The threat of global change for Arctic vegetation

Posted on October 26, 2026 by lembrechtsjonas

When standing on the top of a mountain in northern Scandinavia on a cold spring day, I find it easy to be impressed by the vastness and harshness of the Arctic. A wilderness that seems to fit the very definition of wilderness. But then, after a few minutes of awe, I’d turn around and see the road that brought me up to that mountain top. And those beautiful snowfields around me? The result of an almost snow-free winter, followed by a huge snowfall peak in April, substantially delaying the growing season. Even here, the wilderness is clearly changing.

It turns out there is simply nowhere remote enough to escape the tentacles of global change. Nowhere! And that matters for the plants and animals that have evolved to survive in these extreme environments.

In a new review paper in Ecology, we bring together current knowledge on how global change is already affecting biodiversity in cold-climate regions, from the Arctic and Antarctic to the highest mountain ranges. We focus particularly on plants and invertebrates: often overlooked, but essential for how these ecosystems function.

The paradox of cold regions

There is a reason many cold regions still feel so pristine. Compared with many other parts of the world, they have often faced less pressure from intensive land use, pollution and the direct exploitation of natural resources. Not everywhere, of course, but this relative lack of some human pressures has helped uniquely adapted plants and animals persist.

The catch? These regions are particularly exposed to two other drivers of global change: climate change and biological invasions.

Cold regions are warming rapidly, and the species living there face changing temperatures, altered snow cover and the myriad of downstream effects of those. For organisms adapted to the cold, there are limits to how much they can tolerate, adapt or move elsewhere. And for species already living on mountain tops or isolated polar islands, there may simply be nowhere else left to go.

But climate change isn’t the whole story. Biological invasions are another threat we need to take seriously.

As human activity brings more non-native species into cold regions, the barriers that once helped keep newcomers out can weaken. The road that brought me to that mountain top is one example. Tourism and scientific expeditions to Antarctica, for example, can also provide opportunities for species to hitch a ride towards places where they were previously absent.

The worrying part is that these pressures don’t act in isolation. Warming can make it easier for new species to establish, while biological invasions can further reshape ecosystems already experiencing environmental change. Together, they can have consequences that are difficult to predict, potentially threatening the unique biodiversity that makes cold regions so special.

Climate change and biological invasions are altering the very fabric of our cold-climate ecosystems, from the physiological level up to the species level

So what do we need to do?

Our review points to three important priorities.

  • We need to keep a much closer eye on what is changing. Long-term monitoring of populations and genetic diversity is still remarkably limited for many cold-region plants and invertebrates. Without a baseline, it is difficult to recognise changes early, let alone understand what is driving them.
  • We need to understand the limits of life in the cold. How much warming can a species tolerate? How do changing temperatures affect its growth, survival and reproduction? And how much variation exists between populations of the same species? Better physiological data will help us make more reliable predictions about which species are most vulnerable.
  • We need to get better at predicting ecological change. Which species are most at risk, which might be able to adapt or move, and where could new species establish? Answering these questions requires combining physiological data, long-term monitoring and a better understanding of how different global-change drivers interact.

There is another lesson here that is close to our hearts at the 3D Lab: where we measure environmental change matters. A weather station can tell us a lot about the climate of a region, but not necessarily what a plant experiences beneath a stone, inside a moss cushion or under a patch of snow. These small-scale differences can make the difference between surviving and disappearing and may offer refuges for some species as conditions change.

Cold regions can feel like another world, far removed from the places where most of us live. But that feeling of remoteness can be misleading. Global change reaches even these seemingly untouched landscapes, through changing climate, human activity and the species we move around the planet.

There is no escaping it. Nowhere.

