Earth & Sky

The following person was interviewed for today’s program. Our thanks to:

William Bowman
Director of the University of Colorado Research Station
Faculty Member of the Department of Ecology and Evolutionary Biology
University of Colorado
Boulder, Colorado

Interview with Bill Bowman:

ES: Thanks for talking with Earth & Sky today, Dr. Bowman. I understand you’re in the field at the moment.

BB: That’s correct. I’m at the Mountain Research Station in Colorado. It’s the field station for the University of Colorado, at about 9,500 feet.

ES: You recently organized a symposium on diversity in mountain ecosystems at the Ecological Society of America meeting in Portland. Can you tell me some of the reasons and background into putting that together?

BB: The issue really came out of the Rio Accord in 1992, where it was recognized that mountain areas had particular value with regards to biodiversity. And, at that meeting they declared the year 2002 the International Year of the Mountain. There are a multitude of justifications for that.

Mountain areas tend to be hotspots of biodiversity. And that’s the result of topographic relief. It’s the result of many of those mountain areas being marginal, in terms of resources that can be extracted, at least economically. So, as a result, many of these mountain areas are fairly well protected. For example, in the United States, many of our mountain areas are wilderness areas, or National Parks. So, much of the endemic, native diversity is located in mountain areas. It’s also been recognized that although only 10% of the Earth’s population lives in mountain areas, probably greater than 50% of the world’s population is dependent on resources that come from mountain areas.

And that can include water. Water is a huge issue – it’s going to be the resource of the 21st century, in terms of the quantity of the water, and the quality of the water. And both of which are intimately related to issues of mountain biodiversity. So, there are also resources such as fiber, timber, and energy – either they’re derived from mountain ecosystems.

A reason that I’ve been particularly interested in mountain ecosystems and biodiversity issues is that, as I mentioned, many of these mountain areas have not really been economically developed. And so, they’re currently not being developed, so they make good indicator systems – the canary in the coalmine. We can measure changes, critical changes in both biological and chemical variables that give us hints about how mountain ecosystems are responding to what we would call indirect effects of humans on the global system.

So, for example, mountains serve as really good indicators for impacts of climate change. We can actually separate out the effects of resource extraction and climate change by looking at biological indicators, such as changes in the abundance or the composition of plants and animals and microbes.

And there are good examples of that already. In the Alps of Europe, they’ve documented very significant changes in the flora on the summits of mountains. And that’s actually been rolled into a global network called GLORIA. It’s a global network of observing the summits of flora in different mountain chains, and looking at how those change through time, and trying to use that as a detection of the biotic response to global change.

Other indications include responses to air pollution. In the western United States, we’re concerned with acid rain. Emissions standards in the western U.S. have not really kept pace with environmental concerns. We’re looking at changes in stream and lake chemistry, changes in the biological composition of those lakes, as sensitive indicators of acid rain. And in particular, nitrogen pollution in those ecosystems. I’ve personally been looking at that from the terrestrial side, looking at plant species composition, and we think that we’ve got pretty good indication that even in pristine wilderness areas, which are classified in terms of Class 1 in terms of the Clean Air Act. But there are changes that are occurring as a result of emissions from power plants, emissions from automobiles, from agricultural use, that are having changes on those ecosystems.

ES: Could you describe a little bit more what you mean by an “indirect impact” on the environment?

BB: Anything where there’s not a direct physical impact is something that I would call an indirect impact. Much of the hypothesis about what’s going to happen in mountain and other ecosystems, in response to things like climate change, are derived from modeling studies. People will look at what variables will make up the functioning of ecosystems, or what determines the plants or animals that are in a given place. And they’ll construct models that predict that, and then run those models to see what will happen to ecosystems in the future. That’s been one approach, and it’s certainly allowed us to develop hypothesis about how ecosystems will change. But there also have been some experiments done. For example, there have been direct warming experiments that have been going on at several different sites. The Rocky Mountain Biological Laboratory in Colorado has warming experiments going on now. It’s been going on for over ten years. So they’re directly looking at what impact warming of the air to the predicted value that we’re probably going to see in the next 50 years, what impact has that had on the plants and microbes in an ecosystem, and what impact do the changes have on the functioning of that ecosystem. Similarly, we’ve been doing experiments at the Niwot Ridge Site, here at the front range of Colorado, looking at what happens when you raise nitrogen impacts on the soil. We’re seeing elevated nitrogen inputs, as I mentioned, from human activities. So we’re looking at what thresholds of nitrogen input do we need to hit before we start to see significant changes in the chemistry of water, or significant changes in the plants or microbes that make up the soils. And then we’ve been using that information to predict how the system function will change. That’s the biodiversity function link. And, the results are intriguing. We’re actually finding results that suggest that the system might actually accelerate change, particularly here in the Colorado alpine, by pushing plant species composition towards species that actually do better under high nitrogen concentrations. That actually enhances the turnover of nitrogen in the soil by microbes, which can lead to greater nitrogen loss from the terrestrial system. So we’re concerned that there may be a positive feedback to nitrogen deposition, which can actually enhance the rate at which nitrogen is lost in the terrestrial, and into the aquatic ecosystems. One of the concerns that we have there is that with this increased nitrogen loss, we actually increase the acidity of those watersheds. We’ve been monitoring the chemistry of those watersheds for over 30 years now. In the 1990s, we began to see what’s called episodic acidification. We define that as the loss of acid neutralizing capacity in those lakes. So we’re seeing these periods of episodic acidification that seem to correspond quite well with the rate at which nitrogen is entering the system. So we’re concerned that thresholds of nitrogen emissions and of nitrogen inputs into the system that have been used for forested ecosystems just simply are not going to work for some of these high-altitude systems that we work with. We’re concerned that we’re going to see a fairly rapid loss of ecological integrity that could feed into potentially some rapid changes in the stream chemistry and stream biota.

ES: Could you describe a bit more for me what’s happening to nitrogen as it passes along at different stages in the environment?

BB: Nitrogen naturally occurs in the atmosphere in very large concentrations. The atmosphere is actually 80% nitrogen gas. But it’s in a chemical form that’s inert. That is, it simply cannot be used by biological organisms. Humans convert that dinitrogen gas into nitrogen oxides when they combust gasoline in their engines or in power plants under high temperature and pressure. That gets converted into these nitrogen oxides that then enter the atmosphere in a much more reactive form.

The same thing happens in agricultural systems. You can lose ammonia gas from agricultural systems, which, again, enters the atmosphere in what scientists call reactive forms. Those forms have a limited lifetime in the atmosphere before they’re lost into places, potentially very distant from where they’re emitted. And that’s been the case for the wilderness areas here in Colorado. We’re not exactly sure of the sources of that nitrogen, but probably half of it is derived from the industrial areas of the Denver-Boulder-Fort Collins-Colorado Springs metro areas. So, that’s the origin of the nitrogen. The relative inputs have increased on the order probably, maybe doubling of the nitrogen deposition of the last 10 or 15 years.

Some of that, interestingly, is related to an increase in precipitation as well. The more precipitation you get, the more that nitrogen gets washed out of the atmosphere. But there have been significant concentrations in those nitrogen species as well leading us to suggest that the rapid population growth that’s occurring here in Colorado is probably having a strong impact on the emissions and the subsequent loss of that nitrogen from the atmosphere.

Now we’re talking ranges of nitrogen input into the ecosystem that are significantly lower than other ecosystems. So as a result, scientists have not really given as much attention to the problems of nitrogen pollution into these western ecosystems. But in the last five years we’ve begun to realize that there is a much more significant problem there as we’ve begun to see these changes in stream chemistry, changes in the biological composition of lakes, and the terrestrial ecosystems.

