (National Body for Scientific Integrity).

5) For an excellent overview of the Dutch situation, read Frank van Kolfschooten’s books:

Valse Vooruitgang and Ontspoorde Wetenschap.

🎙️ Listen to the full Dutch episode on mennoenerwin.nl — your monthly guide to nature, science, and wonder.

We now have three publications:

Dutch podcast on wednesday
Nieuwsbrief NL → dutch newsletter
Newsletter ENG → same newsletter but in english

You can change what you will receive in your substack email from us in the bottom manage subscription or go to the link https://menno-en-erwin.substack.com/manage-subscription

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Newsletter #194 🌫️ November — The Month of Mist

Erwin Balkema — Sun, 09 Nov 2025 08:35:13 GMT

🌫️ November — The Month of Mist

A month that heralds winter, yet still shows the exuberance of autumn.

When the sun breaks through, the skies can be at their most beautiful — clear, radiant, and luminous. We may take that soft Dutch light for granted, but painters, travelers, and anyone with an eye for beauty notice its extraordinary glow.

Poplars, maples, and birches have already lost their leaves, but oaks still display a rich palette of colors. Mushrooms remain plentiful, and we’re often surprised by a late second bloom — of hawkweed, gorse, or the ever-brave daisy. Our hardy resident birds quarrel over their territories, while most winter guests have already arrived. When the skies fill with geese, you know the cold is near.

We can expect about five frost days, though the average temperature now hovers above 7 °C. Ten degrees by day is normal — yet twenty is no longer rare. Rain is back too: 80 mm this month is quite usual. With chill and humidity comes fog, hence the nickname “the month of mist.” It sounds far gentler than the older, grimmer names — the month of slaughter or blood month. Perhaps, in modern times, we might rename it pumpkin month or chestnut month.

🌿 The Quiet Beauty of Ivy

The humble ivy is an overlooked marvel this time of year. “I never see ivy in bloom,” people often say — and for good reason: ivy must be several years old before it produces its elegant clusters of yellow-green flowers, often high above eye level. And high they can go — up to fifteen meters!

Let’s also dispel a myth: ivy does not harm trees or walls. Its tiny rootlets cling for support but don’t penetrate bark or brickwork, nor do they draw nutrients from their host. Tall trees such as oaks and birches even shelter ivy, which in turn replaces mosses and lichens on their trunks.

The flowers offer nectar and pollen to late-flying bees, wasps, hoverflies, and butterflies like the Holly Blue. In early spring, the black berries provide welcome food for starlings, blackbirds, and wood pigeons — though they are poisonous to humans. Ivy also offers precious shelter for nesting birds and overwintering butterflies such as the Brimstone and Comma.

🍂 The Fungal Cleanup Crew

Those fallen leaves that clog every garden path? In nature, they meet their match. Countless “saprotrophic” fungi get to work decomposing them — from delicate ink caps suddenly appearing overnight to the stately boletes that form symbiotic bonds with trees.

🐦 Life Among the Birds

Is November a time of rest in the bird world? Not quite.

Many resident species still sing surprisingly energetically — robins, wrens, blue tits, and great tits defend their patches, just as jays, great spotted woodpeckers, and green woodpeckers do. Meanwhile, the winter guests busy themselves foraging: redwings, siskins, goldfinches, and, this year, large flocks of chaffinches. That abundance may well be thanks to the rich crop of acorns and beech nuts.

🦋 The Little Winter Moth

A small yet fascinating insect of the season: the Winter Moth.

It survives on the energy it stored as a caterpillar. The males take flight only after the first frosts; the eggs hatch in early spring, just in time to feed our nesting birds such as chiffchaffs and other migrants. Climate change has disrupted this timing — caterpillars now often hatch before the new oak leaves appear. Yet evolution is quick to adapt: the latest-hatching larvae are becoming the winners of this new rhythm.

🌰 Chestnuts, Acorns, and Autumn’s Harvest

For mammals, it’s still harvest season — berries and nuts abound.

The smooth horse chestnut, though inedible to humans, makes perfect playthings for children and tasty treats for wild boar. You can spot the tree easily by its large, hand-shaped leaves of five to seven lobes.

The sweet chestnut, on the other hand, bears narrow lance-shaped leaves and nuts hidden in spiny husks, each with a tuft of hair on top. Delicious when roasted or pureed into chestnut cream — but don’t be greedy, for squirrels, jays, crows, mice, boar, and countless insects love them too.

🍁 November Field Notes & Ideas

1️⃣ Is November truly the “month of mist”? Keep a mini log: record the highest and lowest temperatures this month.

2️⃣ Search for blooming ivy — a quiet wonder few ever notice.

3️⃣ Gather horse chestnuts (the smooth ones) and craft funny little figures from them.

4️⃣ Roast sweet chestnuts (the spiky ones with a tuft) — but check they’re not moldy first!

5️⃣ Observe which winter visitors are in your area this year. Are there really as many chaffinches as reports suggest?

Written for those who still notice the subtle colors of November, the scent of wet leaves, and the quiet rhythm of life preparing for winter.

🎙️ Listen to the full Dutch episode on mennoenerwin.nl — your monthly guide to nature, science, and wonder.

We now have three publications:

Dutch podcast on wednesday
Nieuwsbrief NL → dutch newsletter
Newsletter ENG → same newsletter but in english

You can change what you will receive in your substack email from us in the bottom manage subscription or go to the link https://menno-en-erwin.substack.com/manage-subscription

Blijf op de hoogte!

je kan je subscripties wijzigen zodat je alleen de engelse of nederlandse newsbrief ontvangt hier https://menno-en-erwin.substack.com/manage-subscription

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Newsletter #193 The Core of Science: Trusting Critical Engagement with Knowledge

Erwin Balkema — Wed, 05 Nov 2025 08:02:05 GMT

The Core of Science: Trusting Critical Engagement with Knowledge

In many places, the appreciation for scientific knowledge is under pressure. In the Netherlands, scientists still fare better in terms of public trust than journalists or politicians. In fact, trust in science has slightly increased recently.

But there is a divide. In 2025, one-third of the public expresses strong trust in science, while 15 percent gives science a failing grade. Only 20 percent of the public trusts how journalists report on science. And when it comes to how politicians deal with scientific knowledge? Fewer than 10 percent have confidence in them. This is what happens when politicians cherry-pick scientific results, fail to cope with uncertainty, or—worse—simply don’t understand how science works at all.

Science is about asking questions and figuring out how to answer them. That requires research, and accepting outcomes—even when they’re unexpected or ambiguous. Above all, science means being open to critique.

