Pushed out of the comfort zone
What is this?
Due to climate change, plant communities in Spain are experiencing dry conditions that they have never experienced before leading to defoliation and plant death. We need to understand how climate shifts affect plants and make tools to predict how affected will plant communities be under future climates.
Why does this matter?
- Because finding out how climate shifts affect plant species helps us predict how will our communities change and its impact on our society.
- Because making tools to predict plant community health at large scales without having to take field measurements saves us money and time.
How did you study this?
In 2013, an extreme drought hit the North East of Spain and many plants from the area started losing their leaves in response to stress. We measured the percentage of canopy that remained intact in 4000 plants from 20 different species and recorded the rarity of each species across the area.
Then, we compiled data of the distribution of each species across all Europe as well as their climate records for the last 50 years. We used these two big data sets to build computer models that could predict what climate conditions each species liked and disliked. Once we knew what kind of climate each species liked, we looked at how ''ugly'' it got relative to their preferences during the drought of 2013. Finally, we checked whether species with less foliage were the ones that experienced the least comfortable climate and whether the most affected ones were also the rarest across the landscape.
So what did you find?
Well... the first thing that we saw was that the drought changed the climate of the area and made it really bad!! Check it yourself in the picture on the right. These are computer models for three of our species. Cold colors represent areas where the climate is really bad for that species and warm colors are places where the climate matches the needs of the plants. The white square is the area where our plants live. As you can see, the place went from being pretty nice to being the last place where you would like to hang out! And this was the case for all the species we studied.
The second thing that we found was that indeed the species with less foliage were the ones that experienced the worst climate. However, what was really interesting was that the level of defoliation didn't directly depend on how bad the conditions were during the drought or how good they had historically been. The species that lost most leaves were the ones for which the climate had changed the most! To put an example, a species that experienced a climate that was ten times worse than before lost more leaves than a species that experienced a climate two times worse than what it used to be. As you can see below, the degree to which the species lost leaves depended on how much worse it had become. It was too uncomfortable for them to live there anymore.
What this suggests is that plants are adapted to the climate that they and their ancestors have always experienced and that any deviation from that climate puts them at risk of death.
If you remember, we also thought that the most affected ones would also be the rarest across the landscape. That's because we thought that the rare species would be the weakest ones; the ones less prepared to tolerate the already dry conditions of the area. Here we had a big surprise. Turns out that the rare species were the ones that lost less leaves!!
We didn't find out the exact reason that could explain this. However, we suspect that this is the result of natural selection. If these rare species are actually the weakest ones, it could be that only the individuals that have the best genes to tolerate drought are the ones surviving every summer and reproducing. Through time, this process can remove all the weak plants and leave only the ones able to tolerate the dry summers of the area (I like to call those super-plants). Of course big powers also come with big weaknesses... You can't keep your leaves nice and healthy during harsh droughts and reproduce a lot; because you have to put most of your resources into keeping your leaves alive instead of making seeds. Therefore, your population can't grow much and you remain a rare species across the area. This is a really cool hypothesis that someone can now test with our plants!
And the big point is...?
We have been able to predict how much a species would defoliate using our climatic models. This is really cool!! This means that we can use these models to predict the health of plant our communities under climate change. And we don't even need to move our asses out from the office to do so! That is a lot of money and time saved. It also helps us predict how our plant communities might change in the future. This is very important because plant communities provide many services that are critical to us. They prevent erosion and make oxygen, they are also the food for farm animals and provide habitats for the wildlife that we like to see when we go on a hike between many others. For this and many more, it is worth taking care of them and keep track of their evolution.
Hopefully, this study will help on that!
The actual paper for the nerds: