Big, rocky canaries in the coalmine

Posted on August 14, 2026 by lembrechtsjonas

Mountain tops are big, rocky canaries in the coalmine that is our planet. Up there, above the last trees, change happens in real time and out in the open: plants, rock and climate, negotiating directly with each other. If you want to see the effects of a warming world with your own eyes, a summit is a very good place to start looking.

I’ve mentioned it many times on this blog: as the climate warms, species shift upward, chasing the cooler conditions they’re adapted to. It’s one of the most robust patterns in climate ecology. But (and by now you probably know that a “but” is never far away on this blog) the closer you look, the more complicated that story gets. A new paper I had the pleasure of contributing to, just out in Nature Ecology & Evolution, digs into exactly that mess, and the picture it paints is a lot more interesting than “it’s getting warmer, so warm-loving plants are winning.”

Austrian Alps close to Innsbruck

Waiting for the long game

Detecting a slow-moving process like vegetation change requires one thing science is often failing at nowadays: patience. You need standardized data, collected the same way, in the same places, for a long time, before subtle trends become statistically visible above all the noise of local weather patterns, disturbance and plain old stochasticity.

We got there now, finally. One of the best examples of such datasets out there is GLORIA-Europe, arguably the largest coordinated monitoring network for climate-change effects, focussing on mountain summit vegetation. Since 2001, GLORIA teams have been resurveying permanent vegetation plots on summits right across Europe (and far beyond, but let’s stick to Europe for this story). In this study we used four such surveys, spanning 21 years, across 724 permanent plots on 53 summits in 14 mountain regions, from the Pyrenees to the Carpathians. On top of the vegetation data, many of these summits also carry soil temperature loggers, giving us a second, independent, on-the-ground record of how conditions have actually changed where the plants are actually growingm not just what a weather station kilometres away says. And don’t we all know how crucial I think that is!

Chasing the warmth-lovers

With that data in hand, the question we wanted to answer was as simple as it was genius: are these summit plant communities becoming dominated by more warmth-loving species – a process called thermophilization – and if so, does that track the pace of warming? It’s the kind of question that feels almost too obvious to need testing, right? Warmer summit, more room for species that like it warm. Case closed?

Strong, significant warming trend in both micro- (left) and macroclimate on and around European mountain tops

Ok, yes, thermophilization is happening, clearly and widely. Averaged across all 724 plots, the composition of summit communities has been shifting steadily towards warmth-associated species for two decades, a signal so consistent that nearly two-thirds of individual plots show the trend individually. It’s a slow process, but it is unmistakably there. And yes, both the interpolated macroclimate and the on-site soil microclimate warmed too, across almost every temperature metric we looked at. Cool findings on its own: climate change is happening, and species are responding to it. Louder now for the people in the back!

On average, summit vegetation is showing signs of warming (63% of plots show thermophilisation)

Ah, but did we now forget about the but I mentioned! That but is there in how loosely those two very real trends are actually coupled. At the level of an individual plot, the relationship between the pace of local warming and the pace of thermophilization was surprisingly weak. A single temperature metric, measured over the monitoring period, barely explained any of the variation in how fast a plots’ vegetation was showing signs of warming. Things improved a bit once we allowed vegetation to lag a few years behind temperature (four years turned out to be the sweet spot) and once we combined several temperature metrics instead of relying on just one. But even our best-performing models explained less than 10% of the plot-to-plot variation in thermophilization. Somewhat to our surprise, this held even more strongly for the on-site microclimate data than for the macroclimate – exactly the opposite of what we expected going in, given how often microclimate turns out to be the better predictor in this kind of work.

It’s not (just) the climate, it’s the neighbourhood

If temperature alone can’t explain why some plots thermophilize fast and others barely move, what does? This is where the story gets its real weight. We added two simple pieces of local context to the models: 1) how many warmth-loving species were already growing just below the top, ready to move in, and how much of the top was bare rock and scree rather than colonizable ground. Including these parameters helped the explanatory power jump substantially, to an average of 37% . And warming and colonizer availability interacted: where warmth-loving neighbours were close at hand, rising temperatures translated into thermophilization much more readily than where they weren’t.

In hindsight, that makes a lot of ecological sense. A plant community can only respond to warming with the species that are actually available to respond with. No matter how fast a summit warms, if there’s no thermophilic species sitting just downslope ready to move up, and no open substrate for it to land on, that summit simply cannot thermophilize quickly – climate change or not. Dispersal and substrate act as a kind of gatekeeper on the door that temperature is trying to open.