Read the paper: Renault et al. (2026), Global change threatens the biodiversity of cold regions: Current knowledge and priorities for further research, published in Ecology.

https://doi.org/10.1002/ecy.70537

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How microclimate is changing at a different rate

Posted on October 21, 2026 by lembrechtsjonas

If you’ve been following my research for a while, you should know by now that microclimate warming rates can be very different from what our weather stations and climate models tell us. We’ve been discussing it for forests, mountains and backyards: the temperature that plants, insects and soil life actually experience doesn’t just differ from the regional average, it can also change at a different pace. It’s something I’ve been repeating on this blog for years, as a logical consequence of the existence of microclimate.

However, what we hadn’t told yet in much detail, is how that difference could come about. While we’ve seen a few great published examples (forest cooling, shrubification, urban expansion, …), a good overview of the mechanisms behind these different changing rates was still largely missing. And having those mechanisms sharp in our heads is quite important, as the implications of this phenomenon are quite substantial.

That knowledge gap has been filled now, with a new review in Global Change Biology, led by Caroline Greiser and written together with an international team spanning 12 countries (I had the pleasure of being among them). This one focuses on how it can be macroclimate change itself that drives different rates of microclimate changes as experienced by life on Earth, and how these micro-scale changes may, in turn, feed back into the regional and global climate system.

Change in microclimate maximum temperatures at Caerthillian Cove, Lizard Peninsula, UK (49.97° N, 5.21° W), from 1983 to 2015. Microclimate temperature changes were derived for each grid cell by linear regression on annual maximum air temperature (5 cm above ground). Interactions between terrain, vegetation, and weather caused local warming rates to diverge from the regional macroclimate trend (0.3°C over the ~3 decades). Three example locations illustrate strong warming (2.9°C), moderate warming (0.7°C), or even cooling (−1.3°C).

One headland, three warming rates

Let’s start with the example that, to me, says it all. Walk across the Lizard Peninsula in southern England (close to home for co-author Ilya Maclean and thus one of the most intensively modelled microclimates in the world, I’d say) and you pass from a spot that warmed by almost 3 °C over the last three decades to one that actually cooled by more than 1 °C. The regional average over the same period? 0.3 °C. Climate change, as it turns out, can vary quite substantially over just a few hundred metres.

It’s easy to think of climate change as a single number for a region, but the organisms we care about never experience those weather station averages. They live on one particular hillside, in one particular patch of forest. For them, the warming rate can be very different from the regional average, and that is a story we have largely been missing. The same is true for us humans, of course, which makes this a story that hits close to home.

All this implies a much wider range of warming rates than we are used to. You may have heard of Arctic amplification, the Arctic warming faster than the rest of the planet. This study suggests that such differences can play out on a much smaller scale still, from one valley to the next, depending on changes in vegetation and atmospheric conditions.

A shaded hillside will warm much more slowly than one exposed to the sun all day, as extremes get amplified. Picture from northern Scandinavia

So how is that possible?

The technical answer is that microclimate is the outcome of an energy balance at the land surface: sunlight comes in and is divided between heating the ground and the air, evaporating water, and being stored in soil and plants. Change anything in that balance, and places respond differently depending on their slope, vegetation, soil and exposure. Thanks to new data (including from remote sensing) and models, we are now able to decipher what that means for future microclimate trends.

The paper explores how climate change and microclimate change affect each other, through changes in vegetation and meteorological conditions.

Clouds play a surprisingly big role here, and are my personal favourite. Daytime cloud cover has been declining in many regions, in Europe by roughly 1.5 to 2% over two decades. That extra sunshine doesn’t land equally everywhere: sun-exposed slopes and open meadows catch it, while shaded slopes and forest interiors barely notice. As cloud cover decreases, the contrasts in a landscape are thus accentuated. Your south-facing hill will suddenly be much warmer, much more often in the year, and so warms at a substantially faster rate than the north-facing hill next to it.

My favourite figure from the paper. It shows intuitively how simple changes in meteorological conditions, such as the steepness of the relationship of temperature with elevation (a), or the frequency of cold air pooling (b), can totally change the warming rate.

