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Indiana University Professor Awarded NASA Grant to Study Drylands

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When you think of drylands, what first comes to mind? A field of zebras galloping across the savannas of Africa. Or, perhaps, a rattlesnake slithering past cacti in the deserts of Arizona. Maybe you think of a herd of cattle, munching their way through the Great Plains of the United States.

Dryland ecosystems make up around 40% of the land in the United States, including the vast desert of the Southwest and the Great Plains. Similarly, drylands comprise 40% of the entire Earth’s land surface. With this in mind, a better understanding of such a vast area of the globe proves necessary.

The world’s drylands and subtypes. Prepared using spatial data. (Courtesy of the Food and Agriculture Organization of the United Nations)

Indiana University professor Natasha MacBean shares a similar sentiment. She was recently awarded a grant from the NASA Research Opportunities in Space and Earth Sciences Carbon Cycle Science program to do just that, to understand more about drylands and specifically their role in the carbon cycle and how climate change could affect the ecosystem. Last week, Professor MacBean spoke with WFHB news about her work.

“My research into dry lands is primarily to understand the kind of ecosystem scale processes, that is the interaction between vegetation and water and carbon cycling and how that is responding to climate change and to land management change as well. Mostly that’s driven or motivated by a wider research theme of mine which is to understand global carbon cycling. We are obviously emitting carbon dioxide into the atmosphere and the land and the ocean are taking up, their absorbing about 50 percent of those emissions so we know that kind of global scale number but what we don’t know is really which ecosystems, which regions, and which processes are driving that, sort of what we call a sink of carbon. We also don’t know if we’re going to sort of maintain that 50 percent reduction on our emissions into the future or not. So we need to understand that better and it has been highlighted in the past decade or so that semi-arid ecosystems, even in dryland ecosystems more broadly, are playing a big role in that sort of year to year variability in global carbon cycling and so we want to understand that a bit better. There are lots of people working in the field in dryland ecosystems and understanding processes and that work has been going on for a while but where my research comes in is really scaling that up to broader scales, sort of regional to continental scales and then up to the globe as well and then for the second component of that is making sure that our process of understanding of the carbon, water, and vegetation dynamics is implemented into the kinds of global Earth system models that we are using for climate change projections for the I. P. C. C. for example.”

With this broad overview of Professor MacBean’s work in mind, the expert shared more about drylands themselves and some of their characteristics.

“Dry lands are inherently water limited. Most of the ecosystem processes are driven by moisture availability. So that means that there’s less rainfall on average and there is a potential for evaporation and evapotranspiration. There are lots of different strategies in these ecosystems, a lot of different vegetation types. There are strategies for dealing with that kind of seasonal water stress and year to year changes in water availability. Drylands cover about 40% of our land surface, some of that is the desert. So that takes up about 7%. So I think, 1/3 of the land surfaces are the semi arid, sub humid, dry land ecosystems that have quite a bit of vegetation and include savannas or grasslands, etc. And they have a lot of ecosystem services. They support about just over a third of the world’s population. So they have tons of ecosystem services for that population such as often these regions are used for grazing for livestock production. There’s obviously water availability issues and in those ecosystems for the populations that need water. We actually, in the US, I can’t remember now the number but we grow a lot of our crops in the US in the southwest and West, where it’s actually water limited, which I don’t think always makes that much sense. Especially for some of the crops that need a lot of water and therefore irrigated a lot. So these are the kinds of ecosystem services that come from these ecosystems. They’re also really diverse and they’ve got a lot of different flora and fauna that are often beneficial for foods, culture and medicines, etc. There are lots of different purposes and supporting a lot of the world’s population.”

Dryland ecosystems are extremely complex and important for many key species that depend on them as well as humans who depend on them for their livelihood and survival. A key part of MacBean’s research is to understand how climate change, and other human effects, could impact the drylands.

