One fine afternoon last may, Jayne Belnap drove north out of Moab, Utah, in her beige Lexus SUV when the highway vanished. In an instant, a 100-foot-tall cloud of dust had swallowed up her vehicle. She wanted to brake, but she worried about another car slamming into her from behind. She tried to pull over, but she couldn’t see the shoulder. So Belnap split the difference: “I figured if I just crept slowly enough that I’d eventually get out of there or fall off the road.”
Luckily, the dust storm passed after a few minutes. But Belnap, who works at the U.S. Geological Survey and is the world’s foremost expert on the biological crusts that lock in desert dust, is well aware of the risks these tiny particles pose to people. In the 1990s a ranger at Canyonlands National Park in Moab, where she conducts fieldwork, broke her knee and two vertebrae in a collision caused by a dust storm. Dust affects denizens of the western U.S. in less dramatic ways as well. In the air, it can lead to respiratory problems, whereas dust settling on snowy mountaintops causes spring melts earlier in the season, harming agriculture in dry valleys.
Dust is poised to become an even bigger problem. Belnap has found that the total dust deposited in mountain lakes has increased sixfold since the early 1800s because of the livestock that stomp on and break the fragile crust. Today ever more off-road vehicles used for recreational fun and resource exploration comb through our deserts and tear up these top layers. Meanwhile the onslaught of climate change in the dry western states will reduce the formation of crusts and the growth of grasses, which also hold soil together.
Belnap, a laid-back former Olympic ski hopeful, recently spoke with Scientific American about her interest in desert crusts and how climate change and dust will affect the lives of Westerners. Excerpts follow.
Scientific American: What was your first introduction to the world of desert crust? Belnap: One day a professor I knew from college showed me these organisms growing on the ground. They were all these different lichens and mosses: pink and yellow and green. They were just gorgeous, and I said, “Wow, what is this stuff?!” And he said, “Well, ya know, I can tell you their names, but we don’t know anything at all about what they do.” That’s when I got really interested for the first time, but then I didn’t do anything about it. I kept goofing off.
Kept goofing off? Well, I was a hippie.
You were a hippie? What do you mean by that? Yeah! I hitchhiked from Alaska to Tierra del Fuego, I lived in a ski resort in Alta, Utah, for several years, and I surfed in Santa Cruz. I was a good, solid hippie. I didn’t do drugs, but I have wanderlust of the feet. I always had my plant book and my bird guide. So even though I didn’t have a formal education until many years later, I was always driven to know the system.
The system you decided to focus on was desert crust. Why is it so important? I realized that few other things fix nitrogen in the desert and stabilize soils. Nitrogen, as it occurs in the atmosphere, is not in a form usable by vascular plants or animals, so it has to be converted, and that can only be done by cyanobacteria and a few other bacteria. When people talk about “nitrogen-fixing plants,” they are not really talking about the plants, they are talking about the bacteria that live in nodules on the roots of the plants. In deserts, the soil is covered by cyanobacteria that occur free-living or that partner with fungi as lichens on the soil surface. The only other way to fix nitrogen is lightning, but we don’t have a lot of that in the desert. And because plants grow very far apart in deserts, there is not much holding the soil in place other than soil crusts.
How thick is the desert crust? It depends on the soil because these cyanobacteria have to photosynthesize to pull carbon dioxide out of the air and fix it as carbon for themselves. If you have a thick, heavy, clay soil where the light doesn’t get through, they’re going to be right at the surface. If you’ve got a nice sandy, fluffy soil where you’ve got a lot of quartz, then light can get down quite a ways—they’ll go down half a centimeter or even a centimeter.
How do cyanobacteria, whether free-living or in lichens, hold the sand together? They put out this sticky, gooey stuff made of polysaccharide starch. It holds water, so it allows them to dry more slowly. It also holds on to nutrients and keeps them from leeching out. Because it’s very, very sticky when it’s wet, these guys can cruise around the soil, and they leave this stuff behind that links the sand grains together.
What is the most significant cause of damage to these crusts? The human footprint! I mean that in the broad sense. The biggest problem is compressional disturbance, and that can be vehicles, it can be animals, it can be those seismic trucks exploring for oil. Or off-road vehicles, livestock, or people hiking or biking. The filaments between the sand grains are easily crushed when they’re dry. Nitrogen fixation needs to happen in an anaerobic environment, and when you break the crust up, you aerate it. They’re also photosynthetic, so they have to be on or near the surface, and if the soil gets churned and they get buried, then they die. Surface disturbances are expanding ever more as we look for energy supplies, and as we recreate more, and as the population increases and gets pushed into places where the soil crusts are needed to hold the dust down.