Sociologist Robert Merton proposed several principles that good scientific results should adhere to:

Knowledge must be public and shared;
It should be universal, acquired independently of the researcher’s personal background;
It must be disinterested, not dependent on personal or group interests;
Both methods and results must be open to review and criticism by fellow scientists.

Later, the principles of originality and sincerity were added. Even though scientific knowledge is the best we have, each of these principles comes with limitations.

When national security or commercial interests are at stake, the openness of scientific knowledge can quickly be threatened. Such knowledge—especially when formalized in patents—can easily end up locked away. The idea of universal and independent knowledge becomes problematic when it’s obtained under unethical conditions. This has, sadly, been the case in experiments involving human subjects.

Even the disinterestedness of science has limits. While outcomes shouldn’t be skewed by personal motives, it’s naïve to assume that scientists themselves have no stake in their research. On the flip side, we should not erase the role of the individual researcher either.

One of the most important safeguards remains the critical evaluation of scientific work by peers. Through peer review, publications are assessed before being accepted. Two additional demands have been introduced more recently: originality, to prevent plagiarism; and honesty, as emphasized by philosopher Jürgen Habermas, to prevent fraud in data collection and authorship manipulation.

It’s essential that the scientific community remains self-critical. Scientific insights evolve—especially when new data or methods become available. These new techniques must themselves also be scrutinized. Knowledge doesn’t always shift instantly—and that’s a good thing. Building and refining theories requires caution. However, clinging too long to outdated paradigms can be damaging. As science philosopher Thomas Kuhn once cynically remarked: sometimes retirement or death is the best guarantee of a paradigm shift.

Today, science faces serious challenges. Funding is a chronic issue. The process of publishing reliable, accessible research is increasingly undermined by commercial interests. Accountability to society is essential, especially in interpreting and applying scientific results.

But more threatening than all of this is the global political interference in science. Inconvenient knowledge is being denied, datasets are destroyed, international collaboration is sometimes prohibited, and entire fields of study are being dismantled if they don’t suit political agendas. Ignorance threatens to take over. And if humanity disappears, it may be despite all our scientific progress.

Five Tips for Navigating Scientific Knowledge

Wikipedia usually cites sources—always check them.
Thanks to open access, peer-reviewed scientific papers are increasingly free to read. Try university library sites or the Dutch Royal Library.
Be skeptical of press releases—even those from universities.
News coverage is often biased toward what’s dramatic or newsworthy.
The word “scientific” is not protected—it guarantees nothing.

We now have three publications:

Dutch podcast on wednesday
Nieuwsbrief NL → dutch newsletter
Newsletter ENG → same newsletter but in english

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Newsletter #191 🍃 The Best Tea Is Sold by the Kilo

Erwin Balkema — Fri, 17 Oct 2025 15:42:50 GMT

🍃 The Best Tea Is Sold by the Kilo

🍵 Tea is only tea if it says Camellia sinensis on the label.

That’s the name of the tea plant, mainly cultivated in China and India, but also in Indonesia, Kenya, Sri Lanka, Persia, and Turkey. Alongside coffee, true tea is the most consumed hot beverage in the world. Tea helps lower blood pressure and contains many beneficial compounds. But it’s a myth that tea contains no caffeine — it’s simply about half the amount of a cup of coffee.

🌿 The rise of herbal “teas” (like rooibos or chamomile) blurs the statistics on tea consumption. Yet with a global production of nearly five million tons, the true tea plant easily wins. Drying and oxidizing the tea leaves produces black tea; without oxidation, it becomes green tea.

🥇 Among the top varieties, aside from Assam (high in caffeine), Darjeeling — grown at the foothills of the Himalayas — is regarded as the “champagne” of teas.

🌍 The Tea Campaign

💡 Forty years ago, a Berlin professor launched the inventive “Teekampagne” (Tea Campaign). Growers receive a fair price, cultivation has become organic, and consumers pay less for top-quality first flush Darjeeling than for mediocre supermarket tea.

📦 How is that possible? By selling tea in kilo-sized packages — encouraging people to drink tea more often.

👨‍🏫 In 1985, economics professor Günter Faltin began a student project to create an ethical enterprise. He had studied the issues surrounding tea production in India and the complex supply chain between the plantations and European consumers.

💰 In Darjeeling, even in the best growing regions, farmers and pickers were poorly paid. The chain was full of intermediaries — auctions, exporters, importers, wholesalers, supermarkets, and retailers — before the tea reached the drinker, who had been trained to buy tea bags or small 100-gram packets.

🍃 Chemical pesticides were still widely used, and care for the environment was seen as a Western luxury concern. Only after a devastating landslide in 1968 did reforestation gain any real attention.

🌏 In the end, the Tea Campaign succeeded in convincing growers to join a fair-trade model, becoming the largest buyer of Darjeeling tea in the world.

🌳 More teas were added to the program — all organically grown, with strong environmental care (over 3.2 million trees planted), fair prices for pickers, direct import from plantations to Europe, and direct sales to consumers. The larger the package, the better the deal.

🏺 How Tea Is Made

☀️ Tea harvesting is a labor-intensive process, and so is production — especially for black tea. The young leaves must first wither.

🌀 Then moisture is removed by rolling the leaves between flat presses. Tea develops its aroma and color during oxidation — a delicate process where warm, humid, oxygen-rich air between 27 and 29 °C is circulated through the leaves.

🔥 Oxidation is stopped by heating and drying. From one kilo of fresh leaves, only about 200 grams of black tea remain. For green tea, the oxidation step is skipped entirely.

🧪 Besides caffeine (also called theine), tea contains fluoride (good against tooth decay) and antioxidants that help reduce the risk of type 2 diabetes and stroke.

⚕️ Tea was first introduced in the Netherlands as a medicinal drink. Later it became a luxury product for the wealthy, but by the 18th century it was widely appreciated across all social classes.

☕ The rivalry with coffee continues to this day. Coffee still leads, but about 70 % of the Dutch population now considers themselves tea drinkers.

💡 Tips for the Tea Drinker

1️⃣ Use good, soft water — preferably filtered or low in lime. That’s the secret behind every good cup of tea.

2️⃣ For black tea: let it steep for only 3–4 minutes in just-boiled water, ideally in a tea infuser that gives the leaves room to move.

3️⃣ For green tea: use slightly cooler water, between 70 and 85 °C, depending on the variety.

4️⃣ Herbal tea isn’t a protected term — most are harmless, but so-called slimming teas are best avoided.

5️⃣ Look for fair-trade and certified organic labels — otherwise, pesticide levels can be shockingly high.