Snow does something similar in colder regions. It insulates the ground from cold air and caps surface temperatures at 0 °C for as long as it lies there. In the simulations of a mountain landscape in the Pyrenees, snow cover shifted minimum temperatures by about 3 °C, almost an order of magnitude more than wind or air humidity. Less snow therefore changes local conditions all year round, and not equally everywhere. Soil moisture works in a comparable way: wet soils spend their energy on evaporation, dry soils on heating the air, so where soils dry out, temperature extremes can climb faster than the nearest weather station suggests.

Plants, finally, play a role as well. If they stop transpiring water to survive more frequent and intense drought spells, their cooling effect will be much reduced. Entire plant communities are also shifting due to climate change. In a simulation of a steppe taken over by shrubs and trees in Turkey, the hottest days cooled by up to 16 °C under dense cover, while open patches nearby became several degrees hotter. A small note of caution here: these simulations isolate single drivers to show the mechanisms, so read them as illustrations of how landscapes respond rather than as forecasts.

If there is one thing that really stands out from all of this, it is that there is no single culprit. Clouds, snow, soil moisture and vegetation each shift the energy balance a little differently from one spot to the next, and together they can pull neighbouring places apart quite substantially. For farmers, beetles and everything in between, those differences have real implications.

What this means for the future

Indeed, if the pace of warming differs so much over such short distances, so will its impacts on biodiversity and ecosystem processes. Some places may already be facing substantial changes in local climate conditions, while others haven’t even noticed that change is on its way. Solutions will therefore need to be much more tailor-made: the farmer on one side of a hill and the farmer on the other may well need completely different strategies against the changing climate.

That also makes climate adaptation a joint effort of climate science and ecology, two fields that have long worked in parallel but not always together. To work out which strategy fits where, we need ecologists and atmospheric scientists in the same room, speaking the same language. Much of the physics we need has been known for decades. What is needed now is the interdisciplinary collaboration to apply it.

And since this paper for now leaves out what we humans do to the landscape, through farming, forestry and urban design, there is a natural next question: how much do we ourselves shape these local warming rates? More on that soon!

Reference: Greiser, C., et al., Lembrechts, J.J., et al. (2026). Climate change experienced by life on Earth – drivers and mechanisms of future trends in microclimates. Global Change Biology. https://onlinelibrary.wiley.com/doi/10.1111/gcb.71140

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A glimpse from the field

Posted on October 14, 2026 by lembrechtsjonas

By Journey Verspeek – master student in the team

And there you are, in the middle of nowhere, face to face with a snorting reindeer charging straight at you. Of course, not all fieldwork days looked like that; mostly we were just surrounded by small Arctic plants, which are substantially less intimidating.

We were in Abisko (northern Sweden) to study snowbed communities. Seventy-five years ago, the botanist Olav Gjærevoll did plant surveys in snowbeds all across the area, and we wanted to compare his findings with the communities we find nowadays, considering the impact of climate change. On top of that, I am using satellite data to understand how the melt characteristics of each snowbed have changed over the last decades. This brings us to the methods! Nine satellite pixels of 10 × 10 m were chosen per snowbed, and within this area we randomly surveyed five plots of 0.5 × 0.5 m, documenting the species and their abundances.

So, what did a fieldwork day look like? It really depended on the day and the mountain. Three snowbeds were surveyed on Nuolja. We would take a ski lift to get higher up and then hike further to reach the right snowbed. There we would stand in the middle of the snowbed and throw four sticks to randomly select the placement of the plots. We worked with a great team, and each pair surveyed one plot, working together and sometimes struggling to identify the many tiny sprouts…

It was super cool: we were often so focused on these tiny plants that we forgot we were on a mountain with the best view in Sweden!

This was, however, not the case when it started pouring. We were wet through and through, with nowhere to go! Very much aware of our location…

One time we went to Laktatjakko and left the trail, leaving all hikers in the area behind. The coordinates led us to a beautiful place; I even got tears in my eyes to be there. A spot where, perhaps, since Olav Gjaerevoll no other hikers had been. A rare fieldwork day in the sun! The season had been mostly cloudy, so the sunshine felt like a nice surprise. While we were working, a reindeer ran toward us and we had no idea what it would do. But it was not charging at us; it was heading for the herd behind us. She got separated from her calf, and they reunited right before our eyes.