Thermophilisation rate interacts with the availability of thermophilic colonisers (low vs. high on the x-axis) just below the summit

What this means

None of this undermines the reality of climate-driven vegetation change on Europe’s summits, of course! The thermophilization signal is real, and it lines up with a genuine warming trend. But it’s a strong reminder that even the most simple stories in ecology hold complex and important nuances in them. The abiotic and biotic context a community sits in – its neighbours, its substrate, its dispersal opportunities – shapes how, whether, and how fast that response actually plays out. If we want to forecast how mountain biodiversity will look in fifty years, temperature trends alone won’t get us there; we’ll need to understand colonization dynamics and landscape context just as well.

Swedish Alps close to Davos

It also makes a strong case for keeping – and intensifying – long-term, standardized monitoring efforts like GLORIA. It took two decades of consistent data collection across an entire continent to even be able to ask this question properly, let alone answer it with any nuance. That’s a lot of ecologists and botanists standing on a whole lot of mountain tops over the year! Let’s make sure that we can all keep doing that.

Student taking a high-resolution GPS-coordinate of a snowbed plot surveyed for the first time back in the 1950s, in northern Sweden. Exactly the kind of science we should keep making possible

Reference: Hausharter et al. (2026). Widespread thermophilization but weak link to climate warming in Europe’s summit plant communities. Nature Ecology & Evolution. https://doi.org/10.1038/s41559-026-03150-x

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MEB 2026

Posted on June 2, 2026 by lembrechtsjonas

Big week in Montpellier this week, as the world’s microclimate ecology and biogeography community has gathered for the third global MEB conference.

After the first edition in Antwerp in 2022 and the second in Helsinki in 2024, this year’s conference is bigger and more diverse than ever.

Just one day in, I already feel like our field has truly grown beyond its original boundaries (symbolized, perhaps, by this brave little vine from the first day’s excursion). Microclimate has permeated nearly every corner of ecology and biogeography, and its importance for improving our understanding of ecological patterns and processes is high on everyone’s agenda.

That doesn’t mean the work is done – far from it. We also recognize that the world of microclimate is remarkably heterogeneous (something beautifully reflected in the landscape of the Cirque de Navacelles, visited during yesterday’s excursion).

In many ways, by incorporating microclimate into our research, we’ve added an entirely new dimension to ecology. The challenge now is figuring out how to embrace that complexity without becoming overwhelmed by it.

Fortunately, with a room full of bright and enthusiastic minds, we’re well equipped to keep moving the field forward.

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A beautiful birthday

Posted on May 24, 2026 by lembrechtsjonas

The MIREN network has turned twenty! Imagine: a global ecological network, built on friendship, enthusiasm, and a shared love for mountains, that has managed not only to survive, but to grow and thrive for two decades. In a scientific world often shaped by short funding cycles and shifting priorities, that is no small achievement.

And this truly is a year of celebration for the network. At the end of last year, we gathered in Innsbruck, Austria, for a workshop that looked both backward and forward: reflecting on where MIREN came from, while laying the foundations for where it is heading next. We also officially kicked off preparations for a new coordinated round of global mountain roadside monitoring in 2027. And now, to top it all off, a celebratory paper has just been published in Biological Invasions.

The paper tells the story of twenty years of MIREN: what the network has achieved, how it managed to sustain itself over such a long period, and what other global research collaborations might learn from it.

MIREN was founded in 2005 through the vision and leadership of Peter Edwards and Hansjörg Dietz in Switzerland, together with Catherine Parks and Richard Mack in the United States. They invited a group of ecologists to a foundational workshop on the outskirts of Vienna, where MIREN’s central aim first took shape: understanding and addressing the growing risks posed by biological invasions in mountain ecosystems.

Since then, the network has steadily expanded. Our core and longest-running initiative, the MIREN road survey, now includes data from 27 mountain regions across the globe, with 30 regions already planning to participate in the upcoming 2027 resurvey.

Map of the 27 contributing mountain regions to the MIREN road survey
Cumulative number of sites contributing to the MIREN road survey

One of MIREN’s greatest strengths, at least to me, is its decentralized structure. Every region has its own ecological story to tell – and many collaborators do exactly that through regional studies and local publications. But together, these regions also allow us to answer the much larger questions that no single mountain system could address on its own. That balance between local ownership and global collaboration is rare, and incredibly powerful.

MIREN is also unusually balanced in terms of global representation. In our core road survey, nearly half of the contributing regions (48%) are based in the Global South, and the steering committee is similarly distributed across continents. Of course, important gaps remain: tropical mountains and large parts of Africa – apart from South Africa – are still underrepresented. But compared to many international ecological networks, MIREN has managed to build something remarkably global.