We now have three publications:

Dutch podcast on wednesday
Nieuwsbrief NL → dutch newsletter
Newsletter ENG → same newsletter but in english

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Newsletter #190 What’s That Shrill Squeaking Around the House at Night? 🐭✨

Erwin Balkema — Mon, 13 Oct 2025 07:28:59 GMT

What’s That Shrill Squeaking Around the House at Night? 🐭✨

Chances are, a common shrew is scurrying through your garden, making its presence known. The common shrew is the most widespread shrew species in our country. Only on Vlieland and Terschelling do they have to do without them.

Despite their name, shrews are not actually mice — they belong to the insectivores, like moles and hedgehogs. What is true, is that they have a pointed, very mobile snout. Another frequent relative is the forest shrew, which looks quite similar at first glance. Yet, tens of millions of years separate the two species.

One belongs to the white-toothed shrews (subfamily Crocidurinae). These shrews, including the common shrew and the field shrew, are mostly nocturnal. When resting — especially in the morning or during winter — they can lower their body temperature to below 18°C.

This kind of daily mini-hibernation is called torpor.

The other lineage, around 20 million years older, are the red-toothed shrews (Soricinae). In our country, this group includes the forest shrew, the water shrew, the pygmy shrew (an adult weighs only 5 grams!), and the bicolored white-toothed shrew.

These species, with their orange-edged sharp teeth, are always warm and active — day and night — following a steady rhythm of one hour active, one hour resting.

Small but Intense ❤️‍🔥

Shrews are tiny mammals — none of the Dutch species weighs more than 15 grams. That means they lose heat quickly and have an extremely high metabolic rate. Their oxygen consumption is huge, their heart rate can reach up to 1,000 beats per minute, and their energy needs are sky-high.

The body temperature of red-toothed shrews averages 38.5°C, while white-toothed shrews run about two degrees cooler. All in all, they live fast and die young — rarely older than two years.

It’s a remarkable evolutionary story: two completely different strategies to survive such a demanding metabolism. One: stay active around the clock. The other: adopt a nocturnal rhythm and drop body temperature by over fifteen degrees during rest. Both have been successful for tens of millions of years.

Not Primitive at All 🧬

The idea that shrews are “primitive mammals” is simply wrong. They appeared 30 million years after the dinosaurs went extinct. It’s true that during the age of the dinosaurs, only small, “shrew-like” mammals survived by hiding in the night — but as we now know, they were not related to our modern shrews.

Diet and Predators 🐞🐍

Shrews eat mainly animal food — spiders, slugs, woodlice, worms, and insects, including larvae like leatherjackets (the underground larvae of crane flies). But they won’t shy away from a young mouse or a small frog either.

The water shrew, with its dark glossy coat, always lives near water and even eats small fish. On average, shrews consume their own body weight in food every day.

They have few predators — mostly tawny owls, barn owls, stone martens, foxes, and occasionally even wolves.

Most animals are deterred by their strong odor. Cats will catch and kill them, but never eat them — instead, they proudly bring them home as “gifts.” They’re rarely thanked for it.

Those Shrill Sounds 🔊

The high-pitched squeaks shrews make (some even use ultrasonic frequencies for echolocation) are thought to serve primarily for communication — and maybe also as a warning: Watch out, cats nearby! Or perhaps: Watch out for their owners.

💡 Observation Tip

1️⃣ Listen carefully at night.

2️⃣ Remember: catching or killing shrews is strictly forbidden — they are a legally protected species. We now have three publications:

Dutch podcast on wednesday
Nieuwsbrief NL → dutch newsletter
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Newsletter #188 Is laughter healthy?

Erwin Balkema — Sun, 28 Sep 2025 08:24:03 GMT

Is laughter healthy?

In the Middle Ages, laughter was considered the work of the devil. Later on, Calvinists also had their reservations about humorists who made people laugh, especially when it came at the expense of clergymen. These days, you can safely book a laughter therapy session or practice laugh yoga. The idea that laughter is healthy seems to have gained ground

There isn’t actually that much solid evidence for it. Unless you count the fact that the body releases pain-relieving substances like endorphins and dopamine when we laugh. Smiling and laughing also help to establish social bonds. Most laughter happens when we play (including tickling), something we share with many animals—from apes to birds, cows, seals, elephants, and even foxes. Humans, however, also laugh frequently out of schadenfreude, at bad jokes, or at our own clumsiness. That seems to be far less common—if present at all—among animals.

Humans have developed a kind of grammar of laughter. It consists of a series of repeated, staccato sounds. Only the first and last syllable can differ. “Hahohaho,” for instance, is not an acceptable laugh, but “hohoho” or “hihihiha” are. Primatologist Jan van Hooff may have spent too much time observing apes, but he concluded that humans laugh in a very peculiar way: We begin with a salvo of exhaled barks, mouths wide open. Then we end up in a cramped state: “dying of laughter.” After a squealing in-breath, we launch into another salvo. According to him, our fellow apes also have a sense of humor, often laughing when they trick one another or engage in playful mischief.

For us, laughter always seems to have a double character. Alongside its role in signaling friendly intentions during encounters, it can quickly slip into the nastier realm of ridicule. As Thomas Hobbes wrote in the 17th century: “The grimaces called laughter are nothing else but sudden glory arising from some sudden conception of eminency in ourselves, by comparison with the infirmity of others, or with our own formerly.”

Humor, then, can come from outside us, in the form of jokes or play. The most universally accepted kind of humor, in my (admittedly personal) opinion, is self-mockery. Yet laughter can also run completely out of control, as in a fit of the giggles. In extreme cases, it can even be fatal. Philosophers have spilled endless words on laughter, spinning wild ideas about its cause and function—rarely connected to the biological mechanisms of breathing and facial muscles that must, somehow, be involved.

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The simple claim that laughter is healthy is gradually gaining some scientific support. It seems to reduce high stress levels, lower cortisol, and help blood vessels function more optimally. Perhaps the best thing about laughter therapy is that, if it works, it’s a very cheap treatment—or at least, it should be.

Tips when it comes to laughter

A cheerful expression (take a look in the mirror before entering a room) works not only for others but also positively affects you as the smiler.
A fake smile is quickly recognized.
TV shows with laugh tracks should be banned (or at least switched off immediately).
When making a joke, a touch of genuine self-mockery makes it stronger.
There’s little to object to about laughter therapy—except when it gets too expensive.

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We now have three publications:

Dutch podcast on wednesday
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Newsletter #187 Is tension good and stress bad?

Erwin Balkema — Tue, 23 Sep 2025 19:52:43 GMT

Is tension good and stress bad?