After collecting all the data, we made camp close by, eating pesto pasta and listening to fun stories. That was the most plant-diverse and memorable snowbed we visited.

Now, after two amazing months in Abisko, it’s time to analyse the data. It is difficult to understand how snowmelt patterns have changed under the influence of climate change, but I hope to find a correlation between the change in snowmelt timing and the communities we find per pixel. Even though it would be the worst-case scenario, we expect to find less species-rich communities at pixels where snowmelt has shifted over the last decade.

This research could serve as an extra argument that climate change negatively influences biodiversity, even in environments that seem less affected by rising global temperatures.

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The green revolution of our playgrounds

Posted on October 12, 2026 by lembrechtsjonas

A blogpost by 3D Lab team members Kyra and Olivia

What

A super cool project that is currently taking place in Zeeland is the Groene Revolutie (translating to Green revolution) organized by IVN Zeeland. The goal? To greenify all school yards within one school generation! 

Currently, many school yards are characterized by monotonous tiling with very little greenery. Not only does this create a rather uninspiring, non-imaginative location for kids to play and learn, but it also turns schoolyards into heat traps during summer, with little room to escape the heat. A striking example was shared by a teacher who saw kids seeking shelter from the heat underneath a ping pong table. A greener schoolyard creates a more interactive environment to learn from, as well as a place where kids can actually relax and play during summer. 

The Green Revolution, doing what it does best: bringing green AND fun to formerly grey playgrounds!

To measure the effects of this greening, we (Kyra and Olivia) visited multiple schools to conduct both microclimate and biodiversity monitoring. Depending on the stage of the school’s greening journey, we carried out either baseline measurements (before greening) or follow-up measurements (after greening). 

Sensors & biodiversity monitoring 

Microclimate sensors were installed at locations that would be greenified to see how temperature and moisture levels change. Sometimes a bit tricky, as you can’t exactly place a sensor in a tile! Kids also helped us find suitable spots for the sensors. At schools that had already been greenified, some sensors had gotten lost during the process. Therefore, we sometimes had to reinstall sensors at their original locations. 

We measured biodiversity using a grid, recording the different plant species and their coverage in different parts of the schoolyard. Even the youngest children, who did not take part in the lessons, where curious about what we were doing and came to look at the different plants in the grid. They were very eager to help us look for new spots they thought we should measure, including one area where they claimed to have found 100 plant species!\

From grey to green – the various shades of those playgrounds as seen through our monitoring project

Teaching 

Besides doing the monitoring, we also gave lessons to the kids, where we not only explained the topics we study but also did activities to bring the theory to life: installing sensors together, looking for soil life, or searching for plants in the schoolyard. An extra bonus of teaching is that it makes kids feel more involved in the science, for example by feeling responsible for keeping the sensors safe. We would love to highlight two of the lessons we gave. 

Plant biodiversity 

For children aged 9–10, we went on a mission to discover plant diversity in their own schoolyard.  

The children first investigated a potato plant growing in a small pot and discussed what plants need to thrive; sunlight, water, nutrients and enough space to grow. This sparked a conversation about how removing paving stones from schoolyards can create more space for plants and provide a valuable habitat for insects, in which some schools already succeeded as a result of the recent greening projects.  

Equipped with a map of the schoolyard and the ObsIdentify app, the children searched for as many different plant species as they could find, where they observed that even their schoolyard can have a large variety of plant species.  

Along the way, some children came across the anise hyssop (Agastache foeniculum and were especially excited to discover its unique smell of mint and liquorice. The Chinese fountain grass (Pennisetum alopecuroides) also sparked interest due to its Dutch name; Lampenpoetsergras, which literally translates to lamp cleaner grass, something they found very funny.  

