How climate change is affecting our forests

When a severe summer drought hit Europe in 2018, the impact on food systems was immediate.

Poland’s corn crop declined by 20%. Germany’s total grain production dropped 16%. Romania’s oilseed production decreased 10%.

Four years later, climate change’s impact on ecosystems has become so profound that wet locations, such as forests, are acting more like dry systems, such as deserts.

Heather Throop, an associate professor in Arizona State University’s School of Space and Exploration, co-authored a piece in the journal Nature Ecology and Evolution on the changing ecosystems, why it’s critical to understand the processes that occur in deserts and what the long-term implications might be.

ASU News spoke to Throop about the paper.

Editor's note: The following interview has been edited for length and clarity.

Question: Let’s start with the 30,000-foot question. How is climate change effecting wet ecosystems?

Answer: So, where it’s been most pronounced is where there have been heat waves or very extended droughts. We have an example in Europe from 2018 where lots of corn fields and irrigated agriculture died. There was decreased plant growth in those systems, which leads to more exposure of bare soil on the surface that’s not covered by plants.

Q: So one of the impacts in these wet ecosystems could be food shortages?

A: Yes. It certainly changes how we would want to manage systems. So for food or for grazing animals, things like that, there’s our understanding of how these systems work, but it’s going to be different if we experience these different mechanisms that we haven’t typically thought of as important for wet systems.

Q: What are those mechanisms?

A: It’s basically the way that processes happen. Things like the patterns of availability of water, the processes that affect the cycling of carbon and nutrients through systems. So in the paper we present these 12 different dryland mechanisms that are really routine processes but aren’t commonly found in wet systems. And then we categorized them in the paper based on how likely these are going to happen in wetter systems in the future. What sort of changes would be required for us to start seeing those in wetter systems?

Q: How widespread is the change in our wet ecosystems? Or is this something we’re going to see develop in the next five to 20 years, say?

A: It’s certainly something that we see in some places. It’s been really variable. A lot of it is these extreme events, these high temperatures, heat waves and droughts. And climate change predictions would say that we will see more of that. They will also be more extended in nature in the future.

Q: What will happen to these ecosystems if climate change isn’t properly addressed in the next couple of decades?

A: Part of it is we need to approach this as a more complicated problem than just what it’s going to be like when it gets hotter. We need to understand that it’s not just that plants are going to be a little bit stressed for water and grow more slowly. We need to think about how do these systems work under different climate conditions, and where those climate conditions are the norm, what information can we use to shift our thinking? One of the challenges is that we, as scientists, tend to map these patterns. We use mathematical models to say how the system will behave under wetter conditions or hotter conditions, or something like that. But right now, what our models don’t really take into account is what if the rules by which the system works are different?

Q: Could we potentially see the loss of rainforest?

A: Certainly, I would say there are major threats to systems like rainforests from climate change in the future just because those systems will be operating under these different mechanisms. It will certainly change the behavior of these systems, and largely in ways that we don’t know right now.

Q: What behavioral changes could occur?

A: We have a lot of processes where carbon and nutrients are moved around and organic material is decomposed. Typically in wet systems, that’s driven by biological processes, by microorganisms that consume that organic material. In dry systems, we have a lot more influence of UV, of sunlight and high temperatures breaking down material that’s sitting on the surface. So instead of having biology driving that breakdown, we have physical processes driving it. One of the big differences with dry systems is that because you have limited vegetation, there’s a lot of open space, and you have a lot of redistribution, things blowing around on the soil surface. Where in wet systems, those things are staying in place, and you have a much more even distribution of resources.

Q: What’s the impact to wet systems if the distribution changes?

A: If the vegetation becomes more patchy because of drying, then the resources in the soil and all of the biological processes will become more patchy, which is very characteristic of dry systems. And that can affect food production.

Q: What can be done to ward off these changes?

A: That’s the billion-dollar question. Certainly, doing what we can to mitigate the impact of climate change just to reduce the temperature change and rainfall changes. But we also have to understand what is likely to happen, and that will help us in terms of thinking about management and being able to anticipate and then, at least in localized, small locations, try to mitigate the impact by understanding how some of these processes might be different. Unfortunately, we don’t have a good solution.

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