Both tension and stress can have healthy aspects. But generally, stress tends to be viewed as something negative. Of course, stress is simply the English translation of the Dutch word spanning. That doesn’t help us much. Stress is often described as a physical reaction to external stimuli and situations that are perceived as threatening. These bodily reactions are not specific to the type of stimulus.

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Acute stress triggers the production of adrenaline in the adrenal medulla. This causes your heart rate to rise, your breathing to accelerate, your hands to sweat, and your body to enter a state of heightened alertness. If stress persists, production of hormones such as cortisol from the adrenal cortex begins. Energy is mobilized, while your immune system is suppressed. Over time, that leads to damage.

How to get away from stress? Entire courses have been designed for it, books have been written, and much money is made. Breathing deeply is never a bad idea when it comes to stress.

The whole system of stress responses has, of course, a functional background. It works in both humans and animals in the same way. In a direct confrontation with a crisis situation—say, the threat of a rock wall collapsing, several enemies suddenly appearing, or your offspring being in danger—all alarm bells go off. Everything is geared toward a fast and hopefully effective response. That can be a matter of life and death, which is why natural selection strongly favors it. These responses sharpen your focus. The same happens just before a sports competition or a public performance. In such cases, people speak of positive stress.

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But when misery lasts longer, all available energy is used to try to escape from it. Understandable, but it comes at a price: it can weaken immunity, affect appetite, or undermine social skills. The result can range from vomiting, inflammation, and abnormal behavior to exhaustion and cardiovascular disease. And that applies just as much to you and your fellow humans as to pets, zoo animals, and wildlife.

The environment plays a big role. City dwellers react more strongly to negative stress, something that can even be measured in brain activity. Or perhaps it’s just that more “stress frogs” live in cities? In any case, a green environment helps reduce stress.

What to do about stress?

In the case of acute stress, the key is to prevent panic. You can do that by consciously focusing on your breathing. It also helps to practice and prepare for stress situations you may expect—and even write a protocol for them.

Chronic, long-term stress is more complicated. Where possible, you can try to avoid stress factors in the environment (noise, heat, harassment). But mental problems and workload are often not so easily removed. This is where many therapeutic approaches come in. These often involve things like time management, breaking problems down into smaller pieces, relaxation through activities ranging from yoga, pets, music, meditation, or painting, to sports. Simply having someone to listen can already make a big difference.

And sometimes, with severe, prolonged stress—whether recent or from the past—you must absolutely seek professional help. Trauma counseling requires expertise. Surprisingly effective treatments may exist, such as linking eye movements to the memory of a traumatic experience.

In any case: deep breathing is always useful, and often it helps to do it consciously for a moment, before handing control back to your automatic breathing pilot.

Tips for dealing with stress

In acute stress, try to focus on your breathing for a moment—this prevents panic reactions.
Acute stress situations are often foreseeable; think in advance how you want to handle them. Check if there are protocols, and if not, write them down for yourself.
Chronic stress must be addressed, especially if it leads to sleep deprivation, irritability, fatigue, and exhaustion. Seek help—and at least a listening ear.
Some problems will fade over time, but facing them and making them discussable often already reduces stress.
Walking in nature—and actually looking around instead of staring at your phone—is always a good idea.

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We now have three publications:

Dutch podcast on wednesday
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Newsletter #186 In the Shadow of Its Tail – The Red Squirrel

Erwin Balkema — Tue, 16 Sep 2025 19:49:07 GMT

In the Shadow of Its Tail – The Red Squirrel

The Greeks could hardly have chosen a more fitting name for this enchanting rodent. A true tree-dweller, these bushy-tailed creatures build their nests five to six meters high. They are picky about their surroundings: oaks must be at least forty years old, beeches even sixty, before a squirrel will accept them as a home. They prefer vast coniferous forests, or at least mixed woods without too many deciduous trees. Industrious as they are, they collect nuts, acorns, and pinecones to store for winter. Sometimes they forget a food cache, and in doing so, they help trees spread.

A real threat comes from the larger, stronger gray squirrel. This American intruder was introduced into England in the 19th century and has since made its way into other parts of Europe, including our own. The gray squirrel is not just a competitor for food: it can carry viruses that are harmless to itself but deadly to the native red squirrel. In English woodlands, the gray has already gained the upper hand. In the Netherlands, several exotic squirrel species were once kept as pets, but that is now forbidden, and the red squirrel is strictly protected. Occasionally, one may still come across an Asian red-bellied squirrel (our native red has a white belly).

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The Dutch red squirrel population has always fluctuated. Besides problems with viruses and the single-celled parasite Toxoplasma, food availability plays a big role: a poor autumn harvest often means high mortality the following winter. Natural predators are plentiful—polecats and foxes on the ground, pine martens and goshawks in the trees. Traffic also takes a heavy toll, and with the continued fragmentation of the landscape, the Dutch squirrel population has dropped by a third in recent years.

Still, the red squirrel has a vast range. With the exception of southern Spain and a few Mediterranean islands, it can be found across Europe and deep into northeastern Asia, north of the Himalayas. In the Netherlands, it is absent only in parts of Zeeland, the north of North Holland and Groningen, and the west of Friesland. The sight of a squirrel always brings joy—especially when one is lucky enough to watch it eat, holding its food proudly between its tiny forepaws, tail elegantly balancing, and those tufted ears perked upright. Moments like that can make a whole day.

Five Tips for Spotting Squirrels

Check waarneming.nl to see if squirrels have been spotted in your area—and add your own observations.
Squirrels are active during the day, especially after dawn and before dusk. They forage on the ground, often retrieving hidden food stores. At the first sign of danger, they can spiral up a tree in seconds or leap from tree to tree, balancing with their tails.
In winter, their spherical nests (30–50 cm across) are easy to spot in deciduous trees. Look at least five meters up in the canopy.
Feeding remains are another good clue: gnawed pinecones (especially the scattered scales), cracked hazelnuts, and nibbled acorns or beechnuts.
And if you’re unlucky and don’t spot one? The internet is full of wonderful videos to enjoy instead.

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We now have three publications:

Dutch podcast on wednesday
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Newsletter #183 ☀️ Skin & Sun — The Truth You Need to Know

Erwin Balkema — Sun, 24 Aug 2025 09:30:48 GMT

Agriculture Without Taboos

More than half of our country consists of agricultural land. Most of that is grassland—livestock farming, in other words. Land prices are skyrocketing, especially for agricultural land, because space is scarce. Traditional views on agriculture are increasingly under pressure. Holding on to current levels of meat and dairy production—much of it for export—is becoming unsustainable due to high fixed costs and environmental damage. That also applies to the continued import of soy and fertilizer, and, admittedly to a lesser extent, the use of pesticides.