How long does it take them to recover from damage? They need rain to recover, but these are deserts, and rain doesn’t happen very often. For a cool, high desert like the Colorado Desert, getting that good, solid cyanobacterial crust that will resist wind and water erosion probably takes 10 to 15 years. For the lichens, you’re probably talking about 40 or 50 years. To climb down in the Mojave, where it’s really, really hot, then it’s in the hundreds of years to get the lichens back.
How does climate change affect that process? Less rainfall is going to mean less activity time for cyanobacteria and lichens, which means recovery will be slower, nitrogen fixation will be less and carbon fixation will be less. We have lichen species that appear to be at their physiological tolerance limits for temperature, and so we’ll probably be losing them and getting other ones coming up from the South that may or may not serve the same role as the ones we’re losing. In particular, we seem to be losing our biggest nitrogen fixer, the jelly lichen Collema. It’s gone from about 20 percent cover to about 5 percent cover in our long-term plots in national parks over the past 20 years, during which time we have had some very hot periods.
In what ways does the loss of crust feed back into the climate system? One of the biggest effects for regional weather patterns is the albedo of surfaces. By trampling on lichens and mosses, we’ve gone from a very dark surface to a very light surface over much of the western U.S., which means we have a surface that reflects more heat, which can lead to reduced cloud cover and rain. Dust in the atmosphere both reflects and absorbs heat and is also important in atmospheric processes.
There are huge implications for dust loading in the mountains. One of them is that when you have dust deposited on the snow, it darkens the snow and makes it melt a lot faster. As the snow melts from under the dust layers, the dust layers pile up on one another through the season, making the snow surface darker and darker. Earlier melting means water enters streams and rivers sooner than normal, leaving less late-season water. In 2009 we had a very dusty year, and we had a 48-day earlier snow melt because of dust. Our models show dust can annually decrease water in the Colorado River by 2 to 7 percent. So if you own a ski resort, you’re not going to be a very happy person; if you’re a water user in the valley, like a farmer, you’re also going to have big problems.
Have there been more dust storms out West in recent years? In Phoenix and Texas during the past couple of years, we have had these big, giant haboobs: dust storms that are literally 5,000 feet high. It seems that the answer is yes, but we’re also getting much better at observing and recording dust storms. We have had a series of very dry years, so it’s really hard to tell. Now we’ve got dust-monitoring stations, but there are only a few, and they’ve only been around since 2006.
Over a longer time scale, you have found that there’s been more dust in the air? That’s right. Dust cores extracted in mountain lakes show that the input of dust increased radically around 1850, when the large livestock herds hit the West. In one core, dust inputs went up from about 100 grams per meter squared per year to 800 grams per meter squared per year. Around 1900 we had a massive die-off of the livestock herds in the West, and in 1934 the government passed the Taylor Grazing Act to rein in overgrazing. The dust dropped to about 600 grams per meter squared per year. We don’t have enough resolution to see how energy exploration and off-road vehicles have affected it over the past 20 years, but inputs are holding steady at about 600 grams per meter squared per year.
Are native grasses also being affected by climate change? They are shallow-rooted, and with less water and hotter temperatures, they are not going to do well. In our long-term study plots, we have seen Indian ricegrass go from 40 percent cover down to about 4 percent during hot and dry years. They come back with wetness, but if it is dry year after year after year, then they are not going to. So overall, they are going down. This is the grass that is important for the base of the food chain, including mice and rabbits. It is also the most important grass for livestock in this region.
It sounds like ranchers will be facing a lot of changes. I truly do not believe ranching in the West is going to be economically viable in even as short as 20 years where I live. We’re going to have a vacuum in all these western lands, and if we don’t come up with something, there are lots of things that can fill this vacuum in ways many of us won’t like. Ranchettes and developments for rich people with jetports, antler hunters with ATVs driving everywhere and just a million different things could fill these voids in a way that is far more destructive than cattle ranching. So I really think we’ve got to think hard about what we’re going to do when ranching is no longer economically viable.
What types of actions could help rangelands? Several things. We could get much better at how we explore for oil and minerals. Right now we just have these trucks driving across soils, disrupting the surfaces. We do this over and over again because the information is proprietary, and so each company has to do its own exploration. We could certainly do much better at planning things such as solar and wind farms, including where they are placed and how we should share roads and power lines going to and from them. And we need to think about the effects of these actions on land albedo. Revegetating disturbed areas and abandoned croplands would help prevent dust storms.
