Conservation Biology

        Although the direct impacts of defaunation driven by overhunting can be predicted to some degree, higher-order indirect effects on community structure remain poorly understood since Redford’s (1992) seminal paper and may have profound, long-term consequences for the persistence of other taxa, and the structure, productivity and resilience of terrestrial ecosystems (Cunningham et al. 2009). Severe population declines or extirpation of the world’s megafauna may result in dramatic changes to ecosystems, some of which have already been empirically demonstrated, while others have yet to be documented or remain inexact. Large vertebrates often have a profound impact on food webs and community dynamics through mobile-linkage mutualisms, seed predation, and seedling and sapling herbivory. Plant communities in tropical forests depleted of their megafauna may experience pollinationbottlenecks, reduced seed dispersal, monodominance of seedling cohorts, altered patterns of seedling recruitment, other shifts in the relative abundance of species, and various forms of functional compensation (Cordeiro and Howe 2003; Peres and Roosmalen 2003; Wang et al. 2007; Terborgh et al. 2008; Chapter 3). On the other hand, the net effects of large mammal defaunation depends on how the balance of interactions are affected by population declines in both mutualists (e.g. highquality seed dispersers) and herbivores (e.g. seed predators) (Wright 2003). For example, significant changes in population densities in wild pigs (Suidae) and several other ungulates and rodents, which are active seed predators, may have a major effect on seed and seedling survival and forest regeneration (Curran and Webb 2000).

               Tropical forest floras are most dependent on large-vertebrate dispersers, with as many as 97% of all tree, woody liana and epiphyte species bearing fruits and seeds that are morphologically adapted to endozoochorous (passing through the gut of an animal) dispersal (Peres and Roosmalen 2003). Successful seedling recruitment in many flowering plants depends on seed dispersal services provided by large-bodied frugivores (Howe and Smallwood 1982), while virtually all seeds falling underneath the parent’s canopy succumb to density-dependent mortality—caused by fungal attack, other pathogens, and vertebrate and invertebrate seed predators (see review in Carson et al. 2008). A growing number of phytodemographic studies have examined the effects of large-vertebrate removal. Studies examining seedling recruitment under different levels of hunting pressure (or disperser abundance) reveal very different outcomes. At the community level, seedling density in overhunted forests can be indistinguishable, greater, or less than that in the undisturbed forests (Dirzo and Miranda 1991; Chapman and Onderdonk 1998; Wright et al. 2000), but the consequences of increased hunting pressure to plant regeneration depends on the patterns of depletion across different prey species. In persistently hunted Amazonian forests, where large-bodied primates are driven to local extinction or severely reduced in numbers (Peres and Palacios 2007), the probability of effective dispersal of largeseeded endozoochorous plants can decline by over 60% compared to non-hunted forests (Peres and Roosmalen 2003). Consequently, plant species with seeds dispersed by vulnerable game species are less abundant where hunters are active, whereas species with seeds dispersed by abiotic means or by small frugivores ignored by hunters are more abundant in the seedling and sapling layers (Nuñez-Iturri and Howe 2007; Wright et al. 2007; Terborgh et al. 2008).

                However, the importance of dispersal- limitation in the absence of large frugivores depends on the degree to which their seed dispersal services are redundant to any given plant species (Peres and Roosmalen 2003). Furthermore, local extinction events in large-bodied species are rarely compensated by smaller species in terms of their population density, biomass, diet, and seed handling outcomes (Peres and Dolman 2000). Large vertebrates targeted by hunters often have a disproportionate impact on community structure and operate as “ecosystem engineers” (Jones et al. 1994; Wright and Jones 2006), either performing a key landscaping role in terms of structural habitat disturbance, or as mega-herbivores that maintain the structure and relative abundance of plant communities. For example, elephants exert a major role in modifying vegetation structure and composition as herbivores, seed dispersers, and agents of mortality for many small trees (Cristoffer and Peres 2003). Two similar forests with or without elephants show different succession and regeneration pathways, as shown by long-term studies in Uganda (Sheil and Salim 2004). Overharvesting of several other species holding a keystone landscaping role can lead to pervasive changes in the structure and function of ecosystems. For example, the decimation of North American beaver populations by pelt hunters following the arrival of Europeans profoundly altered the hydrology, channel geomorphology, biogeochemical pathways and community productivity of riparian habitats (Naiman et al. 1986). Mammal overhunting triggers at least two additional potential cascades: the secondary extirpation of dependent taxa and the subsequent decline of ecological processes mediated by associated species. For instance, overhunting can severely disrupt key ecosystem processes including nutrient recycling and secondary seed dispersal exerted by relatively intact assemblages of dung beetles (Coleoptera: Scarabaeinae) and other coprophagous invertebrates that depend on large mammals for adult and larval food resources (Nichols et al. 2009).

