Introduction

Conservation biology means different things to different people. For the purposes of this course, conservation biology covers all of those topics that I have chosen to include in the course and none of those topics that I haven't chosen to include. Seriously though, there are reasons I chose what I chose to include. To understand what they are, it may help to begin with a little history.

I don't think I have to convince anyone in this room that the world we now live in is far different from the one that was here a few thousand years ago. The reason for that difference is two-fold: the growth of human populations and the enormous resource demands we make on the planet.

• THE ENORMOUS INCREASE IN HUMAN POPULATION. The world had fewer than 3 billion people in in when I was born.¹ It reached 6 billion people in 1999. The increase has been faster than exponential (Figure 1).

  Figure 1: Human population growth over the last 10,000 years.

  

• That's the bad news. THE GOOD NEWS IS THAT RATES OF POPULATION GROWTH APPEAR TO HAVE SLOWED. The best guess from the United Nation's population program is that world population will level off at about 9 billion in 2050 (Figure 2). Of course, 9 billion people is a lot of people, and it means adding as many people to the plant in the next fifty years as were alive when I was born.

  Figure 2: Population projections for human populations through 2050.

  

• THE ENORMOUS RESOURCE DEMANDS WE MAKE ON THE PLANET. Our numbers alone would be enough to ensure a great impact, but we also use many of the planet's resources. Peter Vitousek, Pam Matson, and Paul Ehrlich [6] estimated almost 20 years ago that human beings capture over 40% of global net primary productivity, meaning that we are responsible for consuming nearly half of the annual energy input into the world's ecosystems. A more recent attempt to estimate the same quantity [4] emphasizes how little we now about our cumulative impact. Nonetheless, the authors estimate that humans appropriate at least 10% and possibly as much as 55% of terrestrial net photosynthetic production (TNPP). Their best estimate is that we appropriate about 32% of TNPP.

• But that's only the impact we have on net primary production. I can't do it, but it's conceivable that someone smarter than I am could imagine a scenario in which humans co-opt 50% of net primary production without a significant impact on other inhabitants of the earth. I can't come up with a sustainable scenario that allows us to co-opt 50% of net primary productivity because of how much we've already altered the face of the planet [7].
  • 10-15% of the earth's land surface is occupied by row-crop agriculture or by urban-industrial areas, and another 6-8% has been converted to pastureland. Total affected: between 15 and 25%, 40-50% of land surface has been transformed or degraded.

  • 22% of marine fisheries are overexploited or depleted, another 44% are at their limit of exploitation.

  • Humans use about 50% of the runoff water that is fresh and reasoably accessible. Human activities add at least as much fixed nitrogen to terrestrial ecosystems as all other sources combined.

  • Human activities are now responsible for fixing as much nitrogen as all terrestrial nitrogen fixation by bacteria, and anthropogenic nitrogen fixation is projected to increase by more than 60% between now and 2050 (Figure 3).

    Figure 3: Current and projected rates of annual nitrogen fixation due to human activities [1]

    

All in all, 83% of the earth's land surface has been directly influenced by human activities (Figure 4), and our impact is pervasive in densely populated areas like the northeastern United States (Figure 5). Peter Kareiva and colleagues point out that ``we have domesticated landscapes and ecosystems in ways that enhance our food supplies, reduce exposure to predators and natural dangers, and promote commerce'' [3, p. 1866]

Figure 4: The human footprint index reflects human population density, land transformation, access, and electrical power infrastructure [5]

Figure 5: The human footprint index clearly shows metropolitan areas in the northeastern United States. In addition to Boston and New York, which are labeled, it's easy to pick out Providence, RI, Hartford, CT, Springfield, MA, Worcester, MA, and Portland, ME. If you know the freeways in the area, it's not hard to pick out I-95, I-91, I-90, and others.

The Millenium Ecosystem Assessment [1] summarizes the four key findings of their study this way:

• Over the past 50 years, humans have changed ecosystems more rapidly and extensively than in any comparable period of time in human history, largely to meet rapidly growing demands for food, fresh water, timber, fiber, and fuel. This has resulted in a substantial and largely irreversible loss in the diversity of life on Earth.

• The changes that have been made to ecosystems have contributed to substantial net gains in human well-being and economic development, but these gains have been achieved at growing costs in the form of the degradation of many ecosystem services, increased risks of nonlinear changes, and the exacerbation of poverty for some groups of people. These problems, unless addressed, will substantially diminish the benefits that future generations obtain from ecosystems.

• The degradation of ecosystem services could grow significantly worse during the first half of this century and is a barrier to achieving the Millennium Development Goals.

