Endangered Ecosystems
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ENDANGERED ECOSYSTEMS Raymond C. Nias and John R. Mooney WWF Australia I. Introduction to some degree adversely affected by human activities, II. Major Ecosystems at Risk with forests, scrub and grasslands, and freshwater and III. The Conservation of Ecosystems coastal ecosystems being the most threatened. Specific ecosystems at high risk include dry tropical forests, especially on islands, temperate forests, Mediterranean shrublands, temperate grasslands, and most coastal GLOSSARY marine systems. Overall, the large marine and oceanic ecosystems, polar regions, and dry deserts are gene- biological diversity The variety of genes, species, rally less threatened, although the potential impacts of and ecosystems in the living world. climate change on these ecosystems are only just biome Group of ecosystems with similar character- beginning to be understood. istics, usually a major vegetation type such as trop- ical rain forest or grassland. community All of the populations of different organ- I. INTRODUCTION isms that live within a given area. conservation status Relative likelihood of extinction A. Definition of an Endangered Ecosystem of a species or community. deforestation Physical removal of trees and conse- The Convention on Biological Diversity (CBD) 1992, quent reduction in forest cover. defines an ecosystem as ‘‘a dynamic complex of plant, ecoregion Geographic region of similar ecological animal and micro-organism communities and their non- processes and ecosystems. living environment interacting as a functional unit.’’ By ecosystem A dynamic complex of plant, animal, and itself, however, the term ‘‘ecosystem’’ does not define any microorganism communities and their nonliving specific dimensions and the boundaries of ecosystems environment interacting as a functional unit. are often indistinct. Even in aquatic ecosystems, where endangered Very likely to become extinct within the the presence of water helps to identify the boundaries of near future. lakes and rivers, the extent of an aquatic ecosystem endemism Degree to which species are unique to a fluctuates with changing water levels, floods, and tides. specific location. In the marine environment, ecosystems may be defined by particular attributes of water temperature or chem- istry, or by the characteristics of the substrate, in addi- tion to specific plant communities, such as sea grass THE SCALE OF HUMAN IMPACT on the natural beds or kelp forests. Other ecosystems may be defined environment has resulted in the decline and loss of by specific geographic or special physical characteristics, many ecosystems. All of the world’s major biomes are such as caves or seamounts. Encyclopedia of Biodiversity Copyright & 2007 Elsevier Inc. All rights of reproduction in any form reserved. 1 2 _________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ ENDANGERED ECOSYSTEMS_________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ The concept of an endangered ecosystem is The purpose of the Millennium Ecosystem Assess- relatively new as compared with the widely accepted ment (MA) as stated in the foreword to the Biodiversity concept of an endangered species. The World Cons- Synthesis report was to ‘‘assess the consequences of ervation Union (IUCN) has maintained an inter- ecosystem change for human well-being and to estab- nationally recognized system of Red Data Books lish the scientific basis for actions needed to enhance for defining and listing threatened species for many the conservation and sustainable use of ecosystems and years, but no universally applied system has been their contributions to human well-being.’’ The report developed for ecosystems so far. Similarly, there is no includes global overviews of major ecosystem types recognized system for measuring the relative cons- including marine systems, coastal systems, inland wa- ervation status of an ecosystem and it is often not clear ter systems, forest systems, dryland systems, island in what sense the whole of the ecosystem can be seen systems, mountain systems, and polar systems. In ad- to be threatened. While it is clear in most cases at what dition to these overviews, 18 subglobal assessments point a species has become extinct, it is much less were commissioned as part of the overall project. clear at what point a specific ecosystem ceases to exist. The conclusions of the MA are graphic in their The uncertainty in defining the exact extent of an portrayal of ecosystem loss and state that ‘‘virtually all ecosystem has hampered attempts to quantify their of Earth’s ecosystems have now been dramatically conservation status, and there is an ongoing debate as transformed through human actions.’’ In summary, to the appropriate scale for organizing and prioritizing over half of the 14 biomes that the MA assessed have conservation efforts. At the broadest level, ecosystems experienced a 20–50% conversion to human use, with cross international boundaries and are subject to a temperate and Mediterranean forests and temperate wide range of threats and human influences. These grasslands being the most affected. major ecosystem types can be subdivided, as they vary At the national level, both the United States and enormously in their biological composition, environ- Australia have undertaken recent reviews of threat- ment, and functioning, often as a result of major ened ecosystems. In Australia, some 2859 threatened geographic features such as mountain ranges, bays, ecosystems were identified in 2002, the majority of and river catchments. At a finer level, an ecosystem these being ecosystems associated with eucalypt forest may comprise a small group of underwater cave sys- and woodlands. tems, sand dunes, an isolated island and fringing coral reef, or a mossy high-altitude swamp that covers no more than a few hectares. II. MAJOR ECOSYSTEMS AT RISK A. Forests and Woodlands B. Global Reviews of Endangered Ecosystems The net reduction in global forest and woodland cover The paucity of information on many ecosystems, as is estimated to be 5.3 million ha/yr, with more than well as the lack of a standard approach, has hampered one-third converted globally since 1700, mostly as a past attempts at national or global assessments of result of expanding human populations and agricul- conservation status. However, recent progress in de- ture. Trends in deforestation and net changes in forest termining the conservation status of ecosystems at a area vary across regions, although there are many global level has been made in response to the iden- commonalities within major biomes across regions. In tified need for an international ecosystem assessment densely populated subregions, such as western Europe by a number of international agencies. Organizations and southern China, this level of conversion has been that have been involved in global reviews of threatened much greater, with o30% of original vegetation cover ecosystems include the United Nations Environment now remaining. Programme, and nongovernmental organizations such The large-scale loss of ecosystems resulting from as Conservation International (biodiversity hotspots) human influence has been most apparent in the and WWF (Global 200 ecoregions). The most signi- conversion of fertile temperate forests into cropland ficant of these have been published by the United Na- and pasture. Considerable decline in forest area had tions Environment Programme in the form of the already taken place by 1700, especially in the Medi- Global Environment Outlook series and The World terranean Basin and the Indus Valley and in northern Resource Institute’s Millennium Ecosystem Assessment and northwestern China. Large declines also occurred (Reid et al., 2005). in northwestern Europe during the Middle Ages. __________________________________________________________________________________________________________________________________________________________________________ ENDANGERED ECOSYSTEMS_______________________________________________________________________________________________________________________________________________________________________ 3 Primary or old growth forest (more than 200 years old) limited, but settlement and agriculture around roads is now only a small part of the world’s total forest area. built to transport timber have resulted in additional In contrast to the Mediterranean region, developm- clearing of forest areas. ent in North America did not lead to the almost com- In South America, deforestation is also mainly due plete loss of forest. Over some 150 years, an initial to the expansion of agriculture. This process is driven rapid conversion of forested land was followed by a by a number of factors, the most important being the slowing down in clearance rates, and eventually by displacement of peasant farmers from traditional far- stabilization. In Australia, some 47% of all forests were ming areas, large-scale settlement programs such as in cleared over the last 200 years, mostly during the pe- Rondoˆnia in Brazil, and the deliberate promotion of riod of rapid economic expansion and mechanized livestock-raising activities