An alternative approach, such as extensive and organic circular farming, actually requires more, not less land. Our fear of any form of genetic technology also puts us at a disadvantage. The system will grind to a halt if we don’t explore new options—particularly if we want to safeguard biodiversity and ensure economically viable food production.

The development of new technologies could be part of the solution. Factory-based, vertical plant production offers spatial advantages by using plant walls. It also shortens the distance between producer and consumer, and allows for far more efficient use of water, energy, and nutrients.

Another path is the controlled application of modern molecular genetic techniques. Take CRISPR-Cas, inspired by how bacteria fight viruses: it allows us to precisely cut or replace pieces of genetic material. Applications have already been developed to make crops more resistant to salt and drought—two pressing climate issues—as well as to certain plant viruses. If research confirms that there are no unwanted side effects, this could significantly reduce our reliance on pesticides, which is still far too high.

Biologist Hidde Boersma, who calls himself an ecomodernist, advocates for many of these arguments. He fiercely criticizes both the political left and right, especially regarding spatial constraints. His view calls for a strict separation between agriculture and nature—a stance that somewhat overlooks how biodiversity actually works. Much of current farming remains blind to its ecological context. For instance, raising dairy cattle on peatlands is sheer madness—the land is literally burning beneath the farmer’s feet.

In general, we urgently need to reduce the land-use intensity and the unbounded export of meat and dairy. We simply can’t afford the ongoing loss of space and environmental quality. On the other hand, it’s an illusion to think we can grow the majority of our food solely through classical, organic methods.

We’ll need to connect nature-inclusive agriculture to new values like biodiversity and environmental quality—and be willing to pay for that. This also means developing new crops suited for salinized or re-wetted peat soils.

In short, the future may lie in a threefold strategy:

Technological crop and lab-meat production
A more modest, classic agriculture that ditches pesticides, soy imports, and synthetic fertilizers
Nature-inclusive farming that contributes to both food production and livability, alongside space for untouched nature

Five Consumer Tips for Smarter Food Choices

Reduce your meat and dairy consumption – it won’t do you any harm
Eat seasonal fruits and vegetables – and don’t import green beans from Africa
Know your producer – buy local or try ‘crowdfarming’
Organic food feels good – it’s more expensive, but often tastes better
Read labels carefully – prefab food is convenient but usually less healthy

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We now have three publications:

Dutch podcast on wednesday
Nieuwsbrief NL → dutch newsletter
Newsletter ENG → same newsletter but in english

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Newsletter #181 ☀️ Skin & Sun — The Truth You Need to Know

Erwin Balkema — Sun, 10 Aug 2025 19:56:10 GMT

☀️ Skin & Sun — The Truth You Need to Know

Your skin is your largest organ — your shield against the outside world, and a vital regulator of temperature and water balance. But sunlight, and the ultraviolet (UV) light it brings, is both friend and foe.

The good: Sunlight triggers vitamin D production, vital for strong bones, healthy immunity, and more.
The bad: UV light dramatically raises your risk of skin cancer — even if you have darker skin. Tanning does not protect you.

UVA vs. UVB — Why it matters

UVA (longwave) penetrates deep, causing skin aging, loss of elasticity, dark spots, and some cancers. It’s present year-round, and half gets through glass.
UVB (shortwave) hits the skin’s surface, causes sunburn, and is the main cause of skin cancer. It’s strongest midday in summer and at lower latitudes.

Evolution and skin color
Lighter skin evolved in low-UV areas to boost vitamin D. Darker skin evolved in high-UV zones to protect folate (vitamin B9) from being destroyed by sunlight. Both have strengths, but at every latitude, sunburn is harmful. Childhood burns greatly increase the risk of melanoma — a deadly cancer also linked to tanning beds.

The bright side
Moderate sun exposure is linked to lower heart disease risk, reduced cancer rates, better sleep, and a healthier biological clock.

5 Sun-Safe Rules

Avoid midday sun in summer without protection.
Clothing beats sunscreen; if using it, go for SPF 100 and reapply every 2 hours.
Fair-skinned in (sub)tropics? Extra caution — UV is high all day.
Darker skin still needs protection.
Enjoy the sun’s benefits — but never burn.

☀️ Bottom line: Sunlight is healthy — in moderation. Protect your skin, skip the burn, and soak up the benefits.

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We now have three publications:

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Newsletter #180 August – The Rich Month of Summer

Erwin Balkema — Tue, 05 Aug 2025 20:07:50 GMT

August – The Rich Month of Summer

August has traditionally been known as the harvest month. These days, much of the harvest is already in, thanks to extensive mechanization that—weather permitting—makes for a very swift process. The month is named after the first emperor of the Roman Empire, and he can consider himself honoured: August feels like the ultimate summer month. On average, it brings around 25 warm days (above 20°C), 8 true summer days (above 25°C), and in recent years, an increasing number of tropical days. The sun now shines about ten hours more than it used to, and rainfall has increased by roughly 25 mm—totalling 86 mm. Still, on average, August is slightly cooler than July. Due to shortening days, the sun shines 20 hours less than in July.

In the natural world, birds stand out in August mostly by moving on or flying away. For insects, however, August is peak season: many plants are still in bloom. Few new species begin flowering now, but among them are three troublesome exotic invaders from the Caucasus, the Americas, and Japan. Let’s talk about those.

The best-known is the giant hogweed—a towering member of the umbellifers, growing 2 to 3 metres tall with flower clusters up to 50 cm and leaves nearly a metre wide. Originally introduced from the Caucasus around 1900 as a garden plant, its spread exploded in the second half of the 20th century. The trouble lies in its sap, specifically the chemical furocoumarin, which—transmitted via stiff hairs on the leaves and stem—can cause severe burns when exposed to sunlight. Best to remove it before it flowers (see tips below), or let sheep and pigs devour it—they know what to do.

Then there’s common ragweed (Ambrosia artemisiifolia), a plant with highly allergenic pollen that can cause intense hay fever. It was first introduced around 1875 via hay from the US and is now mostly spread through contaminated birdseed. Thanks to climate change, it’s also slowly advancing northward. Standing 50–150 cm tall with deeply divided leaves (resembling mugwort), its drooping yellow flower clusters are the male parts releasing allergenic pollen. Besides gardens, it thrives on sandy farmland and wasteland.

The third invader may be the most stubborn: Japanese knotweed. Once a decorative import from Japan, it grows 1–3 metres tall, with large egg-shaped leaves, reddish stems, and small white to pinkish flowers. The real issue is its aggressive growth—just a tiny fragment of rhizome can regrow, crowd out other species, and even damage foundations and drainage systems. Complete excavation is the only solution. Pigs reportedly enjoy eating the roots, and there’s hope for a Japanese parasitic psyllid to help—if it doesn’t create new problems, of course.

