SPEECH USDA Forest Service Washington, D.C.

Managing the National Forest System: Great Issues and Great Diversions

Forest Service Chief Dale Bosworth
Commonwealth Club
San Francisco, CA—April 22, 2003

Thank you for that nice introduction and for the opportunity to be here at the Commonwealth Club. I’ve been scheduled for some time to be here in the Bay Area to participate in the University of California Forestry School’s William Main Distinguished Visitor Program. I’ll be doing that later today. But I wanted an additional opportunity to talk about some issues that I’ve begun to feel very strongly about, based on my experience as Forest Service Chief. So I want to thank the Commonwealth Club for giving me that chance here this morning.

I have had the honor of serving as Chief of the Forest Service for 2 years now, and I’ve been with the agency for 37 years. Actually, it’s been a lot longer than that, because I grew up on national forests in California. My father was a Cal forestry graduate in 1939, and he served in various positions with the Forest Service on several national forests. He was forest supervisor just across the Valley on the Eldorado National Forest. So I have a lifetime of Forest Service experience—or, actually, two lifetimes of experience, and after I retire, it will continue through my son, who is also a forester and works for the Forest Service.

Personal Bias

A strong personal bias comes from those lifetimes of experience. I think the 192 million acres of national forests and grasslands in America are truly a national treasure. More than 20 million of those acres are right here in California—I think it’s something like 20 percent of your great state. The national forests are some of the most outstanding places in this country. They serve as America’s outdoor playground, and they contain a wealth of wildlife and other natural resources. Best of all, they are owned by the public—by you and me.

With that ownership comes the right and, some would say, maybe even the obligation to care about how these national treasures are administered and managed, and even to have strong opinions about it. And with those opinions naturally comes debate. I’ve served as a line officer at every level of the organization, from district ranger, to forest supervisor, to regional forester, and now to Chief. So I’m well acquainted with those debates. I’ve been right in the middle of them.

As Chief, my greatest challenge is getting my hands around the critical issues in the right way and deciding where to go and what to spend my time on. As I’ve struggled with this for the past couple of years, I have concluded that the current debate about the administration and management of America’s national forests—and, believe me, there is a great deal of vociferous debate—is about the wrong issues.

Wrong in what way? Well, I think the debate focuses on the wrong issues for the beginning of the 21st century. They are the wrong issues if we’re ever going to meet the great challenges to the future of the national forests and grasslands in this country.

What I want to do today, on Earth Day, is to talk about the issues—the wrong issues and the right ones. I chose Earth Day in the spirit of the founders of Earth Day in 1970, who focused on the right issues for the time. Hopefully, my remarks will help start a public dialogue and, yes, even a debate on the great issues—the right issues—facing us today. That way, I hope we can reengage and reshape the debate. I hope we can stop being distracted by yesterday’s issues and start focusing on the issues we face today.

Speaking of Earth Day, the first Earth Day was 33 years ago. I was 4 years into my Forest Service career and working on a ranger district. I was asked—no, probably told—by my district ranger to go and talk about conservation to a class of third graders. We had a great morning, for three reasons: First, they were well behaved; second, I had their total attention; third, not one of them disagreed with anything I had to say.

I expect the same here today—well, maybe not. At least I can hope for the first two.

Now to the great issues facing the national forests and grasslands. Someone once put it this way: There are great issues and great diversions. Great issues are matters that cry out for public attention and resolution. Great diversions are relatively unimportant matters that take up a lot of our time and effort.

What I want to do today is to separate the great issues in national forest management from the great diversions. As I see it, there are four great issues that the Forest Service faces on the national forests and grasslands, and there are at least that many great diversions.

Fire and Fuels

One great issue is fire and fuels. Last year, we had our second biggest fire season since the 1950s. California was in the middle of it. Four states had record fires last year, and California came close with the McNally Fire.

The underlying issue is that so many of our forests have become overgrown and unhealthy. I don’t want to oversimplify—many forests are healthy, and some forest types were always dense. But on the national forests alone, 73 million acres adapted to frequent fire are at risk from wildland fires that could compromise human safety and ecosystem health.

Ponderosa pine is a prime example. Historically, most ponderosa pine forests were relatively open, with a few dozen trees per acre. Today, they might have hundreds or even thousands of trees per acre. Just to give you some idea, in the Southwest—Arizona and New Mexico—annual growth is enough to cover a football field 1 mile high with solid wood, even after losses from mortality. Recent removals have been only about 10 percent of this.

In a drought, all those trees can fuel a catastrophic fire. Think of it as an environmental debt, like a toxic dump. It will take decades of action to clean up, provided we as a society are willing to focus on this issue and commit the needed resources.

Americans must decide: We can remove some of the trees and lower the risk of catastrophic fire; or we can do nothing and watch them burn. I think the choice is obvious: In a good part of the West—where forests are overgrown—we must return forests to the way they were historically, then get fire back into the ecosystem when it’s safe.

At the same time, we’ve got tens of millions of acres of healthy fire-adapted forest. We’ve got to keep them healthy. That means getting fire back into the ecosystem now.

That’s exactly what we’re trying to do right here in California through the Sierra Nevada Framework. We’ve got a huge fire and forest health problem up in the Sierras, and we’re trying to restore the ecosystem to something more like its condition at the time of European settlement.

But if you read the papers, you’d think we’re just trying to get out more of the cut. And that’s the first great diversion—the bogus debate over logging. It’s just plain wrong. Today, our primary purpose for timber removal is not what it was 20 years ago. In most places—including here in California—it’s to improve wildlife habitat, reduce hazardous fuels, or restore ecosystem health. Most wood fiber from the national forests today is a byproduct. So it’s not primarily about logging for lumber, folks. Not anymore. The issue is fire and fuels.

Invasive Species

The second great issue is the spread of invasive species. We used to focus just on noxious weeds. But now we know that the issue is far broader.

California alone has more than a thousand nonnative species, including invasive weeds like cheatgrass, brooms, and thistles. These plants soak up the water and take up the space, driving out the native plants. One example on the national forests south of here is giant reed. It dries up creeks and destroys habitat needed by at least four threatened and endangered species, including the California red-legged frog. We’re losing our national treasures.

Nationwide, invasive weeds now cover an area about a third larger than the state of California. Each year, they gobble up an area larger than Napa and Sonoma Counties combined. Areas infested with weeds like leafy spurge lose almost all their forage value for both livestock and wildlife.

Invasives are not limited to plants. A big threat to the red-legged frog is the bullfrog, which isn’t native here. Nonnative fish have driven more than half of the fish species native to the arid Southwest to the edge of extinction. Chestnut blight alone virtually wiped out an entire forest type in the East, the oak/chestnut forest. Every region has its own major problem with invasive and nonnative species—gypsy moth in the Northeast, kudzu vine in the South, white pine blister rust in the West. All invasives combined cost Americans about $138 billion per year in total economic damages and associated control costs.

The ecological costs are even worse. The Nature Conservancy and NatureServe sponsored a recent study on the major causes of biodiversity loss in the United States. The study found that invasives have contributed to the decline of almost half of all imperiled species.

So this is a huge issue for the Forest Service, and it should be for all Americans. Public lands—especially federal lands—have become the last refuge for endangered species—the last place where they can find the habitat they need to survive. If invasives take over, these imperiled animals and plants will have nowhere else to go.

The problem is, Americans have become too focused on the symptoms of the problem—individual endangered species. We do have to manage specific habitats for species at risk; I strongly support the Endangered Species Act. But we’ve also got to consider long-term outcomes across the entire landscape. If we’re going to rise to landscape-level challenges like catastrophic fire or invasive species, then we’ve got to do both. We can’t focus entirely on individual species.

So the great diversion is all the publicity surrounding individual endangered species and the efficacy of the regulatory system. This or that species becomes a poster child for inflaming passion and fueling debate. As a result, most of our time and energy is spent on this or that individual species—like Canada lynx or spotted owl—and not enough on the underlying issues—things like invasive species. We need to focus more on the causes of biodiversity loss on a landscape level—habitat loss and invasives—and less on the symptoms—the poster children—this or that individual species.

Habitat Fragmentation

That brings me to the third great issue—habitat fragmentation through land conversion. Every day, we lose about 4,000 acres of open space to development. That’s almost 3 acres per minute. And the rate of conversion is getting faster all the time.

How does that affect the national forests and grasslands? Years ago, the national forests were buffered by miles of rural landscape. Now they are increasingly part of the wildland/urban interface. People are paying lots of money to live close to or adjacent to public lands. Demands for services are growing, and so is the challenge of fire protection.

But maybe the biggest threat is to wildlife. Overall, we’re losing forest interior habitat as large working forests are sold and developed. America is losing valuable corridors needed to connect parts of the national forests with other large undisturbed tracts of land. Animals like marten, bear, or cougar need large, relatively undisturbed forests to survive. Unfortunately, we as a nation are gradually losing them.