Soil life 

For children aged 6-8 and 11-12 we went on the hunt for soil fauna to discover what species live in the soil of schoolyards. First, we brainstormed about different species living in the soil and the important work they do; breaking down organic matter, providing nutrients for plants and helping to keep the soil healthy. We also discussed microclimate and how local temperatures can vary across their schoolyard. We asked where they would look for shelter during a heatwave and how these locations often overlap with the places where soil life likes to hang out. After the heated-discussion (quite literally!), it was time to go outside and look for small creatures to put in their magnifying glass jar. 

To start off, the kids created a nice little living space for soil life in their jars, filling them with soil and leaves. Once the mini-environments were ready, the hunt could begin! Some started to dig and stomp the ground (mimicking the rain) to look for rain worms, while others decided to look underneath tiles and planters, finding, to their amazement, many centipedes and isopods. Ants, slugs, spiders, and shiny beetles were also collected. One kid even managed to catch a bee (although not officially part of the soil life). During the search for insects the children also discovered a larva of the harlequin ladybird, or multi-coloured Asian lady beetle (Harmonia axyridis). One child asked us whether it had come all the way from Asia for its holiday, which was a funny, and very smart question that led to a conversation about how species can spread to new places.

Another great moment was with a child who initially seemed a bit hesitant to touch the ground, only digging with a small twig because she saw soil as something dirty. After some encouragement to join the digging session with bare hands, showing how nice it actually feels and explaining that you can always wash your hands afterwards, it was lovely to see that by the end of the lesson, she had her hands completely covered in soil and was smiling (one second later, followed by a high five with equally soil-covered hands). It felt like a small victory in helping someone feel more connected to nature and see soil as something other than just “dirty”.

And an extra bonus: all the schools can access their own schoolyard’s microclimate and biodiversity data, allowing them to track changes over time and continue collecting more data! 

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Little resistance where we expected it

Posted on September 22, 2026 by lembrechtsjonas

Once you have gone through the effort of collecting a global database, you can start playing with it. And one of the most fun things to play with, I’d say, is general ecological theories – the kind that you would think hold everywhere, but that usually play out differently depending on where and how you test them. We’ve done a few of those with our MIREN plant survey database from along mountain roads, and here’s another important one, just published in the Journal of Vegetation Science (Buhaly et al. 2026).

This time, the theory on the chopping block is biotic resistance: the old and intuitive idea, going back to Elton in 1958, that a diverse, well-established native community should be harder for a newcomer to break into. More species already occupying the available niches, competing for light, water and space, should mean fewer open doors for a non-native plant trying to move in. It’s one of the most-cited explanations in invasion biology, but it rests on the assumption that competition is what dominates plant-plant interactions. And we’ve known for a while that this assumption gets shakier the harsher the environment gets: in stressful places, facilitation (plants actually helping each other, via shelter, warmth or moisture) tends to take over from competition. High-elevation, alpine environments are about as stressful as it gets. So does biotic resistance survive the trip up to the treeline and beyond?

The scenery of this paper – one of our Norwegian mountain roads

Testing an old idea

Together with the whole consortium, and led by Meike Buhaly, we used our MIREN road survey data to find out, using 15 mountain regions on six continents. At each site, a plot runs along the roadside, and a second one starts 50 m off the road and heads into the (semi-)natural vegetation behind it, the same paired design we’ve used since 2007, and that has featured oftentimes on this blog here. On top of that, we (well, mostly the lead author team in Germany, I just collected the leaves) built a proper trait dataset, with nearly 1,500 leaf samples, run through a near-infrared spectrometer back in the lab, to calculate not just how many native species a plot holds, but how functionally different those species actually are from one another.

Spelling out our expectations for this paper, based on conflicting theories: in Hypothesis 1 (H1), we expected that at low elevations, fewer non-native species would be found in communities with high native diversity due to competition. We hypothesized the opposite at high elevations (H2), with diverse native communities facilitating the establishment of non-native species. In Hypothesis 3 (H3), we anticipated a steeper slope of the relationship between non-native species richness and native diversity in natural habitats. Additionally, in Hypothesis 4 (H4), we hypothesized that the ratio of non-native species in natural versus disturbed roadside habitats would be higher in high-elevation environments than at low.

