Goodbye!

Two big achievements yesterday: two of our master students defended their thesis, and will thus be able to put an endmark behind their education! A big congratulation to both Ilias Janssens and Bram Vanheule for all they achieved.

Ilias

Virtual trial thesis defence by Ilias Janssens, discussing his cool results on patterns in plant community traits in the Scandinavian mountains

Ilias studied the relative importance of climate and disturbance as driver of plant community traits, using a huge dataset of plant traits from over 160 species from the Scandinavian mountains. Main result: local disturbances like roads and trails have surprisingly small effects on community traits in comparison with large-scale drivers such as temperature.

Capture

Trial defence by Bram, exploring the role of urban heat islands on plant invasions

Bram had a much different arena to work in: Western European cities. His question: how do non-native plant species perform during a heatwave along a gradient from city to rural zones. The conclusion? Urban Heat Island effects are much less important than we anticipated; it is at the smallest scale (e.g. amount of soil available around the plants) that stress-levels are defined.

We hope to bring you more details on these fascinating topics soon, but for now wish the students all the best in their upcoming careers.

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10.000

Cartogramf

Cartogram showing the number of sensors in the SoilTemp-database. Countries colored and inflated based on the number of sensors.

We reached a milestone today: our SoilTemp database now hosts more than 10.000 sensors[1]! To celebrate this achievement – and the great news that our call for data in Global Change Biology is now published in its final format – I wanted to use our previous research to convince you why it is important to bother with this humongous task to compile a multi-thousand sensor database[2].

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Figure 2: In our seed-addition experiment on north- versus south-facing mountain slopes, invader biomass increased significantly in warmer plots (expressed as Growing Degree Days, the sum of daily mean temperatures from days above 0 °C). Data from Lembrechts et al. 2017.

 

It all started during my PhD-work on high-latitude invasions in the northern Scandes and the southernmost tip of the Andes. We quickly realized that performance of our studied non-native plants related significantly to the local soil temperature – more than to the macroclimate gradient (Fig. 2).

 

 

It is during these experiments that we realized the issue at hand: this soil climate we measured seemed critical for studies on organisms living close to – or in – the soil, yet we lacked good high-resolution gridded maps to scale up our measurements.

Further prodding in the cold and snow-rich mountain range of the northern Scandes, confirmed our hypothesis: modelling the distribution of small plants works significantly better using soil than air temperature (Fig. 3).

Graphical abstract

Figure 3: summary of the results from Lembrechts et al. (2019).

We knew the importance of microclimate for ecology was gaining interest everywhere, however, and reviewed the great studies showing that microclimate can improve species distribution models. This review however emphasized the gap: we didn’t have high resolution microclimate data over a large spatial extent (Fig. 4)!

That is when plans started to materialize, and we set to work to fill that gap in our available data: the idea for SoilTemp was born. We started gathering the brightest minds in microclimate research, and brought together all their painstakingly collected regional microclimate datasets.

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Figure 4: Workflow describing how in-situ microclimate measurements (as in the SoilTemp-database) can help calibrate and validate existing mechanistic models of present and future microclimate. Figure from Lembrechts and Lenoir (2020).

In the meantime, the potential for mechanistic microclimate modelling increased rapidly, a.o. thanks to the work from Ilya Maclean and Mike Kearney (Fig. 4). This created even more need for a global database, which would allow for large-scale calibration and validation of these models. Importantly, our ongoing efforts to build such a database are just the first steps: we’ll need long-term microclimate time series, and match them up with time series of biodiversity change and known physiological relationships (see Lembrechts, 2020).

Figure 1Even more importantly: we need to predict future microclimate, and how it is shaped by the interaction with changes in land use and biodiversity itself (see figure on the right). This is fundamental to allow accurate predictions of the fate of biodiversity in the future.

 

Now look again at the cartogram above. There is some crucial work to do to improve the global coverage[3], but we are working on it. We have been shipping loggers to many of the empty holes in the map, and countless enthusiastic researchers from all over the world keep reaching out to us with more data.

 

We will keep doing this, and invite you all to stay tuned and, even better, join this quest for better climate data for use in ecology! Next up: usable global soil climate products so our ecological models can finally get the true microclimate data they deserve.

 

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Microclimate logger in the Swedish mountains. Picture: Jan Clavel

Footnotes

[1] And many more still await processing in the coming weeks!

[2] Thanks Jonathan Lenoir for promoting these fascinating maps!

[3] And I truly believe filling this gaps is critical, both to get broad representation of all the Earth’s biomes, but also of a broad range of scientists from across all continents

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#togetherforbiodiversity

Biodiversity is essential for our survival and well-being. It nourishes and heals us. It provides us with oxygen and pure water. Biodiversity takes care of us, but it is in danger. Change and action are urgently needed to protect life on Earth, including ours. However, we can all do our bit to protect our biodiversity, which is why we now joint forces with numerous Belgian nature associations, universities and knowledge centres. Visit https://samenvoorbiodiversiteit.be/nl to learn all about the campaign. And above all: find simple individual or joint actions and tips to contribute to the conservation of our biodiversity. Every action counts, as it’s the sum of them all that will make all the difference.

Red de biodiversiteit, samen en nu'; coalitie van 39 natuur- en ...

More at: https://samenvoorbiodiversiteit.be/nl/ (in Dutch or French). Act with us!

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Early drought

Europe is suffering from extremely early spring drought. And again, as every year, our water use is back on the agenda. And it should be: water availability might become one of our society’s biggest problems. In fact, it already is: a Flemish municipality already had no water coming out of the tap at all, with even the firefighters getting in trouble to put out fires.