Enough about the exotics. Another plant worth mentioning is ivy, which begins blooming now—not the showiest, perhaps, but incredibly important for insects in the months ahead. Thankfully, we can still enjoy our native hogweed and other umbellifers like Joe-Pye weed, spotted hemlock, valerian, and sweet William. They’re well worth a closer look—hoverflies, wasps, soldier beetles, and ladybugs are frequent visitors. Thistles still attract plenty of butterflies and insects too, as do evening primroses, purple loosestrife, and both hairy and common fireweed. Water lilies are still blooming, as is mallow. On the heathlands, common and cross-leaved heath are in bloom, accompanied by grasshoppers and digger wasps.

Bird-wise, August is a month of movement. Starlings and spoonbills gather in large flocks after the breeding season, while many of our nesting birds have already departed or are about to. Migrants from Scandinavia begin passing through, including ruff, greenshank, whimbrel, wood sandpiper, and green sandpiper. Brent geese, sanderlings, redwings, bramblings, and wigeons arrive to spend the winter. In short: autumn is already announcing itself.

🌿 Tips for August

Watch the bird migration! Use binoculars—or better yet, a telescope—on the North Sea coast, the Wadden Islands, or around the Veluwemeer.
Visiting heathlands? Keep an eye out for migrating raptors.
Make a checklist of which birds haven’t left yet, like lesser whitethroats, garden warblers, blackcaps, and common whitethroats—and note the true residents like the robin, wren, and our familiar tits.
Want to remove invasive plants? Prepare well (at the very least: gloves!), and try to dig out the entire plant, including roots and rhizomes. Avoid skin contact, especially with giant hogweed and ragweed.
Never dispose of invasive plant material in your green bin or compost heap—always put it with residual waste.

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We now have three publications:

Dutch podcast on wednesday
Nieuwsbrief NL → dutch newsletter
Newsletter ENG → same newsletter but in english

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Newsletter #179 The angular willowherb — who doesn’t know it!

Erwin Balkema — Wed, 30 Jul 2025 07:37:40 GMT

in dutch : Listen to the podcast

The angular willowherb — who doesn’t know it!

Anyone trying to remove weeds between the paving stones can sometimes face real dilemmas. Like with that beautiful, subtle plant, often around fifty centimeters tall, with narrow leaves resembling those of a willow and pointed pink flower buds that look promising even when still closed. Upon closer inspection, the plant turns out to be the angular willowherb (Epilobium tetragonum). Surprisingly, it belongs to the same family as the evening primrose and the often much larger hairy and common willowherbs. This weed is well worth a closer look, as becomes clear from the pocket guide Stoepplanten (Pavement Plants). In that guide, you’ll be amazed again and again—104 times, to be exact.

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The name angular willowherb does require some explanation. The Dutch word “wederik” (willowherb) refers to a willow-like plant. But in many parts of the Netherlands, the large loosestrife (Lysimachia vulgaris) also grows—a yellow-flowering summer plant with narrow leaves from the primrose family, once believed to have medicinal properties. Probably to avoid confusion, the name “bastard willowherb” was given to a genus of about two hundred plants in the evening primrose family. And the “angular” part of our plant’s name becomes clear as soon as you look at and feel the stem. The stem, which has two or four sharp ridges, cannot be easily compressed.

Our plant can be found on virtually every street in the city, often in dry and sunny spots, or against walls and in alleys. The plant is often slender and under thirty centimeters tall, but can also grow wide and up to a meter high. Once the plants have finished blooming in early autumn, silver-colored seed tufts emerge from the fruit.

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Interestingly, the numbers of this “weed” in our country appear to have increased dramatically since the beginning of the last century. Yet it’s debatable whether that’s really true. Its distribution used to cover the entire country as well. What has dramatically increased is the number of documented grid squares. Yes, interest in weeds is fortunately on the rise. Groups of enthusiasts are organizing excursions focused on what has come to be called pavement plants. To spark more interest and share information, they write the names in chalk on the sidewalk. The aforementioned Stoepplanten pocket guide was created by a local group from Breda, in collaboration with the Hortus Botanicus in Leiden. Each of the 104 entries is a fascinating story, from sidewalk grass to the common daisy—two examples of species that bloom all year round. We’ll definitely return to the topic of weeds again.

Five tips for learning more about pavement plants

Before you pull a weed out, take a photo with your phone and use the lens function to try identifying it.
Buy the Stoepplanten guide—an investment for life.
If that’s too much, at least look up background information online (e.g. floravannederland.nl or Wikipedia).
Check if there’s a pavement plant excursion near you (e.g. via IVN, KNNV, or a local working group).
Report your observations on waarneming.nl—this also allows you to check if the same species has been found nearby before.

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We now have three publications:

Dutch podcast on wednesday
Nieuwsbrief NL → dutch newsletter
Newsletter ENG → same newsletter but in english

You can change what you will receive in your substack email from us in the bottom manage subscription or go to the link https://menno-en-erwin.substack.com/manage-subscription

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Newsletter #178 What is life? And is that a question for a biologist?

Erwin Balkema — Tue, 22 Jul 2025 19:20:09 GMT

in dutch : Listen to the podcast

What is life? And is that a question for a biologist?

It might seem a bit strange, because a biologist literally studies life. So you would expect them to know the answer… Even though most people have a general sense of what life is, it’s actually not an easy question to answer. According to some, reproduction is an essential characteristic of life. But then, does a neutered dog not count as alive? All living things are made of cells—but is that enough as a definition? Dead cork tissue also consists of cells, after all.

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At school, you probably learned the seven characteristics of life—do you still remember them? But even those have limitations and certainly don’t apply to the entire life cycle. And what about viruses? Most biologists would draw the line there, as a virus always depends on other life forms to function. That one simple, all-encompassing definition of life seems far away. But is that a problem?

Perhaps not. It also depends on the perspective from which you approach life. Take thermodynamics, for example. From a physics perspective, life could be described as a temporary resistance against the law of increasing disorder (entropy). A chemist might mutter something like: “a combination of many different chemical systems that together are more than the sum of their parts” (as Nobel Prize winner Ernest Rutherford once suggested)

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Life is often described based on what a living system must do and be able to do. The core elements are that order must be maintained within the (cellular) body, and that there must be an exchange of substances and energy with the environment. Growth and development must also take place, along with responses to external stimuli. An environment to which the life form can adapt. That sounds a lot like the list of seven you learned in school:

breathing, feeding, excreting, moving, growing, sensing, and reproducing.