One of the goals of our site is to maintain long-term records of the vegetation, of the animals, of the stream chemistry. And the National Science Foundation has established a network of these long-term ecological research sites. Part of the goal of those has been to be able to monitor changes and to be able to relate those to environmental change that may be occurring. We have vegetation records here that date back to the 1950s that we can use. So, a combination of actually monitoring these vegetation compositions in long-term plots, we coupled that with experiments that we do, where we manipulate the variables that are of interest, be that climate change, or nitrogen deposition, or potentially even increases in ultraviolet radiation, we can do experiments to see what will happen when we change a particular environmental variable. We then compare those results with the long-term changes in our plots to see if maybe we can compile evidence that suggests that the system is responding to a particular environmental stressor.

ES: Can you describe a little bit what these mountain ecosystems are like?

BB: One of the unique things about mountain ecosystems is that there are very strong gradients in the environment. As you go up in elevation, temperatures decrease, and precipitation increases, partial pressures of oxygen and carbon dioxide also decrease. And that has a very strong effect on the biological communities that you find. And that results in higher diversity in those ecosystems. In Colorado, the lower elevations consist primarily of open stands of ponderosa pine. As you increase in elevation, you run into more closed stands of pine and spruce and fir, and finally you get into the very high elevation ecosystems, where you get beyond the trees, above treeline, and into the alpine vegetation, which is sometimes called alpine tundra because of how much it resembles the arctic vegetation, which is called arctic tundra. So we use each of those communities in slightly different ways. Most of our experimental work has been done in the Alpines, above treeline, because that’s a vegetation community that really has not been impacted much by humans. The lower elevation systems have been used by logging, for mining. So there’s a bit of a legacy, a holdover, as it were, from human effects on those ecosystems in the 19th and early 20th century. Then, as you probably well know, those ecosystems have also been subjected to periodic fires. We’ve had some significant fires in Colorado over the last four years. So we like to use the high elevations for these climate change and atmospheric chemistry study because they really don’t have that holdover effect from earlier human use. And they also, as it turns out, tend to be more sensitive to some of those changes. Even though the plants that grow there tend to be quite long lived – some of the plants that I work with are as old as 70 or 100 years old, or maybe even older – you can have sensitive changes in the abundance of those species, which can occur over very short time periods. Another system that’s even better for that are the lake ecosystems, because the changes there are much more rapid. You can have changes in the phytoplankton or the algae that make up those ecosystems. Those can change quite rapidly. And there have been some very important studies done in lake ecosystems here in Colorado where they’ve cored the sediments at the bottom of the lake to get a sense of how have the phytoplankton or the algae changed through time, and how does that correspond to changes in chemistry of changes in climate. And some of those go back as much as 12,000 years. Of course, for some of these more modern studies, we’re interested in how those changes occurred in the past several decades. And one of my colleagues at Fort Collins, Jill Barrett, has been able to use those studies to tease out changes in the algae abundance in these lakes, and to relate that to this nitrogen pollution that we’re seeing.

ES:

BB: The effect locally is subtle but it’s very important. And it’s very important because of the chemical impacts that it could have. There’s several theories about what will happen as nitrogen inputs into ecosystems. Most people believe that once changes in the acidification in ecosystems occur, that those changes will be rapid, and potentially irreversible. Although there are data from central Europe that suggest that some of those changes can be reversible. So there is some hope there. Now this nitrogen pollution that we’re concerned about tends to be a regional problem, and yet it’s becoming globally a much more important problem, as countries begin to industrialize. The emissions of nitrogen oxides begin increases, and pollution like that should be on the increase as a result of industrialization.