An extreme case, but it should serve as a warning: here in Flanders the water management is still focussed on the idea that the region is getting TOO MUCH rain. Let me tell you, if it ever was true, it is not anymore. We should stop managing our land to get rainwater removed as fast as possible. And, importantly, we should get rid of this attitude that water is an endless resource, and react surprised when we run out of it. Drought is our future, and we should all adapt our mindsets to this.

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Our cities are concrete jungles where rain water is supposed to run off into the drainage system as fast as possible. Here: a non-native Buddleja next to the A12 highway, Flanders

The impact of this dry weather can be seen clearly in the trial of our drought- and heat citizen science project, running in my garden (see figure).

Drought

The current drought spell is already drying out lawns since early April, with only two little showers and one rain spell to reduce the losses. The problem is that it is still so early in the summer season and already soil moisture levels dropped extremely low. As you can see by the rainy days beginning of May, we will need more than a week of continuous raining to get the lawn water back on track. While soil moisture in the cool and shadowy spot under the shrubs (blue line) was holding on till early May, the flushing leaves of the shrubs now brings down the moisture even faster. Plants are needing all the water they can get, and not much is coming in to compensate.

And there is no salvation on the horizon: there seems to be another ten days of little rain on the way, draining the lawns even more. You might want to brace for dry lawns in summer. Don’t worry about those, though, lawns are resilient and very often grow back!

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Uncertainty surrounding the prediction of microclimate change

We need to gear up the search for correct climate predictions to tackle the biodiversity crisis. In a recent perspective piece in the journal Science, we argue that our climate predictions do not take into account local changes in land use. Tackling this problem will require our new SoilTemp climate database and the joint collaboration of scientists from all over the globe. 

 Artificial temperatures

Weather stations serve well to monitor our daily weather and the changes in our climate. However, such data are much less relevant for nature. What is even worse: the predicted warming of our nature itself could also be very different from what the climate models predict.

The problem is simple: Weather stations measure the temperature at 1.5 to 2 meters above the ground, in well-ventilated rooms, above a neatly mown lawn. However, this is a very artificial situation, resulting in temperatures quite distinct from those that nature itself experience. Most animals and plants (insects, soil organisms, herbs, small mammals…) indeed spend a large part of their lives much closer to the ground, where temperatures can vary from a few to even dozens of degrees from that weather station temperature. You can experience this so-called ‘microclimate’ yourself when you put your hand on the hot beach sand on a summer day, or on a cool bed of moss in the forest.

Picture microclimate stations

Mini weather stations – like here in a lawn – give ecologists the climate where it matters for the ecosystem.

Faster warming

These big differences that we feel on the beach and in the forest over the years accumulate into a long-term climate that is on average several degrees warmer or cooler respectively than what a weather station indicates. We argue this week in Science that these differences are already crucial to understanding nature in the present, but that climate change is making them all the more crucial. A predicted increase in temperature of 2 °C could feel completely different on the forest floor, especially if mankind interferes. For example, another study in the same edition of Science, led by Florian Zellweger, reports that the climate on the forest floor in forests with more intensive logging has warmed up much faster than average in recent decades, with major consequences for the future of forest biodiversity.

Ecologists have been aware of this problem for a while, but no good solution had been found yet. Until now. Researchers from all over the world – we already united scientists from more than 50 countries – are joining forces to finally obtain climate data that can also be used to tackle the biodiversity crisis. We did set up ‘SoilTemp’, a database of climate data that is relevant for nature itself. By using temperature measurements there where it matters, we can gain insight into how strongly that microclimate can deviate from the measurements in the weather station in ecosystems across the globe. In doing so, we hope to answer the ultimate question: how large is the impact of climate change on our biodiversity?

Publications

  1. Lembrechts and I. Nijs, Microclimate change in a dynamic world. Science, (2020).
  2. Zellweger et al., Forest microclimate dynamics drive plant responses to warming. Science, (2020).
  3. Lembrechts et al., SoilTemp: call for data for a global database of near-surface temperatures. Global change biology, (2020).
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Trial in the village

Our citizen science project on garden microclimates (see this post) is slowly taking up speed. For now, it is trials-trials-trials, making sure all the gaps and holes are filled and all the questions are answered, before we launch the full 5000-logger strong program next summer.

While the first trials started simply in my own garden, we now had a nice little expansion: our neighbours were intrigued by the funny little mushroom in our front yard, and said they would love to have one too. Why not, I thought, the global pandemic is keeping all my loggers locked indoors for now anyway! So out we went: we mobilised the street’s WhatsApp group, and brought mushrooms and instructions to everybodies doorsteps. Now the neighbourhood is filled with garden daggers in a first example of what this citizen science project can do!

Garden loggers

Our little white mushrooms spread across our own garden, and the whole ‘Saliestraat’ street. 

This first ‘microcosm’ of the citizen science project we want to roll out across the whole of Flanders already thought us a lot: cats and dogs like playing with the little top hats of our mushrooms, for example, and lawn mowers are no friends of the bottom shield. People do find them very intriguing, though, and happily welcome the intruder in their lawns. And robust as they are, all of them did survive for now.

And then there is the data, of course, which is of course the best part! Just imagine this graph below rolling in from 5000 gardens across the region, telling us everything one wants to know about what’s driving our garden microclimates, and if and how can improve this ourselves, to make them a better place for humans and nature.

Example

Example of heat (at the soil surface) and drought measurements in my own garden, revealing an extraordinary dry and warm spring. 

For now, we’ll leave it at this first impression. We’ll leave detailed analyses of all the cool insights that are in their for later, when our project truly takes off!

 

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