Nathan Stephenson's career as a research ecologist spans more than 25 years. Since receiving his doctorate in plant ecology at Cornell University, where his dissertation analyzed effects of climate on distribution of vegetation types, he has been working in the southern Sierra Nevada. For years he has studied the interaction of fire with forests, especially with giant sequoias, and he helped to refine a management regime using fire. Since the early 1990s, when he helped establish (and later became director of) the U.S. Geological Survey's Sierra Nevada Global Change Research Program, he has studied issues surrounding climatic and other global environmental changes in Sierra Nevada ecosystems.

Recently Stephenson has been speaking at conferences and other professional gatherings about ecological restoration in an era of rapid global changes. He contends that, although it's useful and necessary to be able to refer back to a historical baseline to see how a particular ecosystem worked, it's often no longer possible--or useful--to attempt to restore systems to a supposedly pristine "natural" state, one assumed to have existed at a particular historical point in time. What is important, he says, is to try to maintain native biodiversity and build an ecosystem's resilience rather than dictate its structure or species composition.

Coast & Ocean spoke with Stephenson by phone at the USGS's Sequoia and Kings Canyon Field Station in Three Rivers, California.

How did you arrive at your views about ecosystem restoration in this time of rapid global change?

Nathan Stephenson: I started my career as a scientist with the National Park Service; now I work for the U.S. Geological Survey, but I work in the same location I always did and on the same topics. I had a deep belief in the mission of the National Park Service, which is to restore and maintain naturally functioning ecosystems. It seemed pretty clear that to succeed at that in the Sierra Nevada national parks, fire needed to be reintroduced. Sequoia-Kings Canyon had been nationally known for having one of the most sophisticated and successful prescribed fire programs in the national park system.

Then in the early to mid-1990s, a couple of people here started to put together the numbers and look at how close we were to restoring the pre-European settlement fire regime, and we were falling pretty substantially short of that in spite of our best efforts. There's always something that, for good reason, gets in the way, whether it's being able to burn at the safest time of the year, or the air quality is too poor--which is a really big issue. You need permission from the Air Pollution Control District, and if you can't get that, you don't burn. Sometimes it's staffing, sometimes it's money--all these things come together to mean that we burn a lot less than used to burn before the arrival of European settlers. Safety is also a big issue.

And that created a crisis for me. I thought, it looks like no matter how hard we try, we're not going to meet the mission of the National Park Service in the strictest sense, of trying to restore the fire regime that used to be there. That little personal crisis started leading me to question everything. At the time I was studying the potential effects of climatic change, and I started putting all the pieces together and realizing that even if we could completely restore the pre-European settlement fire regime, all these other things are happening that have no precedent.

We have a lot of ozone air pollution that comes into the park, and it particularly affects a few species of pines, and who knows what else it might affect. We're getting more nitrogen deposition from the atmosphere than we did in the past, from fossil fuel combustion. We have invasive species: If I look out my window here in the foothills, probably 90 percent of the species are introduced from different parts of the world. We have a non-native fungus that was introduced a long time ago, the white-pine blister rust, and that's slowly but surely killing off the sugar pines in the park. And then you throw rapid climatic change on top of all that, which, if the models are correct, is going to become a bigger and bigger issue in the very near future. I just reached this crisis point where I said, my gosh, we can't go back to a "natural" past, it's just too late for that. And then I started to ask, well, what the heck do you do?

A point I try to bring home to people is that, for good reason, we have a tendency to look to the past, to try to find an analog to current conditions. That provides a comfort factor where, if we can figure out what our ecosystem looked like 500 years ago and restore it to look like that, we ought to be okay. But the environments we have today have no analog in the past, and so we don't have that extra comfort zone anymore of being able to look to the past and say, here's my model for what I want my ecosystem to look like.

Nathan Stephenson's career as a research ecologist spans more than 25 years. Since receiving his doctorate in plant ecology at Cornell University, where his dissertation analyzed effects of climate on distribution of vegetation types, he has been working in the southern Sierra Nevada. For years he has studied the interaction of fire with forests, especially with giant sequoias, and he helped to refine a management regime using fire. Since the early 1990s, when he helped establish (and later became director of) the U.S. Geological Survey's Sierra Nevada Global Change Research Program, he has studied issues surrounding climatic and other global environmental changes in Sierra Nevada ecosystems.

Recently Stephenson has been speaking at conferences and other professional gatherings about ecological restoration in an era of rapid global changes. He contends that, although it's useful and necessary to be able to refer back to a historical baseline to see how a particular ecosystem worked, it's often no longer possible--or useful--to attempt to restore systems to a supposedly pristine "natural" state, one assumed to have existed at a particular historical point in time. What is important, he says, is to try to maintain native biodiversity and build an ecosystem's resilience rather than dictate its structure or species composition.

Coast & Ocean spoke with Stephenson by phone at the USGS's Sequoia and Kings Canyon Field Station in Three Rivers, California.

How did you arrive at your views about ecosystem restoration in this time of rapid global change?

Nathan Stephenson: I started my career as a scientist with the National Park Service; now I work for the U.S. Geological Survey, but I work in the same location I always did and on the same topics. I had a deep belief in the mission of the National Park Service, which is to restore and maintain naturally functioning ecosystems. It seemed pretty clear that to succeed at that in the Sierra Nevada national parks, fire needed to be reintroduced. Sequoia-Kings Canyon had been nationally known for having one of the most sophisticated and successful prescribed fire programs in the national park system.

Then in the early to mid-1990s, a couple of people here started to put together the numbers and look at how close we were to restoring the pre-European settlement fire regime, and we were falling pretty substantially short of that in spite of our best efforts. There's always something that, for good reason, gets in the way, whether it's being able to burn at the safest time of the year, or the air quality is too poor--which is a really big issue. You need permission from the Air Pollution Control District, and if you can't get that, you don't burn. Sometimes it's staffing, sometimes it's money--all these things come together to mean that we burn a lot less than used to burn before the arrival of European settlers. Safety is also a big issue.

And that created a crisis for me. I thought, it looks like no matter how hard we try, we're not going to meet the mission of the National Park Service in the strictest sense, of trying to restore the fire regime that used to be there. That little personal crisis started leading me to question everything. At the time I was studying the potential effects of climatic change, and I started putting all the pieces together and realizing that even if we could completely restore the pre-European settlement fire regime, all these other things are happening that have no precedent.

We have a lot of ozone air pollution that comes into the park, and it particularly affects a few species of pines, and who knows what else it might affect. We're getting more nitrogen deposition from the atmosphere than we did in the past, from fossil fuel combustion. We have invasive species: If I look out my window here in the foothills, probably 90 percent of the species are introduced from different parts of the world. We have a non-native fungus that was introduced a long time ago, the white-pine blister rust, and that's slowly but surely killing off the sugar pines in the park. And then you throw rapid climatic change on top of all that, which, if the models are correct, is going to become a bigger and bigger issue in the very near future. I just reached this crisis point where I said, my gosh, we can't go back to a "natural" past, it's just too late for that. And then I started to ask, well, what the heck do you do?

A point I try to bring home to people is that, for good reason, we have a tendency to look to the past, to try to find an analog to current conditions. That provides a comfort factor where, if we can figure out what our ecosystem looked like 500 years ago and restore it to look like that, we ought to be okay. But the environments we have today have no analog in the past, and so we don't have that extra comfort zone anymore of being able to look to the past and say, here's my model for what I want my ecosystem to look like.