There are more widespread concerns about climate change in mountain ecosystems, because it’s felt that there might be such a rapid changing climate, that ecosystems might not be able to change or move fast enough to keep pace with the relatively rapid change in climate that could occur. And there’s also concern that ecosystems at the highest elevations may simply just get squeezed out. I think some of those concerns are a little bit naive, in that there certainly is the potential for climate to change and impact ecosystems. But what we found from historical records from ecosystems is that they often change in unique ways. In other words, if you look at ecosystems 10,000 years ago, the composition of the plants and animals that make those communities up, they could be quite different because there were, at that period of time, unique combinations of climate and precipitation. And there is also a bit of a stochastic factor, a chance factor, in how those communities get assembled. We’re not necessarily going to see the same biological communities change in response to these global change-forcing factors. We could see unique communities assemble themselves. We could very well see significant losses of species as result of inabilities to change genetically, or just simply inability to move fast enough to keep pace with the rate of environmental change.

ES: Earlier you mentioned threshold levels of nitrogen input into streams – what’s on either side of that threshold?

BB: With any kind of environmental change, and I’ll use nitrogen inputs because it makes good example, as you begin to increase nitrogen inputs, or as you begin to increase temperature, a given community or ecosystem has the ability to resist change – it’s what we call ecosystem resilience – you get to a certain point where you begin to see significant changes. And that’s the threshold I’m talking about. How that’s defined has actually been codified in some European communities, where they’re a little more concerned about some of these nitrogen pollution problems. We have tended to think of thresholds in terms of changes of the chemical composition of streams. So where we begin to see changes in the concentration of nitrate, for example, during the growing season, once we observe an increase in what used to be nitrogen limited ecosystem to a nitrogen sensitive system, you would start to see elevated levels of nitrate – that would be the threshold that most land managers and ecologists would use. In our studies, we’ve actually been using biological indicators. So, for example, I’ve been looking for significant changes in the composition and the diversity of alpine ecosystems, and at what level we begin to see significant changes. I’ve also been following that up looking at levels of inorganic nitrogen in the soil, and at what level of nitrogen inputs do we no longer see complete uptake of that nitrogen during the growing season. So that’s the kind of thresholds that we’re looking at. It has a variety of different definitions. It tends to be defined primarily by physical factors such as stream chemistry, but one could certainly begin to use biological indicators in trying to determine what critical thresholds are.

ES: Could you talk a bit about one of the things you looked at in the ESA symposium – the role of biodiversity in these mountain ecosystems?

BB: Biodiversity is one of those terms that used a lot lately without a whole lot of precision. In our academic sense, biodiversity has at least three different levels. It could include genetic diversity within an organism and within the populations of that organism. The way we tend to use it is more ecological diversity, and we define that as simply the number of species, and how abundant those species are. There’s also a broader, spatial scale of diversity that’s called landscape biodiversity. And that’s the diversity of communities across the given landscape. That’s how species within those communities turn over as you go across that landscape. One of the main reasons why there’s been a lot more concern about biodiversity is that there’s a realization that we’re losing diversity relatively quickly. So we need to turn our attention to understand the consequences of the loss of that biodiversity. So this symposium was organized to try and begin to relate what we know about diversity in mountain ecosystems and to the functioning of those ecosystems. So we were trying to specifically relate it to things like water quality and water yield, to slope stabilization. There’s an idea that the more diverse a plant community is, the more diverse the rooting systems will be. That actually acts to serve as a better anchor to the soil. One of the obvious, unique things about mountain ecosystems is that they’re subjected to gravity – gravity pulls on the slopes, and they are, particularly on very steep areas, you can have significant slope erosion if you don’t have a diverse plant community there to tie the slopes down. And that would have very significant implications for the yield and the quality of the water. We’re also trying to make links for the biodiversity of mountain ecosystems and how much biomass gets produced by the plants there. There’s some good data to suggest that the more diverse an ecosystem is, the more diverse a community is, the more productive it is. There’s also a suggestion that some of these communities can be better filters for things like nitrogen pollution if they’re more diverse. And so that was really the focus of this symposium, to try to begin to link that diversity with the functioning of those ecosystems and to put that into the context of some of these environmental changes.