No resistance from richness – sometimes the opposite

The graph supporting the conclusions here. A bit counterintuitive: the y-axis shows the slope of the relationship between natives and non-natives. Positive values suggest more non-natives in species rich plots, which we unexpectedly see happening at low elevations (top panel). At high elevation, the relationship is neutral rather than positive.
For functional diversity (bottom panel), the pattern is very different

The short version: using native species richness as the classic proxy for biotic resistance, the expected resistance pattern didn’t show up anywhere in this dataset. If anything, it was reversed at low-to-mid elevations, where non-native richness was consistently higher with native richness. This was true, unexpectedly, both at the roadside and in the natural vegetation, plausibly because species-rich, structurally complex lowland communities simply offer more niches and microsites, for natives and non-natives alike, than their species-poor counterparts.

Looking at functional diversity told a different story, however. At low elevations, functionally diverse natural communities did host fewer non-natives – that’s one piece of actual biotic resistance we did find! But climb the elevation gradient, and that relationship weakens, then flips: at the highest elevations, functionally diverse native communities host more non-native species again. Exactly what you’d expect if facilitation, not competition, is running the show up there, as has been shown before for native cushion plants acting as “nurse plants” for exotic invaders in the high Andes.

So: some evidence for biotic resistance at low elevations, when using functional diversity, but overall a fairly strong case for the opposite to be happening.

Going back to Norway 2012

Then, at the end of the paper, there’s a part that I am a big fan of personally. Back in 2012, as a master’s student doing the first MIREN survey in northern Norway, I found that the ratio of non-native to native species in the roadside – compared to the untouched vegetation right behind it – increased steeply with elevation. My reading at the time: weaker resistance up high lets a disproportionate share of whatever non-natives do arrive spill off the road into the natural vegetation. That finding did get published, in my first ever peer-reviewed publication, but I always felt a bit hesitant. I trusted the pattern and process, but I felt like we just didn’t have enough data – very low invasion levels in Norway – to confidentially accept the claim as proven.

The global dataset now shows that this ratio does indeed climb toward high elevations, as we saw in Norway. However, it’s not a simple upward slope. It’s a U: the ratio of non-natives in natural vegetation relative to the roadside is highest at both ends of the elevation gradient (around 0.6 at each extreme), and dips in the middle. The high-elevation arm of that U is the one I stumbled onto in Norway — non-natives that make it up the road managing to spread into the surrounding alpine vegetation surprisingly easily, either helped along by exactly the facilitation signal described above, or by an overall reduction in interactions (my reading). The low-elevation arm is a different story, though: lowland sites are where most non-natives arrive in the first place, have had by far the longest time to build up a presence, and can draw on a far bigger regional species pool, so plenty of them eventually work their way off the road there too, just through sheer numbers and time, and regardless of the resistance levels.

The famous U-shaped graph of the ratio of non-native species in the natural vegetation versus the roadside

Which also explains, rather neatly, why my Norwegian roads never showed that low-elevation bump: Norway’s cold climate, isolation and modest regional species pool have always made it something of an outlier when it comes to that kind of long-term, low-elevation invasion build-up. What I picked up on in 2012 was thus really just one half of a much bigger, two-sided global pattern, and it took fourteen years and a lot of collaborating mountains to see the other half. Glad!

The native Angelica archangelica in a Norwegian roadside

Reference: Buhaly, M., Turner, S.C., Kreuz, N.K., Vandvik, V., Veltmann, B., Alexander, J.M., Lembrechts, J.J., et al. (2026). No signal of biotic resistance to non-native species establishment in high-elevation communities. Journal of Vegetation Science, 37, e70174. https://doi.org/10.1111/jvs.70174

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Proving extinction is hard. But we can do so now.

