Landscape Ecology

A Top Down Approach

James Sanderson, James Sanderson

• Publisher: CRC Press
• Year: 2020
• ISBN:
  9780429525315
• Edition: 1
• Topic: Architektur
• Subtopic: Stadtplanung & Landschaftsgestaltung

Landscape Ecology - a rapidly growing science - quantifies the ways ecosystems interact. It establishes links between activities in one region and repercussions in another. Landscape Ecology: A Top-Down Approach serves as a general introduction to this emerging area of study.
In this book the authors take a "top down" approach. They believe that

Part I

The Presence of the Past

1

Brief History of Landscape Ecology

Jim Sanderson and Larry D. Harris

CONTENTS

Crisis in Conservation

Allerton Park

The Eternal External Threat

A Top-Down Approach

Conservation of Biotic Processes

A Note on Scale

The 1949 publication of what is affectionately referred to as “The Great APPES” (i.e., Principles of Animal Ecology, by Allee et al.), the close followup by Adrewartha and Birch (1954), as well as the magnum opus of field zoogeographer, Darlington (1957), brought the era of descriptive field ecology and matters of distribution and abundance of species to an honorable close, at least in The United States. The era of laboratory, experimental, and mathematical ecology quickly filled any existing niche space as by 1962 Preston (1962a, 1962b) and the immediacy of MacArthur and Wilson’s seminal work in 1963 initiated a new era for ecological thinking. Those of us sufficiently old to remember the popular press can wax “oh’ so” eloquently about how ‘ecology had now come of age.’ It is easily arguable that there had been a major paradigm shift in Kuhn’s (1962) sense of the concept.

A second happening involved the formal establishment of expensive, large-scale investigations under the aegis of The International Biome Program (IBP). These large scale, but all too descriptive research programs are epitomized in North America by the Grassland Biome Program centered at Ft. Collins, Colorado, and the Eastern Deciduous Forest Biome program centered at Oak Ridge National Laboratory in Tennessee (Golley 1993).

Although now the subject of too much ridicule, these grand and formalized, research programs led quickly to establishment of three Systems Ecology capacity-building grants that married the disciplines of mathematics, systems science, and ecology. Professor Frederick Smith, then at the University of Michigan, was not only central to the transformation just described, but he made yet one other, perhaps final, tactical maneuver. The world renowned Harvard Graduate School of Design and appropriate administrators recognized the need to bring formal ecological thinking into landscape architecture and regional planning programs; Professor Smith accepted stewardship of what was arguably the first official landscape ecology chair at a major university in the U.S. Other universities quickly followed in spirit, if not quite as formally.

At the Oak Ridge National Laboratory, the transition from systems ecology, as it had been conceived and executed in the Biome program transformed rather seamlessly into initiatives in what is now referred to as landscape ecology. Indeed, the explicit statements of this (as occurring in grant proposals and personnel recruitment) became obvious by the early 1970s. Their programming efforts led to a compilation of publications (Burgess and Sharpe 1981) that effectively melded the great descriptive data bases of the first half century of forest ecology in the eastern U.S. with the ongoing, but now dwindling, U.S. IBP research programs with the IBT paradigm which had captured a lot of attention by the mid to late 1970s. Even though descriptive field ecology found or created effective new niches (e.g., Organization for Tropical Studies, OTS), primarily in the tropics, the TIB and/or the ‘patch-in-a-matrix’ concept (Islands in the Stream?) had seemingly captured the budding research programs in landscape-level ecology.

Continental reserves surrounded by unnatural landscapes, for instance, became island reserves (Diamond 1975; Diamond and May 1976). Diamond (1975) argued that island biogeography results could be applied to the design of landlocked forested nature reserves and isolated mountain tops, so-called virtual islands (Diamond and May 1976). Maximum area and minimum perimeter, Diamond suggested, were critically important variables in reserve design, and the restoration of corridors that interconnected now dismembered landscapes, he argued (as Preston had said in 1962), could act to increase species persistence by increasing the effective area. Some of the successors of certain U.S. IBP groups pursued the tangent of watersheds as the next most promising endeavor. They chuckled when asked why not study wolf sheds, and it is reasonable to conclude that they had missed the point. But most importantly, the ecosystem, paradigm, and all that it stood for persisted in guiding conventional ecological research. A branch of ecologists, we refer to as community ecologists, aggregated with other sympathetic forces of biodiversity conservation to form a new organization: The Society for Conservation Biology. Needless to say, the ecosystem paradigm necessitated a focus on energy flow, trophic food webs, nutrient cycles, etc. Interactions between components of the systems were investigated almost mechanically, and output variables such as productivity, measured in units of gm/m2/yr, became a currency of ecosystem ecology. Although interactions within ecosystems were studied through time, major advances were made toward linking the biotic and abiotic components via the soil, to leaf, herbivore, carnivore, and decomposition (spatial heterogeneity was largely relegated to a different agenda). The study of species and the physical and chemical processes of their environment could now be taught like any other engineering discipline cookbook style. Though Golley as Division Director of Environmental Biology at the National Science Foundation from 1979 to 1981 asserted that humans be included in these study systems (as they were in Europe), momentum carried the ecosystem paradigm forward without them.