ES: And I’d guess that diversity has an effect on the quality of the water coming out of mountain areas?

BB: The quality of the water derived from these mountain ecosystems is derived from the integrity of the ecosystems there. The ability of the ecosystems to filter out some of these pollutants is important and related to the diversity of those ecosystems. Now, the main concern, really, is in the changes in the acidification of those waters, as well as changes in the biota within those waters. There’s the potential that municipalities will have to treat that water more if you begin to have algal blooms in the water. But, quite frankly, there’s an even larger problem with the loss of sewage from people’s septic systems as you go downhill. So the air pollution problem is really more related to some of these more pristine areas, particularly national parks, which could see problems with maintaining trout populations if those waters become so acidified that both the trout and the insects that they depend on can’t tolerate the levels of acidity and the levels of aluminum in the waters. The changes, when they occur, could be very rapid. It’s thought that once the capacity of the system is exceeded, to take out the pollutants and to take out the acidity of the water and the precipitation coming in, once that gets exceeded, things could change very rapidly. As I mentioned, that seems to occur in an episodic fashion here in the Rockies. We’re seeing that it occurs, and then it disappears for a while. But eventually, we may get to a point where it just simply is there and it stays there for a while. Now there’s hope that systems can, through mechanisms we don’t fully understand, can actually revert back to a nonacidified situation. We get hope from studies that have been done in Central Europe, or Eastern Europe, where acidification of many aquatic ecosystems occurs during the industrialization during the Soviet era, where there were really no environmental controls. And so many of those ecosystems lost much of their biota, much of their integrity. But now that some of the pollution controls are in effect, we’re seeing some of those ecosystems begin to return, and begin to return to healthy states. Of course that doesn’t mean that we want to allow our aquatic ecosystems in high mountains of the western U.S. get acidified to where we’re seeing significant biotic changes. We want to make sure that those changes don’t occur. So the real concern is primarily for the biological integrity of the high ecosystems, and to make sure that we’re not compromising those resources. In terms of the water resources themselves, most municipalities can deal with the levels of nitrogen that we’ll probably see come in. And in fact they already do because we get nitrogen loss from septic systems at low elevations. So they’re already coping with that.

ES:

BB: It wasn’t addressed specifically in our symposium, but it has been addressed by other researchers. I mentioned this group in Europe that’s looking at the changes in biodiversity in mountain ecosystems is at least an indicator of what’s going on. There are other groups in the Arctic and similar groups in the Alpine that are using a uniform that’s called the ITEX, the International Tundra Experiment to look to see what will happen to the biota as a result of warming. Now, one of the unique things about global warming is that it actually is a regional phenomenon. Some areas of the globe may not necessarily get warmer, and one of the climate change scenarios for the temperate mountain ecosystems is that they may actually see more significant changes in precipitation rather than temperature. So we’ve actually been manipulating precipitation rather than temperature to see what effects that’s going to have on the system. But that’s probably getting a little bit away from your question.

ES: So how are climate changes affecting things like snowfall in these mountain ecosystems?

BB: Our 50-year record of climate indicates that we’re actually seeing greater precipitation during the fall, which means longer snow cover of the system. And so that has a very significant result on the functioning of the ecosystem. Because there’s a lot more activity during the winter than we ever thought could happen. And that could actually be amplified by greater snow cover, which acts like a climate cushion, as it were, to help warm soils, to enhance biological activity during the winter. So we could see some very significant changes there. There are suggestions that climate change has impacted populations of mammals. In particular, there was a study in Great Basin mountain ranges found that the loss of populations of picas, and picas are basically small, modified rabbits that occur in very high-elevation ecosystems, some of these populations had disappeared over the last several years, and the implication there was that this was due to climate change, although the actual causal mechanisms weren’t as clear. There is concern that there could be the loss of some of these high-elevation species as a result of climate change, just simply because they can’t keep pace with the rate of climate change that could occur. And we’re not quite sure what are the implications of that.