• The challenge of reversing the degradation of ecosystems while meeting increasing demands for their services can be partially met under some scenarios that the MA has considered, but these involve significant changes in policies, institutions, and practices that are not currently under way. Many options exist to conserve or enhance specific ecosystem services in ways that reduce negative trade-offs or that provide positive synergies with other ecosystem services.

In the United States, it is possible to recognize three different responses to these problems. Groom et al. [2] refer to these responses as ``ethics'' because each is intended to provide guidance about how we should act and the choices we should make with regard to our interaction with nature.

• THE ROMANTIC-TRANSCENDENTAL CONSERVATION ETHIC

  In the mid-nineteenth century Ralph Waldo Emerson, Henry David Thoreau, and John Muir waxed eloquent about the wonders of nature in a mystical, almost religious language. Their writings convinced many of the need to save wild places, regardless of whether those places provide any direct economic benefit. The Sierra Club, which was among the earliest of the formal conservation organizations, grew out of Muir's efforts to protect Yosemite and other parts of the Sierra Nevada.

• THE RESOURCE CONSERVATION ETHIC

  In the late nineteenth century Gifford Pinchot, Teddy Roosevelt, and others recognized that it was in our own best interest to protect at least some portions of the natural world. Their motivation for doing so, however, was that we derived important ``natural resources'' from the earth. Unlike the philosophical conservationists, who hoped to protect natural areas for their own sake, Pinchot and the utilitarians hoped to protect natural areas for what they could do for us.

• THE EVOLUTIONARY-ECOLOGICAL LAND ETHIC

  The most eloquent exposition of this approach is, of course, in Aldo Leopold's A Sand County Almanac. It is, in many ways, a synthesis of the preceding two. It lacks, mostly, the quasi-religious overtones of Thoreau and Muir, and it lacks the strictly utilitarian approach of Pinchot. Fundamentally, the land ethic recognizes that we do derive benefits from nature, but the connectedness of ecological systems means that it is difficult, if not impossible, to identify only some components as useful.

  The first rule of an intelligent tinkerer is to keep all of the pieces. Aldo Leopold, The Round River

We'll return to a more complete discussion of these ethical issues in the last lectures of this course. For now I just want to point out that the first and third of these ethics are widely accepted within conservation circles, but only the second has been persuasive to those not already committed to conservation. As a result conservation efforts, especially those prior to about 1960, were predominantly either concerned with:

• Land conservation - setting aside parcels of land for protection and public enjoyment or for scientific research, e.g., the NATURE CONSERVANCY.

• Wildlife conservation - management of game animal populations to provide opportunities for hunting, fishing, and observation, e.g., the AUDUBON SOCIETIES and the NATIONAL WILDLIFE FEDERATION.

Interestingly, conservation efforts, at least until the early 1960's, were almost entirely concerned with biological conservation. In the 1950s and especially in the 1960s, these concerns broadened into more general concerns about pollution and population (Rachel Carson, Silent Spring; Paul Ehrlich, The Population Bomb). Still, academic biologists in departments of botany, zoology, or biology² were little involved in providing advice to resource managers charged with protecting endangered species or with managing parks and nature reserves. Resource managers were trained largely in departments of forestry, natural resources, and wildlife management - departments whose faculty often had little contact with colleagues doing basic research in ecology, evolutionary biology, and systematics.³

In the late 1970s and early 1980s Mike Soulé and others in traditional biology departments began describing the need for a field of conservation biology that would take the basic principles of ecology, evolutionary biology, and systematics and apply them to the problem of saving endangered species. Soulé and Bruce Wilcox edited a book, published in 1981, that those in traditional biologists often regard as the founding document of the field.⁴ In the nearly twenty-five years since Soulé and Wilcox a SOCIETY FOR CONSERVATION BIOLOGY has been founded, programs in conservation biology have sprouted (often in departments of forestry and natural resources) around the country, and traditional biologists have shown increasing interest in the questions conservation biologists pose. The focus of the field has also broadened. Two strains can be recognized within it:

• Conserving endangered species - Demographic and genetic consequences of small population size, population viability analysis, biology of small popualtions, manipulative techniques that enhance survival probability and design of nature reserves for particular species.

• Conserving functional and structural aspects of important ecosystems - Diversity and stability of ecological communities, habitat fragmentation, landscape ecology, island biogeography, and restoration ecology

More recently, we've come to realize that the idea that there's a ``nature'' out there separate from human influence is wrong. There are degrees of human influence, or domestication as Kareiva et al. [3] call it. The course roughly follows these themes.