The challenge is that a definition of life should ideally draw a clear boundary that applies to all life forms—plants, animals, fungi, algae, and bacteria. And that’s only the life we know of on Earth. What about extraterrestrial life? We can only speculate about that for now. We are made of stardust, but that doesn’t tell us very much either.

In the end, it may be more interesting to look at how life develops. The interaction of chemical compounds leads to the formation of complex molecules, as we also see in viruses. And to their credit, viruses are perfectly capable of reproducing and surviving—although they always need other life forms to do so. Independence is the next step, and the formation of a cell—and later multicellular organisms—was certainly a major one.

And so, we can describe the entire Darwinian evolution of life forms, which, at least for life on Earth, has resulted in a remarkably robust and well-founded framework. All in all, chasing after one conclusive definition of life is of limited satisfaction—though perhaps inspired by the question of what happens when death enters the picture.

The question of how life on Earth actually began is at least as intriguing, but we’ll save that for another time.

Five prompts to reflect further on what life is:

What makes the difference for you between something being alive or not?
And what exactly changes at the moment of death?
What do you think alien life would look like?
An inspiring article from the NEMO science museum (in Dutch):
https://www.nemokennislink.nl/publicaties/je-herkent-leven-als-je-het-ziet-maar-wat-is-het/
Or check out NASA’s resource:
https://astrobiology.nasa.gov/research/astrobiology-at-nasa/exobiology/

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We now have three publications:

Dutch podcast on wednesday
Nieuwsbrief NL → dutch newsletter
Newsletter ENG → same newsletter but in english

You can change what you will receive in your substack email from us in the bottom manage subscription or go to the link https://menno-en-erwin.substack.com/manage-subscription

Blijf op de hoogte!

je kan je subscripties wijzigen zodat je alleen de engelse of nederlandse newsbrief ontvangt hier https://menno-en-erwin.substack.com/manage-subscription

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Newsletter #177 Microplastics: Our brains now contain more than two plastic bags worth

Erwin Balkema — Tue, 15 Jul 2025 13:13:51 GMT

in dutch : Listen to the podcast

Microplastics: Our brains now contain more than two plastic bags worth

It once seemed like such a fantastic invention: the development of plastics. Linking simple chemical compounds from the hydrocarbon group into so-called polymers. The applications were—and still are—endless: in textiles, cosmetics, car tires, the packaging industry, construction. But by now, we’ve begun to see synthetic plastics in a different light. Their breakdown products, in the form of microplastics, are everywhere: in the oceans, on Antarctica, and in virtually all plants and animals on Earth. And recently, it was found that the human brain contains about five grams of microplastics. In dementia patients, that number is five to six times higher. Does that indicate harmful effects? That remains a topic of ongoing debate.

There are two additional problems associated with microplastics. Most are created by the weathering of synthetic polymers, but a quarter are produced directly as tiny granules: microbeads. These are used as fillers and abrasives in cosmetics, toothpaste, and industrial applications. The second issue is that many microplastics are now breaking down even further into nanoplastics, smaller than a thousandth of a millimeter. These tiny particles can penetrate intestinal and lung tissue, and even pass through the blood-brain barrier.

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An estimated 200,000 tons of microplastics float in the world’s oceans. A Dutch study from July this year showed that the North Atlantic alone contains ten times as much nanoplastic—about 2.7 million tons, found both at the surface and at depths of up to 1,000 meters. According to researchers, this shocking amount cannot be cleaned up. But it does explain where the massive amount of plastic produced on Earth has ended up—until now, we couldn’t account for it. “A large part is now drifting through the oceans as minuscule particles.”

Most microplastics consist of polyethylene waste, but also many other compounds—from PET (as in PET bottles) to styrene-butadiene, i.e., synthetic rubber. Especially due to increasingly heavy SUVs, massive amounts of micro-rubber particles end up in the environment.

Today, micro- and nanoplastics are in our drinking water, in plants and animals, and in much of our food—in fish, honey, and beer, to name a few. Many particles are also now airborne. In national parks in the western United States, 1,000 tons of plastic per year were found falling from the sky in 2020.

Are these small plastic particles harmful? For now, we only have suspicions and early indications. In fish and shellfish, they disrupt reproduction. Research in Groningen showed that lung tissue stops growing due to small nylon particles. Immune cells seem to struggle with their defensive functions due to nanoplastics. There’s even a chance that dangerous viruses may hitch a ride on these nanoplastics.

This year, a major comparative study was published on the presence of microplastics in deceased individuals. Over eight years, the amount of particles in the liver and kidneys, but especially in the brain, increased significantly. In dementia patients, the increase was dramatic—about 25 grams of microplastics in the brain.

What can we do? Some hope lies in micro-organisms that might clean up our mess, but that could be an illusion. A shift to biodegradable biopolymers—which may be more expensive but break down without harmful residues—seems the logical path. For some easily avoidable uses, like microbeads in cosmetics and toothpaste, an immediate ban is inevitable. Strong efforts must be made to find alternatives, as the current situation is becoming untenable. Finally, we must rethink waste management—clean up where possible, and fully incinerate the rest, ideally with ultrafilters to capture what’s left.

Five Tips to Avoid Microplastics

Don’t drink water from plastic bottles; don’t give babies drinks from plastic bottles either.
Avoid plastic packaging—use paper bags and buy loose vegetables.
Protest against supermarkets’ packaging obsession (like cucumbers in plastic condoms). Watch for unnecessary packaging and complain.
Rinse vegetables, fruit, and any food that has been wrapped in plastic.
Avoid toothpaste or cosmetics that contain microbeads.

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We now have three publications:

Dutch podcast on wednesday
Nieuwsbrief NL → dutch newsletter
Newsletter ENG → same newsletter but in english

You can change what you will receive in your substack email from us in the bottom manage subscription or go to the link https://menno-en-erwin.substack.com/manage-subscription

Blijf op de hoogte!

je kan je subscripties wijzigen zodat je alleen de engelse of nederlandse newsbrief ontvangt hier https://menno-en-erwin.substack.com/manage-subscription

Available for iOS and Android

Newsletter #176 July, the Hay Month?

Erwin Balkema — Sun, 06 Jul 2025 03:48:10 GMT

in dutch : Listen to the podcast

July, the Hay Month?

Traditionally, the warmest month of the year is called the hay month. Nowadays, that really only applies to bluegrass meadows and other natural pastures. Most farmers are already working on their second or even third grass harvest. July, named after Julius Caesar, is the month of butterflies and thistles, blooming wild honeysuckle and flowering swanflowers—just to name a few beauties.