We’re also losing open areas of range that animals like elk need to survive. Most people don’t realize that the Forest Service manages so much rangeland—about 40 percent of national forest land is range. When ranchers settled the West, they homesteaded on the bottomland, where the water was. They used the dry uplands for grazing, but most of that stayed in the public domain. Eventually, it came under stewardship by the Forest Service or the Bureau of Land Management.

When the Forest Service first started managing the land a century ago, overgrazing was a huge problem. Over time, we improved things by working closely with the ranchers. The ecological payoff has been enormous—we kept the land whole. Those wetter bottomlands are ecologically tied to the drier uplands. Species all across the landscape depend on both, including the cattle. The grazing allotments we’ve got, if they’re done right, work well for the land.

But now we face a huge new issue. Our population is growing, particularly in the West—and especially in counties with national forests, which are huge retirement magnets. Developers often target the adjacent bottomlands. Millions of acres of ranchland have been converted to ranchettes and condominiums. That means we’re losing the ecological integrity of the land as a whole. Elk, for example, depend on bottomland for winter range. Without it, they won’t survive, no matter how good the habitat is on adjacent public land.

So the great issue is land conversion and habitat fragmentation, but Americans have often lost focus of the issue. Often, they focus instead on livestock grazing on public lands. Some say overgrazing is a huge and intractable problem on the national forests and grasslands.

Yes, there are places where overgrazing is a concern. We need to make sure that we’re managing every acre of grazing allotment for the right kind and amount of grazing. But we’re already doing that a whole lot more than you might think from reading the papers. Some 85 percent of our grazing allotments are in good or improving condition. The vast majority of our allotments are in a better condition today than they were a century ago.

So the great diversion is grazing on public lands. Americans should be focusing instead on how to buffer the national forests by protecting open land—by keeping ranches and working forests in operation. The Forest Service has some good programs for that. We’ve got conservation easements through the states so that willing landowners can keep their lands forested. We’ve also got forage reserves that ranchers can use to give their allotments a rest. Through programs like these, we can work together across the landscape to keep the land whole, in the best tradition of conservation.

Unmanaged Recreation

The fourth great issue is unmanaged outdoor recreation. In my 37 years with the Forest Service, I have seen a tremendous growth in the amount of recreation on the national forests. Last year, we had 214 million visitors, which is just phenomenal. And it’s only going to keep on growing—we expect it to more than double by the end of the century.

I think that’s great. We want the American people to use their national forests and grasslands. It gives them a stake in the land. It gives them a sense of place. It helps them understand why we in the Forest Service are so passionate about the land—why we think it’s so worth protecting.

The issue is this: Back when we had light recreational use, we didn’t need to manage it; but now that it’s heavier, we do. There are still uses like blueberry picking that we don’t need to manage. But if every blueberry was picked, we would need to manage it. At one time, we didn’t manage mushroom picking; but now we do in some areas because the use has gotten so heavy.

At one time, we didn’t manage the use of off-highway vehicles, either. OHVs are a great way to experience the outdoors, and only a tiny fraction of the users leave lasting traces by going cross-country. But the number of people who own OHVs has just exploded in recent years. In 2000, it reached almost 36 million. Even a tiny percentage of impact from all those millions of users is still a lot of impact. Each year, we get hundreds of miles of what we euphemistically refer to as “unplanned roads and trails.”

For example, the Lewis and Clark National Forest in Montana has more than a thousand unplanned roads and trails reaching for almost 650 miles. That’s pretty typical for a lot of national forests, and it’s only going to get worse. We’re seeing more and more erosion, water degradation, and habitat destruction. We’re seeing more and more conflicts between users. We’re seeing more damage to cultural sites and more violation of sites sacred to American Indians. And those are just some of the impacts. We’re going to have to manage that by restricting OHV use to designated roads, trails, and areas.

So the great issue is unmanaged recreation—and the great diversion is all the roads the Forest Service is supposedly building to get out the cut. That’s just plain not true. Here are the facts:

• In the last 5 years, we have added some road—about 150 miles on average each year.
• The purpose varied. In some cases, it was to help recreational users get somewhere. In other cases, it might have been for fire protection, fuels reduction, ecosystem restoration, or—in places like Alaska—jobs and timber.
• But for every mile of road we added, we decommissioned 14 miles of road. In fact, we decommissioned more than 10,000 miles of road in the last 5 years!