As climate warms, the organisms that occur in a given area have to be able to adapt to new thermal regimes. In other words, they have to be able to maintain positive carbon gain. For animals, that means being able to eat enough. For plants, that means being able to photosynthesize enough. These organisms are already very well adapted to the climate conditions they occur in. And, as you warm up the climate, the rate of carbon loss can actually begin to exceed the rate at which carbon is gained. So species may die out simply because they can’t adjust physiologically. It’s not within their genetic ability to change. So, the rate of genetic change can’t simply keep pace with the rate at which climate is changing. The other option, of course, is for those organisms to move. And many of them reproduce vegetatively. That is, they produce a shoot, or an underground stem, or whatever, that allows them to move into an adjacent patch, if that patch is vacated. And that rate is simply not going to be able to keep pace with climate change. Really, only those species that can reproduce sexually, and reproduce seeds, that can be moved to more suitable locations, those are the species that are going to be able to survive any sort of rapid warming that could occur in mountain ecosystems.

ES: Thanks again for talking with me today. Is there something important that I missed in asking you about?

BB: I think one of the most important findings that came out of our symposium was how critically important the below ground responses are going to be. I mean this is a component that we just don’t know enough about. A lot of the biology in mountain ecosystems goes on below the soil surface. And we’re just learning an awful lot about the those processes, and quite frankly, we don’t even know the identity of those organisms that are doing this because we’re only, within the last five or ten years, developed the techniques that can be used to identify the microbes, including the fungi and the bacteria that are doing these critically important ecosystem processes. So, I think that our realization, that there is a lot of diversity there, that it changes very dynamically, was an important outcome of the meeting. And, I guess in the context of the environmental change that we’ve been talking about, there’s of course the hope that the microbial part of the ecosystem will be able to keep pace with environmental change. But in terms of the primary producers, the plants that produce most of the energy in the ecosystems, there’s concern about how they will be able to keep pace. And there’s also a strong concern about how they may actually exacerbate some of the problems that could occur. For example, there’s the situation of plants changing that actually accelerate the rate of change of soil chemistry, because of the chemical properties of those plants. That’s one thing that I mentioned earlier. Other findings were that a good system that we should begin to use to look at how at how environmental change, warming, or not necessarily chemical change, but really how climate warming could affect the development of some of these systems, looking at what happens as many of these glaciers recede, there were three groups of researchers who gave presentations at this symposium that talked about the development of these communities below ground. And this is really a unique thing. As I mentioned, people have looked more at the plants and animals, and very little at the soil biological community, and how important that is to the development of the system, and how it is able to respond to environmental changes, something that we’re just beginning to get a handle on.

ES:

BB: The alpine right now is a low resource environment. That is, it has a low supply of nitrogen. It’s made up primarily by species that have very low growth rates. They have low inherent growth rates. They just simply can’t respond to changes in resources very quickly. That includes sedges, that are grass-like species, and some herbaceous plants we call forbs. But there also are some examples of plants that do have the capacity to grow much more quickly when resources are made available. So, for example, when you have a wet year, there are plants such as grasses that could simply respond much quickly. Now, in the year-to-year variation that we see, there tends not to be a very large shift to say, from say these sedges, to the grasses. But if we begin to increase inputs of nitrogen into the system, or increases in temperature and water, we should see a gradual shift away from the slow growing species to the faster growing species, from the sedges to the grasses. And the characteristics of those plants are such that the way they influence the soil is very different. The grasses tend to accelerate the rate at which nutrients are produced from the organic matter in the soil, and the rate at which those resources can be lost from the terrestrial system and put into the aquatic ecosystem.