We could be much better at how we deal with livestock grazing and recreation, where we think they should take place and at what time of year. We just need to start putting dust into the equation, and I think that dust credits are one option. Seriously. Ranchers could sell their grazing rights and receive money for keeping the dust down, just like industry can buy or sell carbon credits. As water supplies, especially the Colorado River, begin getting more and more scarce, people will be getting seriously creative about how to keep the dust down.
Luckily, the dust storm passed after a few minutes. But Belnap, who works at the U.S. Geological Survey and is the world’s foremost expert on the biological crusts that lock in desert dust, is well aware of the risks these tiny particles pose to people. In the 1990s a ranger at Canyonlands National Park in Moab, where she conducts fieldwork, broke her knee and two vertebrae in a collision caused by a dust storm. Dust affects denizens of the western U.S. in less dramatic ways as well. In the air, it can lead to respiratory problems, whereas dust settling on snowy mountaintops causes spring melts earlier in the season, harming agriculture in dry valleys.
Dust is poised to become an even bigger problem. Belnap has found that the total dust deposited in mountain lakes has increased sixfold since the early 1800s because of the livestock that stomp on and break the fragile crust. Today ever more off-road vehicles used for recreational fun and resource exploration comb through our deserts and tear up these top layers. Meanwhile the onslaught of climate change in the dry western states will reduce the formation of crusts and the growth of grasses, which also hold soil together.
Belnap, a laid-back former Olympic ski hopeful, recently spoke with Scientific American about her interest in desert crusts and how climate change and dust will affect the lives of Westerners. Excerpts follow.
Scientific American: What was your first introduction to the world of desert crust? Belnap: One day a professor I knew from college showed me these organisms growing on the ground. They were all these different lichens and mosses: pink and yellow and green. They were just gorgeous, and I said, “Wow, what is this stuff?!” And he said, “Well, ya know, I can tell you their names, but we don’t know anything at all about what they do.” That’s when I got really interested for the first time, but then I didn’t do anything about it. I kept goofing off.
Kept goofing off? Well, I was a hippie.
You were a hippie? What do you mean by that? Yeah! I hitchhiked from Alaska to Tierra del Fuego, I lived in a ski resort in Alta, Utah, for several years, and I surfed in Santa Cruz. I was a good, solid hippie. I didn’t do drugs, but I have wanderlust of the feet. I always had my plant book and my bird guide. So even though I didn’t have a formal education until many years later, I was always driven to know the system.
The system you decided to focus on was desert crust. Why is it so important? I realized that few other things fix nitrogen in the desert and stabilize soils. Nitrogen, as it occurs in the atmosphere, is not in a form usable by vascular plants or animals, so it has to be converted, and that can only be done by cyanobacteria and a few other bacteria. When people talk about “nitrogen-fixing plants,” they are not really talking about the plants, they are talking about the bacteria that live in nodules on the roots of the plants. In deserts, the soil is covered by cyanobacteria that occur free-living or that partner with fungi as lichens on the soil surface. The only other way to fix nitrogen is lightning, but we don’t have a lot of that in the desert. And because plants grow very far apart in deserts, there is not much holding the soil in place other than soil crusts.
How thick is the desert crust? It depends on the soil because these cyanobacteria have to photosynthesize to pull carbon dioxide out of the air and fix it as carbon for themselves. If you have a thick, heavy, clay soil where the light doesn’t get through, they’re going to be right at the surface. If you’ve got a nice sandy, fluffy soil where you’ve got a lot of quartz, then light can get down quite a ways—they’ll go down half a centimeter or even a centimeter.
How do cyanobacteria, whether free-living or in lichens, hold the sand together? They put out this sticky, gooey stuff made of polysaccharide starch. It holds water, so it allows them to dry more slowly. It also holds on to nutrients and keeps them from leeching out. Because it’s very, very sticky when it’s wet, these guys can cruise around the soil, and they leave this stuff behind that links the sand grains together.
What is the most significant cause of damage to these crusts? The human footprint! I mean that in the broad sense. The biggest problem is compressional disturbance, and that can be vehicles, it can be animals, it can be those seismic trucks exploring for oil. Or off-road vehicles, livestock, or people hiking or biking. The filaments between the sand grains are easily crushed when they’re dry. Nitrogen fixation needs to happen in an anaerobic environment, and when you break the crust up, you aerate it. They’re also photosynthetic, so they have to be on or near the surface, and if the soil gets churned and they get buried, then they die. Surface disturbances are expanding ever more as we look for energy supplies, and as we recreate more, and as the population increases and gets pushed into places where the soil crusts are needed to hold the dust down.