July has always had the most sunshine hours of the year. That number has increased in recent years, from 210 to 223 hours per month, resulting in a rise in average temperature of 1.6 degrees Celsius. The number of tropical days (above 30 degrees) varies year to year. A now-classic result of our changing climate is the increase in rainfall during July in the Netherlands, from 67 to 79 millimeters. Due to evaporation, the positive effect of this rain on nature is doubtful.

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Potatoes and tomatoes are in bloom, and wherever they get the chance, poppies and cornflowers bloom along the field edges. In the water, water lilies—the largest flowers in the country—are blooming. Reeds bloom too, and a special plant, the water soldier, attracts the rare green hawker dragonfly once it surfaces and flowers. On the salt marshes, July is peak bloom season, with species like sea lavender, orache, and samphire. In the dune valleys, reed orchids and grass-of-Parnassus bloom. Sometimes, you search in vain for once-common plants like the devil’s-bit scabious—a now-rare species of poor grassland. One memorable case is a lawyer who dismissed objections to excavation by calling the plant “common,” likely using an outdated flora guide.

The number of flowering plants in July continues to rise—about 150 species are added to the season’s floral chorus. July is a rich month for insects: black-and-yellow caterpillars of the cinnabar moth feast on toxic ragwort. Other striking yellow bloomers include mullein, evening primrose, tansy, and various hawkweeds. Moths, bugs, and dragonflies are often highly specific about their host plants, while pollen-collecting bumblebees and solitary bees are less picky.

It’s also the time of year for many young, clumsy birds learning to fly. The reed warbler still sits on its nest, and even higher up, the stork has become a familiar sight in recent years. Moorhens, blackbirds, and blue tits attempt a second brood. Birds sing less and less: the wren, robin, and chaffinch still hold strong, but the chiffchaff and willow warbler are already preparing for or dreaming of their southern migration.

Tips for July

Visit the Wadden Islands or coastal dunes this month: it’s peak blooming season.
On sunny days, look for dragonflies and damselflies near ponds and ditches (check the Butterfly Foundation’s website).
Observe which insects visit which flowers—from butterflies to bees, wasps, and hoverflies (use ObsIdentify).
Attend a moth night where hundreds of species gather at illuminated white sheets—experts are often present to help identify them.
Keep a daily bird list of your area—it helps track which species leave first as the migration begins.

Leave a comment

We now have three publications:

Dutch podcast on wednesday
Nieuwsbrief NL → dutch newsletter
Newsletter ENG → same newsletter but in english

You can change what you will receive in your substack email from us in the bottom manage subscription or go to the link https://menno-en-erwin.substack.com/manage-subscription

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Newsletter #175 Youth, Nature, and Ecology

Erwin Balkema — Tue, 01 Jul 2025 05:38:11 GMT

in dutch : Listen to the podcast

Youth, Nature, and Ecology

If there’s one group with a vested interest in nature and ecology, it ought to be the youth. The sense of certainty about our environment seems to be slipping away—especially for those thinking seriously about the future. A healthy natural world, clean water, fresh air, and unpolluted soil all appear to be vanishing at an alarming pace. PFAS and microplastics, unprecedented species extinction, habitat destruction, and rapidly accelerating climate change—these are the keywords of the coming generation. Schoolbooks with well-meaning texts about the importance of ecology contribute little.

The extraordinary luxury and prosperity in which most of our young people live is taken for granted—as if it’s something they’re naturally entitled to. Young people may take shorter showers now, but they’ve largely let go of flight shame—if they ever felt it at all.

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Two underlying issues are at play: a loss of contact with nature and a lack of what our German neighbors call Bildung—a state of intellectual development driven by the desire to learn, and a willingness to invest time and effort to understand the world around us. Perhaps experiencing nature in our immediate surroundings offers a way forward. This is happening at some schools. Being amazed by weeds between the paving stones, delighted by bees and wasps, or enjoying the recognition of a bird nesting nearby. Nature sport—that’s what Jac P. Thijsse once called it.

Admittedly, in his time at the start of the 20th century, it was also just a small group that truly cared about this. Yet the interest was greater—nature albums from Verkade sold by the hundreds of thousands. Trade unions and precursors to the Labour Party provided nature education, founded nature centers, and organized nature excursions and holidays.

Nowadays, many people are still members of Natuurmonumenten or the Provincial Landscapes. But the engagement is becoming increasingly passive. Nature clubs like IVN and KNNV are struggling. Nature lovers are becoming more individualistic, relying on (often excellent) smartphone apps. To be fair, our own enthusiasm for field biology only came later in life. And that’s largely due to a lack of encouragement from our surroundings. Who takes you outside and shares knowledge about nature? What do parents do? Who at school?

The urgency of treating nature and our environment much better is crystal clear (and anyone who denies it is as foolish as Simon Rozendaal). To reverse the tide, we’d need to heavily invest in teachers’ knowledge. But biology as a subject has been removed from what’s called primary education. So natural science at elementary school is gone. As a result, students in teacher training (Pabo) often know nothing about nature—except for a few enthusiasts. Municipalities and schools now often bring in external experts from organizations like NME and IVN to patch things up. That’s great—but also a sad indicator of poverty. A population that doesn’t know its environment has little future. Correction: no future.

Five Tips for Parents to Reconnect Children with Nature:

Go outside with your children. Which birds do you hear? What plants grow on your street? Which mushrooms can you find nearby? What insects—ranging from butterflies to dragonflies to crane flies (which don’t sting, remember?)—do you encounter? Your smartphone can guide you.
Join a local landscape or nature organization like the Provincial Landscape, IVN, or KNNV. That way, you’ll at least bring nature-related information into your home.
Ask about nature education at your child’s school. What do the teachers know? And if it’s not enough, who do they bring in to help?
Check what your municipality is doing. Are there school gardens? Opportunities for excursions or discovery days outdoors?
Talk to your children about how essential clean drinking water and clean air are—now and in the future. How can you and your children prevent local pollution? How can you ensure food that is tasty, safe, and environmentally friendly?

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We now have three publications:

Dutch podcast on wednesday
Nieuwsbrief NL → dutch newsletter
Newsletter ENG → same newsletter but in english

You can change what you will receive in your substack email from us in the bottom manage subscription or go to the link https://menno-en-erwin.substack.com/manage-subscription

Blijf op de hoogte!

je kan je subscripties wijzigen zodat je alleen de engelse of nederlandse newsbrief ontvangt hier https://menno-en-erwin.substack.com/manage-subscription

Available for iOS and Android