So our road system is not growing, it’s actually shrinking. We’ve got it turned around. Thirty years ago, roadbuilding might have been a problem. Now it’s not. Now it’s a great diversion that keeps us from focusing on the great issue at hand: unmanaged recreation.

Spirit of Earth Day

In closing, let me summarize: We’ve got four great issues facing us as we open this century—fire and fuels; invasive species; habitat fragmentation; and unmanaged recreation. Unfortunately, we’ve also got some great diversions, like logging and roadbuilding. In that connection, let me go back to that study on biodiversity loss by The Nature Conservancy and NatureServe.

The study ranks the causes of biodiversity loss. Invasive species are at the top of the list. Farther down come land conversion for development; outdoor recreation; and disrupted fire regimes—fire and fuels. Toward the bottom of the list you finally get to the combined effects of logging and logging roads. Even OHV use alone affects more imperiled species than logging and logging roads combined.

So why do we spend so much of our time debating logging and roads? Shouldn’t we be focusing more on these other issues instead?

With that said, the study did find that logging and logging roads do affect some imperiled species. It’s not necessarily on the national forests, because the study covered the whole United States. But I still think that’s unacceptable. That’s why the Forest Service is so careful about designing our vegetation management projects to achieve the desired future condition. In fact, our vegetation treatments are often wholly or partly designed exactly for that purpose—to protect long-term biodiversity.

Is it working? Well, another study sponsored by The Nature Conservancy and NatureServe points out something interesting: The greatest number of imperiled species in the United States is not found on wildlife refuges or national parks, where some people might expect. It’s found on the National Forest System. It’s about a quarter of all imperiled species nationwide—26 percent. It’s about half of all the populations of federally listed species found on federal lands.

Why? Is it because the Forest Service is doing something to endanger these species? No, it’s because the national forests and grasslands have always been the best refuges—the best places for endangered species to make a final stand. That’s why it’s so important to address the great issues—fire and fuels, invasive species, habitat fragmentation, and unmanaged recreation. These are the biggest threats to biodiversity on the national forests and grasslands. We must actively manage them if we truly want to keep national forests as America’s last, best refuges.

That brings me back to Earth Day. Like the founders of Earth Day, the Forest Service recognizes our enormous responsibility to protect America’s species at risk. But we can’t do it alone. We can’t do it as long as we as a nation let ourselves get distracted by the great diversions. We can’t do it unless all of us start focusing on the great issues—fire and fuels, invasive species, habitat fragmentation, and unmanaged recreation.

I think that’s what Earth Day is all about. It’s about a shared responsibility to care for the land. We’re all in this together. The national forests and grasslands are great national treasures. We all cherish these lands and the values they protect—wildlife, water, forests, and more. We are all concerned about their health. For the sake of the future, I think we’ve got to come together. We’ve got to stop focusing on the great diversions and start focusing on the great issues. We owe our children and grandchildren at least that much.

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¹Sen. Bob Bennett (R-UT), speaking about national health care issues. Mark Rey, personal communication, 1 April 2003 (Under Secretary of Agriculture for Natural Resources and the Environment).

²In 2002, 6.9 million acres burned, according to the National Interagency Fire Center in Boise, ID (http://www.nifc.gov/stats/wildlandfirestats.html). Except for 2000, when 8.4 million acres burned, that is more than in any year since the 1950s, when 9.4 million acres burned each year on average.

³California had 8,328 reported fires, and 506,696 acres burned. National Interagency Coordinating Center, “National Report: Wildland Fires and Acres Burned by State, 2002,” National Interagency Fire Center, Boise, ID (http://www.nifc.gov/news/2002_StatsSumm/fires_acres.pdf).

⁴In forests with a long fire return interval (200+ years), only 1 percent on national forest land show a severe deviation from the historical condition. These naturally dense forest types include spruce/fir and coastal Douglas-fir/western hemlock. See Kirsten M. Schmidt, James P. Menakis, Colin C. Hardy, Wendel J. Hann, and David L. Bunnell, Development of Coarse-Scale Spatial Data for Wildland Fire and Fuel Management (GTR RMRS-87; USDA Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, Missoula, MT), p. 14.

⁵Classified as condition classes 2 and 3 (moderate to severe deviation from historical condition) in fire regimes I (low-severity fires every 1 to 35 years—e.g., pine, oak, pinyon/juniper) and II (stand replacement fires every 1 to 35 years—e.g., grassland, chaparral, sagebrush), these lands are considered priority areas for treatment. See Schmidt and others, pp. 12-14.