In the opening of Conservation Biology: An Evolutionary Ecological Perspective, Michael Soulé and Bruce Wilcox (1980) described conservation biology as “a mission-oriented discipline comprising both pure and applied science.” The phrase crisis-oriented (or crisis-driven) was soon added to the list of modifiers describing the emerging field (Soulé 1985). This characterization of conservation biology as a mission-oriented, crisis-driven, problem-solving field resonates with echoes of the past. The history of conservation and environmental management demonstrates that the emergence of problem-solving fields (or new emphases within established fields) invariably involves new interdisciplinary connections, new institutions, new research programs, and new practices. Conservation biology would followhis pattern in the 1970s, 1980s, and 1990s. In 1970 David Ehrenfeld published Biological Conservation, an early text in a series of publications that altered the scope, content, and direction of conservation science (e.g. MacArthur and Wilson 1963; MacArthur and Wilson 1967; MacArthur 1972; Soulé and Wilcox 1980; CEQ 1980; Frankel and Soulé 1981; Schonewald-Cox et al. 1983; Harris 1984; Caughley and Gunn 1986; Soulé 1986; Soulé 1987a) (The journal Biological Conservation had also begun publication a year earlier in England).

In his preface Ehrenfeld stated, “Biologists are beginning to forge a discipline in that turbulent and vital area where biologymeets the social sciences and humanities”. Ehrenfeld recognized that the “acts of conservationists are often motivated by strongly humanistic principles,” but cautioned that “the practice of conservation must also have a firm scientific basis or, plainly stated, it is not likely to work”. Constructing that “firm scientific basis” required—and attracted—researchers and practitioners from varied disciplines (including Ehrenfeld himself, whose professional background was in medicine and physiological ecology). The common concern that transcended the disciplinary boundaries was biological diversity: its extent, role, value, and fate. By the mid-1970s, the recurring debates within theoretical ecology over the relationship between species diversity and ecosystem stability were intensifying (Pimm 1991; Golley 1993; McCann 2000). Among conservationists the theme of diversity, in eclipse since Leopold’s day, began to re-emerge. In 1951, renegade ecologists had created The Nature Conservancy for the purpose of protecting threatened sites of special biological and ecological value. In the 1960s voices for diversity began to be heard within the traditional conservation fields. Ray Dasmann, in A Different Kind of Country (1968: vii) lamented “the prevailing trend toward uniformity” and made the case “for the preservation of natural diversity” and for cultural diversity as well. Pimlott (1969) detected “a sudden stirring of interest in diversity . . . Not until this decade did the word diversity, as an ecological and genetic concept, begin to enter the vocabulary of the wildlife manager or land-use planner.” Hickey (1974) argued that wildlife ecologists and managers should concern themselves with “all living things”; that “a scientifically sound wildlife conservation program” should “encompass the wide spectrum from one-celled plants and animals to the complex species we call birds and mammals.”

Conservation scientists and advocates of varied backgrounds increasingly framed the fundamental conservation problem in these new and broader terms (Farnham 2002). As the theme of biological diversity gained traction among conservationists in the 1970s, the key components of conservation biology began to coalesce around it:

Within the sciences proper, the synthesis of knowledge from island biogeography and population biology greatly expanded understanding of the distribution of species diversity and the phenomena of speciation and extinction.

The fate of threatened species (both in situ and ex situ) and the loss of rare breeds and plant germplasm stimulated interest in the heretofore neglected (and occasionally even denigrated) application of genetics in conservation.