Posted on September 3, 2026 by lembrechtsjonas

For decades, climate change ecology has mostly been a story about shifts: species moving upslope, poleward, tracking the climate they’re adapted to as it slides out from under them. It’s one of the best-documented fingerprints of warming in nature.

What we’ve been much worse at showing is what happens at the far end of these shifts: actual extinction. Not “the range is contracting”, but the species being gone, locally, for good. That’s surprisingly hard to prove, and that for two good reasons. First, a single before-and-after comparison – the kind most historical resurvey studies rely on – have a hard time telling a real decline apart from population fluctuations or missed observations; you need repeated resurveys over time, at the same place, to separate signal from noise. Such standardized long-term surveys are rare. Second, alpine specialists are tough, long-lived plants that respond to a changing climate with a considerable lag, so a species can be quietly suffering in silence for decades before it actually disappears. So even though we’ve had every reason to expect that warming is pushing cold-adapted specialists off the top of mountains, actually catching that happening – at scale, and in relation to how much a place has warmed – has remained tricky.

In a new paper out this week in Science, driven by Johannes Wessely, Stefan Dullinger, and a long list of GLORIA colleagues, we finally got to prove what everyone already feared.

Where we looked for extinctions. The map shows the 16 mountain regions in our study, with circle size showing how much local extinction we found there – bigger circles, more species lost. On each of the 62 summits, researchers return to the same 16 permanent 1×1 m plots every seven years, arranged just below the peak (right), so we’re always comparing exactly the same patch of ground over time.

The reason that I – as an ecologists from the ‘lowlands’ – am so drawn to the mountains for my research, is that these mountains are close as we get to a clean experiment. The mountain summits we looked at here experience very little land-use change, no fertilization, none of the usual confounders that make biodiversity loss so hard to pin on any one cause. The GLORIA network has resurveyed the same 1×1 m plots on 62 summits across 16 European ranges every seven years since 2001, resulting in four surveys, 21 years of data from 896 permanent plots. If a species disappears from a mountaintop, warming is one of the few plausible suspects left.

High-elevation plants, like this Gentiana, are increasingly under pressure

Summit plant diversity has been rising for years, as lowland species colonize newly hospitable ground. We knew that, and that obviously remains true. But behind that increasing richness, local extinctions have been rising too. What’s more: these extinctions are getting faster with each survey, and this at every scale we checked: plots, summits, whole mountain ranges. Richness went up because colonization outpaced extinction, but that fact was hiding the losses. And what we are loosing, unfortunately, are exactly the cold-adapted specialists that make high mountains botanically unique.

Extinctions on the rise! Each dot is one mountain summit, showing what share of its species disappeared between one survey and the next. Color shows how much that summit had warmed till then – yellow is more warming, purple is less. Two things are important to note here: dots (and the trendline) clearly get higher over the three survey periods, and the warmest summits tend to sit toward the top.

Importantly, what predicted these extinctions was more than just time. Where the paper gets scarily elegant is where it shows that these extinctions truly correlate with how much a summit had actually warmed. Every extra 0.1°C over the preceding 14 years came with a measurable rise in extinction rate, and warming actually explained far more of the pattern than time alone. Species were also more likely to disappear from their warm, low-elevation range margin, and from communities shifting hardest toward warmth-loving species. Good to know, perhaps, as well: a preceding decline in cover was – while noisy – an early warning signal of extinction.

An extinction debt coming due?

Alpine specialists are tough, slow-growing, long-lived and thus often lagging behind the changing climate. That raises an uncomfortable possibility: what we’re seeing may be the first instalment of an “extinction debt” built up over decades of past warming. Now, that extinction debt is starting to be paid, which means that more losses could already be written in stone.

We’re not claiming climate change is the biggest driver of biodiversity loss everywhere; land-use change and nitrogen deposition still dwarf it in most human-dominated landscapes. But on summits, where those confounders barely exist, the fingerprint of warming on real local extinctions is now about as clear as it gets. And it’s growing. Measurably.

Reference: Wessely, J., et al. (2026). Rising plant extinction rates on European mountain summits. Science.

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