⁶Stephen F. Arno, “Fire in Western Forest Ecosystems,” in James K. Brown and Jane Kapler Smith (eds.), Wildland Fire in Ecosystems: Effects on Flora (Gen. Tech. Rep. RMRS-GTR-42-vol. 2; Ogden, UT: USDA Forest Service, Rocky Mountain Research Station, 2000), p. 101.

⁷Marlin A. Johnson, “Combining Social and Ecological Needs on Federal Lands: A Global Perspective” (unpublished paper; USDA Forest Service, Forestry and Forest Health Staff, Albuquerque, NM), p. 4.

⁸In this context, catastrophic fires are fires that can compromise human safety and ecosystem integrity. They often have a severity outside the historical range of variation.

⁹Marlin A. Johnson, “Changed Southwest Forests: Resource Effects and Management Remedies” (paper; National Convention, Society of American Foresters, Forest Ecology Working Group; 9-13 November 1996; Albuquerque, NM), p. 3.

¹⁰The General Accounting Office has estimated necessary treatment costs over 15 years at $12 billion (U.S. General Accounting Office, Western National Forests: A Cohesive Strategy Is Needed to Address Catastrophic Wildfire Threats [GAO/RCED-99-65; April 1999], p. 8). Another study calculated that a single round of treatments across the entire National Forest System—a “worst-case scenario,” because treatment on every acre is unnecessary, infeasible, and undesirable—would cost $64.2 billion (Maitland Sharpe, “Excess Fuels and Fuels Treatments on the National Forest System” [unpublished paper, 11 April 2003; USDA Forest Service, Washington Office, Policy Analysis Staff, Washington, DC], table 4).

¹¹Invasive species include both native and nonnative forest and rangeland pests that are likely to cause economic or environmental harm or harm to human health. They usually spread unchecked by environmental controls such as native predators, displacing native species through competition, predation, parasitism, or by other means.

¹²Traditionally, noxious weeds were generally viewed as plants that could adversely affect agriculture, livestock, or human health. The definition has broadened to include adverse ecological impacts. Today, the term noxious weeds is virtually synonymous with the term invasive weeds.

¹³USDA Forest Service, “Invasive Plant Information” (Invasive Plant EIS Team, Pacific Northwest Region, Portland, OR [www.fs.fed.us/r6/invasiveplant-eis/plantinfo.html]).

¹⁴Invasive plants now cover about 133 million acres in all ownerships nationwide, and they are expanding at the rate of about 1.7 million acres per year. USDA Forest Service, “Destroying the Silent Invaders: A Forest Service Strategy to Control Invasive Weeds” (unpublished draft report, 23 December 2002; Washington Office, Forest Management Staff, Washington, DC), p. 2.

¹⁵Of 43 fish species that are native to the arid Southwest, 23 are listed as endangered, partly due to competition from nonnative fish. Donald DeLorenzo, “Native Fish Management and Recovery—Regional Scale Perspective of Aquatic Species,” in: USDA Forest Service, Southwestern Region, The Southwestern Region: Uniquely Prepared for a Second Century of Service (Chief’s Review, October 2002), p. 60.

¹⁶David Pimentel, Lori Lach, Rodolfo Zuniga, and Doug Morrison, “Environmental Economic Costs Associated With Nonindigenous Species in the United States” (unpublished paper, 12 June 1999; College of Agricultural and Life Sciences, Cornell University, Ithaca, NY [http://www.news.cornell.edu/releases/Jan99/species_costs.html]), p. 14.

¹⁷David S. Wilcove, David Rothstein, Jason Dubow, Ali Phillips, and Elizabeth Losos, “Leading Threats to Biodiversity: What’s Imperiling U.S. Species,” in Bruce A. Stein, Lynn S. Kutner, and Jonathan S. Adams (eds.), Precious Heritage: The Status of Biodiversity in the United States (Oxford, U.K.: Oxford University Press, 2000), p. 242.

¹⁸In this context, habitat fragmentation is the division of habitat in both forest and rangeland ecosystems into smaller, more isolated patches, posing a threat to the health and sustainability of ecosystems.

¹⁹From 1982 to 1997, more than 21.8 million acres of open land were converted to developed land. USDA Natural Resources Conservation Service, Natural Resources Inventory Summary Report (http://www.nrcs.usda.gov/technical/NRI/1997/summary.report/), table 5.