How long does it take them to recover from damage? They need rain to recover, but these are deserts, and rain doesn’t happen very often. For a cool, high desert like the Colorado Desert, getting that good, solid cyanobacterial crust that will resist wind and water erosion probably takes 10 to 15 years. For the lichens, you’re probably talking about 40 or 50 years. To climb down in the Mojave, where it’s really, really hot, then it’s in the hundreds of years to get the lichens back.
How does climate change affect that process? Less rainfall is going to mean less activity time for cyanobacteria and lichens, which means recovery will be slower, nitrogen fixation will be less and carbon fixation will be less. We have lichen species that appear to be at their physiological tolerance limits for temperature, and so we’ll probably be losing them and getting other ones coming up from the South that may or may not serve the same role as the ones we’re losing. In particular, we seem to be losing our biggest nitrogen fixer, the jelly lichen Collema. It’s gone from about 20 percent cover to about 5 percent cover in our long-term plots in national parks over the past 20 years, during which time we have had some very hot periods.
In what ways does the loss of crust feed back into the climate system? One of the biggest effects for regional weather patterns is the albedo of surfaces. By trampling on lichens and mosses, we’ve gone from a very dark surface to a very light surface over much of the western U.S., which means we have a surface that reflects more heat, which can lead to reduced cloud cover and rain. Dust in the atmosphere both reflects and absorbs heat and is also important in atmospheric processes.
There are huge implications for dust loading in the mountains. One of them is that when you have dust deposited on the snow, it darkens the snow and makes it melt a lot faster. As the snow melts from under the dust layers, the dust layers pile up on one another through the season, making the snow surface darker and darker. Earlier melting means water enters streams and rivers sooner than normal, leaving less late-season water. In 2009 we had a very dusty year, and we had a 48-day earlier snow melt because of dust. Our models show dust can annually decrease water in the Colorado River by 2 to 7 percent. So if you own a ski resort, you’re not going to be a very happy person; if you’re a water user in the valley, like a farmer, you’re also going to have big problems.
Have there been more dust storms out West in recent years? In Phoenix and Texas during the past couple of years, we have had these big, giant haboobs: dust storms that are literally 5,000 feet high. It seems that the answer is yes, but we’re also getting much better at observing and recording dust storms. We have had a series of very dry years, so it’s really hard to tell. Now we’ve got dust-monitoring stations, but there are only a few, and they’ve only been around since 2006.
Over a longer time scale, you have found that there’s been more dust in the air? That’s right. Dust cores extracted in mountain lakes show that the input of dust increased radically around 1850, when the large livestock herds hit the West. In one core, dust inputs went up from about 100 grams per meter squared per year to 800 grams per meter squared per year. Around 1900 we had a massive die-off of the livestock herds in the West, and in 1934 the government passed the Taylor Grazing Act to rein in overgrazing. The dust dropped to about 600 grams per meter squared per year. We don’t have enough resolution to see how energy exploration and off-road vehicles have affected it over the past 20 years, but inputs are holding steady at about 600 grams per meter squared per year.
Are native grasses also being affected by climate change? They are shallow-rooted, and with less water and hotter temperatures, they are not going to do well. In our long-term study plots, we have seen Indian ricegrass go from 40 percent cover down to about 4 percent during hot and dry years. They come back with wetness, but if it is dry year after year after year, then they are not going to. So overall, they are going down. This is the grass that is important for the base of the food chain, including mice and rabbits. It is also the most important grass for livestock in this region.
It sounds like ranchers will be facing a lot of changes. I truly do not believe ranching in the West is going to be economically viable in even as short as 20 years where I live. We’re going to have a vacuum in all these western lands, and if we don’t come up with something, there are lots of things that can fill this vacuum in ways many of us won’t like. Ranchettes and developments for rich people with jetports, antler hunters with ATVs driving everywhere and just a million different things could fill these voids in a way that is far more destructive than cattle ranching. So I really think we’ve got to think hard about what we’re going to do when ranching is no longer economically viable.
What types of actions could help rangelands? Several things. We could get much better at how we explore for oil and minerals. Right now we just have these trucks driving across soils, disrupting the surfaces. We do this over and over again because the information is proprietary, and so each company has to do its own exploration. We could certainly do much better at planning things such as solar and wind farms, including where they are placed and how we should share roads and power lines going to and from them. And we need to think about the effects of these actions on land albedo. Revegetating disturbed areas and abandoned croplands would help prevent dust storms.
We could be much better at how we deal with livestock grazing and recreation, where we think they should take place and at what time of year. We just need to start putting dust into the equation, and I think that dust credits are one option. Seriously. Ranchers could sell their grazing rights and receive money for keeping the dust down, just like industry can buy or sell carbon credits. As water supplies, especially the Colorado River, begin getting more and more scarce, people will be getting seriously creative about how to keep the dust down.