“Climate change, I’d say, is one of the big pressures, other pressures include population increase, and land management, you know, like I just mentioned are we really managing the land well, and these ecosystems, so often we are over grazing them, and over cultivating them and maybe not growing the right crops, etc. That’s one thing. And climate change interacts with that. The biggest thing that climate change is going to do in these ecosystems is change the water availability. And so that includes a couple of things. One is changing rainfall variability, so sometimes that means more intense storms. For example, the Southwest US is driven by the North American monsoon, which provides water availability, and that’s not necessarily going to go away, but the characteristics of it might change. If they’re more intense storms, then that’s not necessarily a good thing, we might lose a lot of that water as runoff. It’s just too intense for ecosystems to manage. But with climate change a lot of drought, most of the west and southwest of the US, for example, have been in a mega drought for most of the century. We think that can be exacerbated with climate change. So these ecosystems really rely on water availability, they’re adapted to the kind of seasonal changes in water availability. And as that changes, potentially more extreme droughts in the future climate change, the plants, and all the ecosystem processes are going to have to adapt to that. And the second thing I’d say with climate change that I think we’re seeing a lot now is potentially increased risk of wildfire. There is an interplay there with land management, and building, and sort of urban expansion and how we’ve managed fires in the past. But we think that, you know, one of the reasons why wildfires might be increasing is increasing temperatures and, again, dry land ecosystems, well adapted to deal with fire over, you know, 1000s, 10s of 1000s, 100s of 1000s of years. But, as these changes are sort of accelerating, the vegetation will have to adapt to that as well.”

Many farmers worldwide depend on drylands to provide areas for livestock. Seen here is a farmer with his herd of goats. (Courtesy of Dr. Mahfouz Abu Zanat & the International Union for Conservation of Nature)

Dryland ecosystems and how they relate to global carbon cycle and global climate is a topic that requires more understanding. As mentioned before, Professor MacBean was recently awarded a $900,000 dollar grant from NASA to provide funding for more research into drylands. MacBean described how this grant came about and what her team’s research will do to improve the mapping of drylands and better understand the potential environmental effects on the environment.

“So NASA has a bunch of different calls on different topics. And they have a carbon cycle science program, it’s specifically about understanding the carbon cycle of terrestrial ecosystems. It can be any type of ecosystem. And so, I’d been already doing research in dryland carbon cycling, and through my work and when I was at the University of Arizona and my collaborators there. So I got together with a few different collaborators who were working in the southwest, and working on dry lands, to put in a grant that was aimed at really improving our understanding of carbon cycling in dry land. And, and what we’re trying to do is a mixture of different things. So we’re trying to improve our mapping of different plant types, vegetation types, and soil cover in these regions, because they’re often very spatially heterogeneous. If you think of savannas, you know, you’ve got shrubs dotted everywhere, and it’s very difficult to map those types of ecosystems. And then once we hopefully can do that a little bit better, we’re going to take a lot of other measurements in the field, remote sensing measurements, and link the plant cover type to the function and their responses to changing rainfall, etc. And then the third part is to implement that into a model. So it’s really a kind of bringing together people working on different things, modeling, remote sensing, field measurement, working across scales, you know, scaling up from understanding ecosystem processes at the field scale to modeling at the regional to global scale, with remote sensing and satellite data. You know, that’s how it came about, just a meeting of collaborators who wanted to continue working on that.”

With an uncertain future, MacBean’s research offers a chance for scientists to understand and perhaps predict the future of drylands through the use of modeling. MacBean provided insight as to how this project will help in this endeavor.

“What we really want to do, and that’s, you know, one of the goals of this project is to make sure that we have the sort of right process, understanding in the kinds of models that we use to make (future) predictions like that. And then hopefully, by the end of this project, we wouldn’t have developed everything that we need in the model to look at those kinds of questions, but I think we’ll be able to run future simulations under climate change scenarios, and see whether we are seeing, for example, like an expansion of dry on vegetation, but that’s a real overall goal, but I’d say we want to really test and develop the models a little bit better, but before we say that more definitively”

With hard work and dedication, Professor Natasha MacBean’s work is being recognized for its immense importance and is now funded by NASA. With research just beginning, there are limitless amounts of information to still be learned about our world’s drylands.

*Interview was edited for brevity and clarity.

By Nathaniel Weinzapfel

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