²⁰By 1997, the rate of development had doubled in just 5 years. H. Ken Cordell and Christine Overdevest, Footprints on the Land: An Assessment of Demographic Trends and the future of Natural Lands in the United States (Champaign, IL: Sagamore Publishing, 2001), p. 98.

²¹By 2020, the U.S. population is expected to grow by 50 million. Of the 80 high-growth retirement destinations nationwide, 74 percent abut or contain national forest land. Cordell and Overdevest, p. 58, 129.

²²From 1982 to 1997, 3.2 million acres of rangeland were converted to ranchettes and condominiums. NRCS, table 5.

²³John E. Mitchell, Rangeland Resource Trends in the United States: A Technical Document Supporting the 2000 USDA Forest Service RPA Assessment (RMRS-GTR-68; Fort Collins, CO: USDA Forest Service, Rocky Mountain Research Station, 2000), p. 39.

²⁴Since 1946, the number of visitors to the national forests and grasslands has grown 18 times. USDA Forest Service, “National Forest Recreation Use, 1924-1996” (Washington, DC: Recreation, Heritage and Wilderness Staff, 1997). Visitation data collected before 2000 are not absolutely reliable, but because they were consistently collected in the same way, they do measure the growth in recreational use.

²⁵USDA Forest Service, “National Forest Visitor Use Monitoring: National and Regional Project Results” (Washington, DC: USDA Forest Service, Recreation, Heritage and Wilderness Staff, September 2002), table 1.

²⁶By 2100, the U.S. population is expected to more than double from 275 million to 571 million (Cordell and Overdevest, p. 59), and the phenomenal rate of recreational growth on the National Forest System is likely to disproportionately increase the number of recreational users.

²⁷In this context, OHVs are wheeled motorized vehicles capable of traveling cross-country (i.e., away from established roads and trails).

²⁸The number of users has climbed from about 5 million in 1972 [Executive Order 11644 (President Richard M. Nixon, 1972]), to 19.4 million in 1983, to 27.9 million in 1995, to 35.9 million in 2000 (H. Ken Cordell, Jeff Teasley, Greg Super, John C. Bergstrom, and Barbara McDonald, Outdoor Recreation in the United States: Results from the National Survey on Recreation and the Environment [Asheville, NC: USDA Forest Service, Southeastern Research Station], ch. 2: Outdoor Recreation Participation, p. 8, table 2.1; NSRE 2000, table 2).

²⁹The forest estimates 1,348 unplanned roads and trails reaching for 646 miles. Ruth Roberson, personal communication (Resource Information Manager, Lewis and Clark National Forest, USDA Forest Service, 3 March 2003).

³⁰Patricia A. Stokowski and Christopher B. LaPointe, “Environmental and Social Effects of ATVs and ORVs: An Annotated Bibliography and Research Assessment” (unpublished paper; 20 November 2000, School of Natural Resources, University of Vermont, Burlington, VT); Richard B. Taylor, “Literature Review: The Effects of Off-Road Vehicles on Ecosystems” (Certified Wildlife Biologist, Texas Parks and Wildlife [http://www.tpwd.state.tx.us/texaswater/rivers/]).

³¹From 1998 to 2002, 777.4 miles of road were added (about 155 miles per year). During the same period, 10,790.2 miles of road were decommissioned (about 2,158 miles per year). USDA Forest Service, Engineering statistics for roads, 1998-2002 (unpublished tables, 4 February 2003; Washington Office, Engineering Staff, Washington, DC).

³²Wilcove and others, pp. 242-247. The study found that the two leading causes of biodiversity loss on all ownerships nationwide are habitat loss and degradation (affecting 85 percent of the species studied) and invasive species (49 percent). Because habitat loss and degradation are due to 11 different subfactors, the largest single cause of biodiversity loss can be said to be invasives. Within habitat loss and degradation, land conversion affects 35 percent, recreation affects 27 percent (including OHVs—13 percent), disruption of fire ecology affects 14 percent, and logging/logging roads combined affect 12 percent.

³³Craig R. Groves, Lynn S. Kutner, David M. Stoms, Michael P. Murray, J. Michael Scott, Michael Schafale, Alan S. Weakley, and Robert L. Pressey, “Owning Up to Our Responsibilities: Who Owns Lands Important for Biodiversity?” in Bruce A. Stein, Lynn S. Kutner, and Jonathan S. Adams (eds.), Precious Heritage: The Status of Biodiversity in the United States (Oxford, England: Oxford University Press, 2000), pp. 280, 282.