That global nature does come with practical consequences, of course. Steering committee meetings regularly happen either before anyone’s first reasonable cup of coffee or well past midnight. Yet those sleepy faces keep showing up, year after year. And I think that says the most about the affection people feel for this network.

MIREN meeting in Innsbruck last year and doing what we did best: scale the mountains

One of the key questions we discussed during our recent meeting in Innsbruck was how to remain relevant in a rapidly changing world – scientifically, socially, and in terms of conservation priorities. We certainly do not have a definitive answer. But a few important ingredients became very clear.

One is maintaining a healthy balance between long-standing and new members. New voices bring fresh ideas, energy, and perspectives. At the same time, the continuity provided by members who have been involved for years helps preserve the values and practices that allowed the network to flourish in the first place.

Another crucial element is the importance of meeting in person. Those moments together allow us to periodically rethink our objectives, create space for new conceptual directions, and recalibrate priorities – while still keeping MIREN’s core mission at the center: standardized, long-term ecological monitoring.

And perhaps most reassuring of all was the level of enthusiasm in Innsbruck. Many regions are stepping up their efforts, launching exciting new local and global research projects, and expanding collaborations. Beyond the original road survey, we have also made major progress with MIREN Trails and MIREN Rocks, elevating both initiatives to the same level of standardized monitoring as our “classic” roadside surveys.

Trends in the main keywords in the 99 MIREN papers over time

Twenty years of MIREN have resulted in a remarkable scientific legacy: ninety-nine papers so far – with this latest one becoming number one hundred.

So yes – there is truly a lot to celebrate.

And the nice thing is: the story is far from finished. You can still become part of it yourself. Join the MIREN road survey in 2027, participate in the MIREN trail survey in 2028, or contribute to MIREN Rocks whenever you feel like it.

Because after twenty years, the mountains are still full of stories waiting to be told.

Reference: Pauchard et al. (2026) Collaborating across mountains: contributions of the Mountain Invasion Research Network (MIREN) to ecology and conservation. Biological Invasions

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500 species

Posted on May 13, 2026 by lembrechtsjonas

Last week, I spent a few days just outside of Barcelona for a PhD defence. Perfect timing, I thought, to finally cross the magical boundary of 500 unique species on iNaturalist. I had been hovering just below it for a while, and to me, that number always felt like the line between a casual observer and a slightly more committed enthusiast.

The magic boundary of 500 species on iNaturalist so easily crossed

Now, oh boy, was that easy.

Just a small walk – about an hour – from the train station to the campus, and the boundary was crossed, and then some: 45 new species added to my list. Of course, finding new species is always easier when visiting a new place. But there was something else going on too. The landscape was just that little bit… messy.

Agriculture, but messy – a landscape with room for a lot of biodiversity hidden in the verges, forest edges, shrubberies and the fields themselves.

A kind of messiness that has become unfortunately rare in the Netherlands, yet is so important for biodiversity.

It was farmland, but farmland filled with corners, slopes, edges, shrubs, trees, and tiny neglected patches where wildflowers could persist. The borders between “field” and “nature” were blurry. And those blurry borders were full of life.

That kind of landscape heterogeneity is harder to find in the Netherlands nowadays. Partly because we simply lack the topographic variation of places like Barcelona, where a gradient from a dry hilltop to a wet valley can create many different habitats within a short distance. But also because our landscapes have become increasingly optimized and tidy over time. Fields are cleaner, straighter, and more intensively managed. The small irregularities that once created space for biodiversity have often disappeared.

In the fields outside of Barcelona, it was often unclear where the field ended and the border begun, and plants loved that vagueness!

And when bits of semi-natural vegetation do remain, they are frequently affected by excess nitrogen deposition. Many of these places become dominated by a few highly competitive species – brambles, nettles, coarse grasses – leaving less room for the wide variety of plants that once characterized them.

Walking there made me realize how much I miss that ecological messiness in the Netherlands. Because these messy landscapes create opportunities for iNaturalist enthusiasts trying to reach arbitrary milestones, of course, but more importantly: because they create opportunity for plants, insects, birds and nature to thrive.

Until then, I suppose I’ll keep boosting my species list elsewhere.

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Mountain road microclimate

Posted on April 28, 2026 by lembrechtsjonas

This is a massively important paper. At least for me.