ES:

BB: So a shift away from these kind of slow growing plants to more rapid growing plants should actually increase the year-to-year noise that occurs in the forage for herbivores. So, for example, you can imagine that the current situation is that it kind of sustains a fairly steady population of herbivores. Although we see variations in herbivore populations that may be related to things other than the forage that’s available. But, you can imagine that as you have much more rapid changes in the plants that are available for forage, that’s going to have a very significant impact on the population changes in herbivores. And that could have consequences that we really don’t understand. It could increase the susceptibility of some of those mammal populations to very large changes in population, and potentially even to local population extinctions if we have a very bad year. There’s a suggestion that the drought that most of the western U.S. is in right now could extend for decades. And if that were to occur, in combination with something like nitrogen deposition, we could very significant trophic-level interactions among the microbes, the plants, and the herbivores that are dependent on those systems.

David Schindler studies pesticides and the long-term storage of some of these pesticides in high elevation glaciers and snow fields, and the relatively slow loss of those pesticides into alpine aquatic ecosystems. And what happens in some of those ecosystems is that the concentrations are amplified with each feeding level, or each trophic level, so that in these very, very pristine areas, although they’re not so pristine, but in these very remote areas, you actually find fish with toxic levels of pesticides as a result of this long-term transport. So as a result, there are environmental changes that have very long term impacts on mountain ecosystems that we don’t understand fully yet. There could be other hidden dangers out there.

He’s also looked at mercury level at some of these relatively remote areas in Canada. When you burn the forests, it turns out that the forests have held a lot of the mercury that’s been emitted from pollution. And that just washes into the water after a fire. And that results in, again, toxic levels of mercury in the tissues of fish.

ES: Would you mind going back a bit and explaining why, out of all the “cocktail” of polluting chemicals out there, you chose nitrogen as the one to study?

BB: I kind of glossed over that, I’m glad you asked. It’s clear that one of the most dramatic changes in global nutrient cycles has occurred for nitrogen. And there are several reasons for that. One of which I mentioned earlier was the fact that nitrogen is so abundant in the atmosphere. The changes in the reactive forms of nitrogen have been much greater than other chemical elements. The other reason why it’s so important is that it’s so important in the biology of systems. You know, farmers add nitrogen to their crops in order to get them to grow more. So you can think of nitrogen as a good thing. It can actually fertilize ecosystems. But, as we find out, too much of a good thing can be a bad thing. We can actually get detrimental environmental effects as a result of too much nitrogen coming into the system. So, in terms of percentage impact of human activities, the nitrogen cycle has been impacted probably more so than any other element, maybe with the exception of carbon, which is an important greenhouse gas in terms of CO2 and methane. But it’s that change in the nitrogen cycle that’s having the largest environmental impacts, globally, relative to other elements. And that’s why we’re putting so much emphasis on nitrogen.

ES: Is there anything else you’d like to share with the listeners of Earth and Sky?

BB: I don’t think so, except that we need to be aware in our environmental policies that each area is unique. We can’t have an environmental standard for eastern forest ecosystem that’s going to work for a western alpine ecosystem.

The Environmental Protection Agency uses standards that have regional significance. The eastern United States has received a lot of attention because of acid rain, and for a very good reason. Levels of acid rain were higher there. Likewise, southern California has different standards as a result of higher air pollution, higher ozone there. The same considerations have not been used for the intermountain west. And, until there’s a realization that there’s a potential, maybe even the realization that biological resources, that is the plants and animals that make up high elevation ecosystems, have been impacted in these class one wilderness areas, there is not going to be a change in air pollution standards. In other words, we need to consider the unique aspects of the different ecosystems in coming up with air standards. A western mountain ecosystem is going to behave very differently from an eastern mountain ecosystem in its ability to take up air pollution in order to filter it out from aquatic ecosystems and to keep; detrimental environmental impacts from occurring.

ES: It’s hard to imagine our pollution reaching a place as remote as a mountain

BB: You’ve hit the nail on the head. There are these systems that we think are immune from any sort of impact. But then, you know, even in the remotest part of Antarctica, you can find human signatures in terms of the chemistry.