While debates such as those on reserve design (Single Large vs. Several Small — SLOSS) diverted attention from more pressing issues (Diamond 1975; Terborgh 1976; Simberloff and Abele 1976), Kushlan (1979), working in Everglades National Park in Florida, argued that the Theory of Island Biogeography did not quite apply as was assumed. The shifting pattern of population changes in 16 species of ciconiiform wading birds species indicated that the application of island biogeographic theory to the design and management of continental wildlife reserves required more consideration. Isolation of a continental reserve could lead to ecosystem degeneration, the extent and rapidity of which depended on the ecological condition of adjacent habitat. Here we find the profound significance of Kushlan’s results — the recognition that the contents of a protected area could be negatively impacted by the contextual setting of the area. Conflicts between species management and ecosystem management illustrated the need for a regional basis for preservation.

Kushlan (1979) realized that size alone was an inadequate measure of the effectiveness of a reserve. Everglades National Park was 5670 km²; it was bounded by Big Cypress National Preserve of 2370 km² and three Water Conservation Areas totaling 3490 km², making the total protected area about 12,000 km². The importance of environmental heterogeneity and maintenance of the functional characteristics of the reserve, such as the timing of changes in water levels beyond the park boundary, had to be considered. Spatial isolation from the buffering of contiguous habitats had resulted in quantitative and qualitative alteration of the functional relations within the reserve that led to environmental degradation and the decline in wading bird populations. Because local extirpations might occur in highly specialized species, Kushlan recommended a regional approach to the management and perpetuation of biodiversity that would permit recolonization from refugia when conditions changed. Environmental heterogeneity at the scale of the landscape was critical to maintaining biodiversity, especially in managed landscapes.

Crisis in Conservation

In 1980, Soulé and Wilcox sounded the alarm in the U.S. Whatever ecologists were doing was not working. In 1973, the 95th U.S. Congress amended the Endangered Species Act establishing, among other things, a legal mechanism known as “taking” for causing harm to a protected species. Ehrlich (1980), in the final chapter of Soulé and Wilcox (1980), claimed that the momentum of human exploitation of natural resources was likely to overwhelm the biosphere. He warned that for every hard-won battle, the forces of conservation “suffer crushing, if unheralded, defeats as unknown populations and species are plowed under from Anaheim to the Amazon.” Unless the trends of the past were suddenly and decisively reversed, conservationists could only hope to “slightly delay an unhappy end to the biotic Armageddon now underway.” Ehrlich and Ehrlich followed in 1981 with their book, Extinction.

Because years of field research and data collection were necessary to produce valuable results in ecological studies, the momentum built into scientific inquiry could not suddenly be terminated and redirected. Lovejoy et al. (1983, 1984) studied isolated forest tracts in Amazonia and argued that the results of MacArthur and Wilson applied. Harris (1984) wrote of fragmented forests in the northwestern U.S. and referred to island biogeographic theory in his book, The Fragmented Forrest. That terrestrial reserves were not habitat islands was clear to these authors. However, Harris wrote that “the whole module should be programmed into the context of a production-oriented landscape. This allows the preservation areas to be buffered from the harsh impacts and vicissitudes of the human-dominated landscape.”

Europeans, quite independently from the U.S., were pursuing their interests in the ecology of landscapes. The Netherlands Society for Landscape Ecology (NSLE) organized a conference in Veldhoven, The Netherlands, on April 6–11, 1981 (Tjallingii and de Veer 1982). NSLE was founded in 1972 “to gain a deeper understanding of the structure and functioning of landscapes and the patterns and processes in landscapes” (Wijnhoven 1982). Americans Julian Fabos, Richard Forman, Frank Golley, and Richard Sharpe attended. Through a series of lectures, workshops, and posters, Europeans presented their vision of landscape ecology. Most presentations addressed the negative impacts humans had upon the European landscape. Though aesthetics and architecture were integral components of European landscape ecology, van der Maarel (1982) wrote of the far-reaching side effects that humans had on nature reserves. “This makes nature reserves rather different from islands in the sea. Thus from a landscape-ecological point-of-view we must again further modify the theory of island biogeography.” He suggested that “landscape ecological theory” should play a major role in planning nature reserves.