It brings together the work I’ve been doing in the Mountain Invasion Research Network and the Microclimate Ecology & Biogeography Network. And it finally answers one of the key research questions I was left with at the end of my PhD, back in the good old days of 2018.

During my PhD, I studied plant species distributions along mountain roads. That gradually pulled me into the world of microclimate, which seemed to be one of the core mechanisms shaping where mountain plant species can and cannot occur. One of my hypotheses – supported by experimental data from my PhD – was that roadsides create warmer microclimates, potentially allowing lowland plant species to move higher into the mountains.

A reasonable hypothesis, of course, and one we brought up in many papers since. But we still had to test it.So we started installing sensors along mountain roadsides across the network. But somewhere along the way, I got distracted. I started wondering: why limit ourselves to mountain roadsides? Microclimate is crucial everywhere. That eventually led to building SoilTemp, and later the MEB network.

Mountain roadsides are on average substantially warmer than the adjacent vegetation (here: Norway)

Yet the roadside sensors stayed there, and the data accumulated.

Eventually, we retrieved the data and slowly started making sense of it. I worked on it on the side for quite a while, until others joined in and really helped push it forward (Renee and Eduardo – thank you!). And now, after all those years, the results are finally published.

And boy, are they worth it! We observed on average a 1°C shift in mean annual temperature in roadsides as compared with the adjacent vegetation 50 m away from the road. That – and that’s quite mind-boggling – corresponds to more than 200 m of elevational displacement of the temperature regime (as we found a 0.45 degree Celsius elevational lapse rate). That means that plants could find similar average temperatures 200 m higher on the mountain in these roadsides – likely quite helpful with the observed upward movements of both non-native and native species.

Elevational trends in roadside (red) and adjacent vegetation (turquoise) temperatures across all studied regions.

While we observed significant variation in these trends between regions, we especially found strong evidence for warmer annual maxima and summer mean soil temperatures along roadsides compared to the adjacent vegetation, and lower annual minima and mean winter soil temperatures on roadsides at high elevations. Overall, the results suggest that roadside microclimates are much more tightly coupled to macroclimatic fluctuations than nearby natural vegetation. In contrast, intact vegetation appears to buffer temperature extremes, making those systems less directly exposed to broader climatic variation.

Another interesting pattern emerged in winter. Temperature differences between roadsides and adjacent vegetation likely reflect differences in snow cover and snow depth. Roads are often cleared of snow, while adjacent vegetation can accumulate deeper snowpacks through wind redistribution or ploughing. At higher elevations, where snow persists longer, those differences may become especially important.

So after years of assumptions, hypotheses, and scattered observations, the numbers are finally there: mountain roadsides substantially alter microclimatic conditions, often creating much more extreme thermal environments than the surrounding vegetation. Now comes the next step: testing whether those altered microclimates are indeed driving changes in species distributions.

Reference: Lejeune, R., E.Fuentes-Lillo, & Lembrechts, J.J. (2026). Mountain Roads Across the Globe Significantly Alter Local Soil Thermal Microclimates. Global Ecology and Biogeography 35, no. 4: e70237.

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The living farm

Posted on April 21, 2026 by lembrechtsjonas

Last week, we properly kicked off the fieldwork season. Under a bright April sun, we made our way to ‘De Boeije’ – a cosy, somewhat hidden farm right on our own campus at Utrecht Science Park.

‘De Boeije’ and its golden seas of dandelions on a sunny April day

I’m not sure how many of the thousands of people passing through the campus know about this little gem, but it’s well worth a lunchtime walk to the southwest corner on a sunny day.

This time, though, we were there for more than just a walk. We’re monitoring biodiversity as part of our global Ecological Fractal Network. Across the site, we sample vegetation in 1 × 1 m plots at multiple spatial scales to understand how biodiversity is distributed – and, crucially, how it can be maximized across those scales.

Vegetation monitoring. This field harvested around eight plant species per square meter

This hidden farm is one of the project’s flagship sites. Here, we are not just observing change, we are actively helping to shape it. De Boeije has been made into a Living Lab as part of Utrecht University’s Pathways to Sustainability. Within this Living Lab, we’ll collaborate with a wide range of stakeholders – from farmers and neighbours to schools and scientists – to experiment with more biodiverse and sustainable forms of agriculture.

Funny thing: we were already monitoring biodiversity here, and that monitoring has now neatly turned into the monitoring of baseline conditions, before these changes will take place. As the photos show, the farm is already relatively low-intensity, but we expect (and hope) to see further substantial improvements in the coming years.

And when those changes happen, we’ll be there to quantify them!

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