Driven in part by the IUCN red listing process, captive breeding programs grew; zoos, aquaria, and botanical gardens expanded and redefined their role as partners in conservation.

Wildlife ecologists, community ecologists, and limnologists were gaining greater insight into the role of keystone species and top-down interactions in maintaining species diversity and ecosystem health.

Within forestry, wildlife management, range management, fisheries management, and other applied disciplines, ecological approaches to resource management gained more advocates.

Advances in ecosystem ecology, landscape ecology, and remote sensing provided increasingly sophisticatedconcepts and tools for land use and conservation planning at larger spatial scales.

As awareness of conservation’s social dimensions increased, discussion of the role of values in science became explicit. Interdisciplinary inquiry gave rise to environmental history, environmental ethics, ecological economics, and other hybrid fields.

As these trends unfolded, “keystone individuals” also had special impact. Peter Raven and Paul Ehrlich (to name two) made fundamental contributions to coevolution and population biology in the 1960s before becoming leading proponents of conservation biology. Michael Soulé, a central figure in the emergence of conservation biology, recalls that Ehrlich encouraged his students to speculate across disciplines, and had his students read Thomas Kuhn’s The Structure of Scientific Revolutions (1962). The intellectual syntheses in population biology led Soulé to adopt (around 1976) the term conservation biology for his own synthesizing efforts. For Soulé, that integration especially entailed the merging of genetics and conservation (Soulé 1980). In 1974 Soulé visited Sir Otto Frankel while on sabbatical in Australia. Frankel approached Soulé with the idea of collaborating on a volume on the theme (later published as Conservation and Evolution) (Frankel and Soulé 1981). Soulé’s work on that volume led to the convening of the First International Conference on Conservation Biology in September 1978.

The meeting brought together what looked from the outside like “an odd assortment of academics, zoo-keepers, and wildlife conservationists” (Gibbons 1992). Inside, however, the experience was more personal, among individuals who had come together through important, and often very personal, shifts in professional priorities. The proceedings of the 1978 conference were published as Conservation Biology: An Evolutionary- Ecological Perspective (Soulé and Wilcox 1980). The conference and the book initiated a series of meetings and proceedings that defined the field for its growing number of participants, as well as for those outside the immediate circle (Brussard 1985; Gibbons 1992). Attention to the genetic dimension of conservation continued to gain momentum into the early 1980s (Schonewald-Cox et al. 1983). Meanwhile, awareness of threats to species diversity and causes of extinction was reaching a broader professional and public audience (e.g. Ziswiler 1967; Iltis 1972; Terborgh 1974; Ehrlich and Ehrlich 1981). In particular, the impact of international development policies on the world’s species-rich, humid tropical forests was emerging as a global concern.

Field biologists, ecologists, and taxonomists, alarmed by the rapid conversion of the rainforests—and witnesses themselves to the loss of research sites and study organisms—began to sound alarms (e.g. Gómez-Pompa et al. 1972; Janzen 1972). By the early 1980s, the issue of rainforest destruction was highlighted through a surge of books, articles, and scientific reports (e.g.Myers 1979, 1980; NAS 1980; NRC 1982; see also Chapter 4). During these years, recognition of the needs of the world’s poor and the developing world was prompting new approaches to integrating conservation and development. This movement was embodied in a series of international programs, meetings, and reports, including the Man and the Biosphere Programme (1970), the United Nations Conference on the Human Environment held in Stockholm (1972), and the World Conservation Strategy (IUCN 1980). These approaches eventually came together under the banner of sustainable development, especially as defined in the report of the World Commission on Environment and Development (the “Brundtland Report”) (WCED 1987).

The complex relationship between developmentand conservation created tensions within conservation biology from the outset, but also drove the search for deeper consensus and innovation (Meine 2004). A Second International Conference on Conservation Biology convened at the University of Michigan in May 1985 (Soulé 1986). Prior to the meeting, the organizers formed two committees to consider establishing a new professional society and a new journal. A motion to organize the Society for Conservation Biology (SCB) was approved at the end of the meeting (Soulé 1987b). One of the Society’s first acts was to appoint David Ehrenfeld editor of the new journal Conservation Biology (Ehrenfeld 2000). The founding of SCB coincided with planning for the National Forum on BioDiversity, held September 21–24, 1986 in Washington, DC. The forum, broadcast via satellite to a national and international audience, was organized by the US National Academy of Sciences and the Smithsonian Institution. Although arranged independently of the process that led to SCB’s creation, the forum represented a convergence of conservation concern, scientific expertise, and interdisciplinary commitment.