Forman spent 1982 with Godron at the Centre d’Etudes Phytosociologiques et Ecologiques L. Embarger in Montpellier, France. At the Veldhoven conference, Forman (1982) presented his preliminary vision of landscape ecology. There he espoused the necessity of a contextual analysis of landscapes. A landscape, Forman suggested, was a matrix with patches and corridors where interactions occurred. Though he did not use the word “context” he referred to “specific linkages that exist with surrounding landscape elements” that must be considered when “making land-use decisions.” Theme IV of Veldhoven was devoted to the conservation of natural areas. The species, reserve, and resource-oriented approaches to conservation were all discussed, yet the work of Soulé and Wilcox was not referenced by a single speaker. In his closing remarks, Zonneveld as Chairman of the Congress Organizing Committee stressed the importance of the formation of an international society for landscape ecology. A year later Naveh (1982) explained that landscape ecology had gained a general recognition as a branch of modern ecology in central and eastern Europe and Israel. He used as examples the chairs in landscape ecology at several universities in Germany. “The Englishspeaking world, and especially the United States, is almost totally unaware of these developments,” he wrote. He attempted to spell out the theory and general principles Forman sought.

While papers and books fueled by the Theory of Island Biogeography continued to pile up and IBP research results flooded the American ecological literature, Forman convinced Paul Risser, then Chief of the Illinois Natural History Survey, and ecologist Jim Karr to host a meeting to discuss a new approach to research in ecology. Neither Risser nor Karr had experience in landscape ecology. The meeting was by invitation only and was strongly influenced by the IBP ecologists because no one in attendance, aside from Forman, Godron, and Golley, had more than a cursory knowledge of landscape ecology. The now historic meeting took place at Allerton, Illinois.

Allerton Park

On April 25–27, 1983, 25 attendees met at Allerton Park to discuss the foundation of a new synthetic discipline referred to as “regional ecology” or “landscape ecology.” Previous attempts to achieve a synthesis had failed, they claimed. A persistent nagging recognition prevailed throughout the meeting — either a new discipline or area of specialization would emerge alive and vibrant or be stillborn and forgotten. Given the historical background, Forman and Golley were probably determined to push through a “new” science of landscape ecology. The problem was convincing the rest of the invitees that this was the right thing to do. The ideas discussed were not new and had been presented in the European literature over the preceding decade. The time had arrived to collectively discuss landscape perspectives in basic and applied research on natural resources that, according to Risser et al. (1984), were “stalled by several converging themes” such as:

1. a preoccupation with the extension of island biogeography theory to continental landscape patches;

2. the presumption that ecosystem-level characteristics were adequate to address landscape-level characteristics;

3. a recognition of the need to address landscape issues in land and resource management;

4. a belief that map-overlay methodology was sufficient to capture the essential attributes of multiunit landscapes;

5. the realization that human activities were an integral part of any meaningful concept of landscape ecology; and

6. the recognition that the inclusion of many appropriate scientific disciplines results in an exceedingly complex field.

Although a landscape perspective in ecology was not new (Leopold 1949; Neff 1967; Troll 1968; Naveh 1982; Tjallingii and de Veer 1982), a firm theoretical basis for an ecology of landscapes was missing. Several authors (Forman 1982; Hansson 1977; Naveh 1982; Naveh and Lieberman 1984) were attempting to generalize ecology to guide research management, but without a definitive, ecologically based theory and methodology how could natural resources be managed?

Attendees “agreed” that landscape ecology should consider the development and dynamics of spatial heterogeneity, spatial and temporal interactions and exchanges across heterogeneous landscapes, influences of spatial heterogeneity on biotic and abiotic processes, and management of spatial heterogeneity. In 1984, the primary focus of landscape ecology was on:

1. spatially heterogeneous areas such as pine barrens (Forman 1979) and regions of row crop agriculture, Mediterranean woodland landscapes, and areas of urban and suburban landscapes;

2. fluxes or redistribution among landscape elements; and

3. human actions as responses to, and influences on, ecological processes.

The relationship between spatial pattern and ecological processes was not restricted to a particular scale. For instance, Weins (1985) discussed how organisms reacted to patterns in th...