In planning the event, Walter Rosen, a program officer with the National Research Council, began using a contracted form of the phrase biological diversity. The abridged form biodiversity began its etymological career. The forum’s proceedings were published as Biodiversity (Wilson and Peter 1988). The wide impact of the forum and the book assured that the landscape of conservation science, policy, and action would never be the same. For some, conservation biology appeared as a new, unproven, and unwelcome kid on the conservation block. Its adherents, however, saw it as the culmination of trends long latent within ecology and conservation, and as a necessary adaptation to new knowledge and a gathering crisis. Conservation biology quickly gained its footing within academia, zoos and botanical gardens, non-profit conservation groups, resource management agencies, and international development organizations (Soulé 1987b). In retrospect, the rapid growth of conservation biology reflected essential qualities that set it apart from predecessor and affiliated fields:

Conservation biology rests upon a scientific foundationin systematics, genetics, ecology, and evolutionary biology. As the Modern Synthesis rearranged the building blocks of biology, and new insights emerged from population genetics, developmental genetics (heritability studies), and island biogeography in the 1960s, the application of biology in conservation was bound to shift as well. This found expression in conservation biology’s primary focus on the conservation of genetic, species, and ecosystem diversity (rather than those ecosystem components with obvious or direct economic value).

Conservation biology paid attention to the entire biota; to diversity at all levels of biological organization; to patterns of diversity at various temporal and spatial scales; and to the evolutionary and ecological processes that maintain diversity. In particular, emerging insights from ecosystem ecology, disturbance ecology, and landscape ecology in the 1980s shifted the perspective of ecologists and conservationists, placing greater emphasis on the dynamic nature of ecosystems and landscapes (e.g. Pickett and White 1985; Forman 1995).

Conservation biology was an interdisciplinary, systems-oriented, and inclusive response to conservation dilemmas exacerbated by approaches that were too narrowly focused, fragmented, and exclusive (Soulé 1985; Noss and Cooperrider 1994). It provided an interdisciplinary home for those in established disciplines who sought new ways to organize and use scientific information, and who followed broader ethical imperatives. It also reached beyond its own core scientific disciplines to incorporate insights from the social sciences and humanities, from the empirical experience of resource managers, and from diverse cultural sources (Grumbine 1992; Knight and Bates 1995).

Conservation biology acknowledged its status as an inherently “value-laden” field. Soulé (1985) asserted that “ethical norms are a genuine part of conservation biology.” Noss (1999) regarded this as a distinguishing characteristic, noting an “overarching normative assumption in conservation biology. . . that biodiversity is good and ought to be preserved.” Leopold’s land ethic and related appeals to intergenerational responsibilities and the intrinsic value of non-human life motivated growing numbers of conservation scientists and environmental ethicists (Ehrenfeld 1981; Samson and Knopf 1982; Devall and Sessions 1985; Nash 1989). This explicit recognition of conservation biology’s ethical content stood in contrast to the usual avoidance of such considerations within the sciences historically (McIntosh 1980; Barbour 1995; Barry and Oelschlaeger 1996).

Conservation biology recognized a “close linkage” between biodiversity conservation and economic development and sought new ways to improve that relationship. As sustainability became the catch-all term for development that sought to blend environmental, social, and economic goals, conservation biology provided a new venue at the intersection of ecology, ethics, and economics (Daly and Cobb 1989). To achieve its goals, conservation biology had to reach beyond the sciences and generate conversations with economists, advocates, policy- makers, ethicists, educators, the private sector,and community-based conservationists.

Conservation biology thus emerged in response to both increasing knowledge and expanding demands. In harnessing that knowledge and meeting those demands, it offered a new, integrative, and interdisciplinary approach to conservation science.