The Global 200 : a representation Approach to Conserving the Earth’s Distinctive Ecoregions



Download 2.75 Mb.
Page6/32
Date01.02.2018
Size2.75 Mb.
#38107
1   2   3   4   5   6   7   8   9   ...   32

Low temperatures, low salinity, high plankton levels and correspondingly green color generally characterize Polar marine waters. Extensive ice is also typical of the polar ocean, both in terms of cover by sheets and in the form of drift ice and icebergs carried by polar currents. Ice provides important habitat in the form of breeding platforms from which seals breed and search for food. Polar bears in the Arctic, and penguins in the Antarctic, also rely on the ice for habitat. Species diversity is enhanced in the Polar seas by a system of warm water upwellings that create breaks in the ice. The corresponding open areas support numerous invertebrates, fish, sea birds, and marine mammals—the result of a broad based food chain.

The Weddell Sea and Peninsular Antarctica were identified as the most productive and diverse ecoregions of the Antarctic large marine ecosystem (Van Mieghen & Oye 1965, Knox 1989), while the Bering, Beaufort, & Chukchi Seas and Barents Sea ecoregions are arguably the two most diverse and productive Arctic marine ecosystems (USSR Academy of Sciences 1988, Reeves & Leatherwood 1994).


27. Temperate Shelf & Seas

The Temperate Shelf and Seas are highly productive regions of great biological importance, supporting resident as well as migratory species during various life cycle stages. The relative shallowness of these regions (the continental shelf extends to an average maximum depth of 150 meters) leads to warmer temperatures and seasonal stratification of the water column based on temperature. Seasonal variability, along with freshwater influxes from coastal streams and tidal action, contribute to very heterogeneous habitats and a corresopondingly high diversity of organisms: fish, invertebrates (productive benthic communities), marine mammals, and numerous marine bird species.


Some of the most productive marine ecosystems occur in the Grand Banks and New Zealand plus the Patagonia ecoregions. The South Australian coastal waters are remarkable for unusually high levels of endemism in invertebrates, in addition to the diverse marine mammal assemblage found there. Two of the world’s largest temperate estuaries, the Chesapeake and Delaware Bays and the Northeast Atlantic Shelf are elevated to the Global 200 due to their size, productivity, and habitat diversity. Two of the most distinctive enclosed temperate seas, the Mediterranean Sea and the Yellow and East China Seas, are recognized in the Global 200.
28. Temperate Upwelling

Important coastal upwelling areas occur along the West Coast of North America where the California Current moves southward. Along the Southwest coast of Africa the Benguela Current exhibits similar dynamics.


Temperate Upwelling regions are continental margins characterized by the consistent welling up of nutrient rich bottom waters to the surface. These regions are remarkably productive and are associated with large fisheries and correspondingly large populations of seabirds. Fish populations are generally enormous, schooling, and characterized by great amounts of biomass but relatively few species of small fish (e.g., the Peruvian anchovetta). The high productivity in Temperate Upwelling regions is based on large quantities of low diversity phytoplankton communities that support short, relatively uncomplicated food chains. Species diversity is variable and often includes species entrained from deep upwelled water. These regions are largely characterized by low precipitation, and adjacent terrestrial ecoregions are often arid.
29. Tropical Upwelling

Similar to Temperate Upwelling areas, Tropical Upwelling habitats are characterized by high productivity resulting from the upwelling of nutrient rich bottom waters. These regions are distinct from other tropical waters in that the bottom waters bring cool water and nutrients to the surface. Contrasted with the warm, highly saline, and nutrient poor waters typical of tropical marine ecosytems, Tropical Upwelling habitats support distinctive species and systems. The combination of high productivity and tropical climates produce unique communities that often support a high level of endemism as well as high levels of productivity. Large numbers of fish and sea birds are found here, as are a diversity of sea turtles and marine mammals.


The Humboldt Current along the West Coast of South America and the Canary Current along the West Coast of Africa bring rich nutrients to the sea surface where they support highly productive marine systems. In addition, important tropical upwelling and current areas occur in the Panama Bight ecoregions.
30. Tropical Coral

The greatest known species diversity of any marine ecosystem is found in coral reefs; their vertical growth and complexity provides numerous niches for different species to fill. In addition to the calcium carbonate structure that the diverse corals species provide, numerous species of attached sponges and algae help to give the reefs their form. Tropical Coral reefs are fragile and diverse habitats that exist in sunlit waters along continental and island margins, with diversity greatest near the Equator.


Southeast Asian seas support over 450 species of scleractinian corals, the western Indian Ocean around 200, and the Caribbean only 50 species (Vernon 1995). Variation in reef fish and non-coral invertebrate diversity follosw a similar biogeographic pattern (Lieske & Myers 1994, McAllister et al. 1994). Overall, the coral reef communities of Southeast Asian seas are the most diverse in the world, with the Sulu, Sulawesi, Banda, and Coral sea ecoregions being the most diverse on Earth (Vernon 1995, Lieske & Myers 1994). The largest barrier reef in the world is the Great Barrier Reef. Other world-class barrier reefs include the barrier reefs of New Caledonia, the Mesoamerican barrier reef, and the large barrier reefs of Fiji. The largest coral atoll complexes occur in the Maldive-Lakshadweep ecoregion of the central Indian Ocean and in Micronesia.
Conservation Status of Ecoregions
Among all terrestrial Global 200 ecoregions (142 in total), 75 ecoregions (53%) are considered critical or endangered, 39 ecoregions (27%) vulnerable, and 28 ecoregions (20%) relatively stable or intact (Table 1). Terrestrial ecoregion boundaries do not reflect the extensive habitat loss, fragmentation, and degradation that have occurred in many of the terrestrial ecoregions. In ecoregions that have been dramatically altered, characteristic species and communities survive only in the few remaining small blocks of habitat (e.g., Collar & Stuart 1988, Dinerstein et al. 1995). Among the terrestrial MHTs, ecoregions falling within the tropical and subtropical dry broadleaf forests, temperate grasslands, Mediterranean shrublands, and temperate broadleaf and mixed forests are the most threatened. Virtually all biotas on small islands are vulnerable or critical/endangered due, in large part, due to their limited habitat area and extreme sensitivity to anthropogenic disturbance and alien species (Raven 1988, Wilson 1988, 1992, WCMC 1992, Sujatnika et al. 1994, Brooks et al. 1997, Reaka-Kudla 1997). Island ecoregions are projected to experience a wave of extinctions over the next two decades given the fragility of island ecosystems, the sensitivity and endemicity of island species, and the severe threats native island biotas face worldwide.
Assessment of conservation status for freshwater ecoregions in North America and South America was based on existing regional analyses (Abell et al. 2000, Olson et al. 1999). In Africa and Europe, analyses currently underway (Thieme et al. in prep.) provided the basis for rankings presented here. In areas where no regional assessment has been undertaken, review of relevant literature facilitated decisions on the levels of threat faced by native biotas. Worldwide, freshwater organisms represent a disproportionate amount of endangered species; thus, it is not suprising that so many freshwater ecoregions received a critical rating in the assessment. In particular, seasonally flooded forests, cataracts, and freshwater communities in xeric areas, are endangered worldwide (Goulding et al. 1996, Abell et al. 2000, Olson et al. 1999). Moreover, most temperate freshwater biotas are threatened by invasion of exotics, pollution, dams, and habitat degradation. Of the 53 identified freshwater ecoregions 31 (58%) were deemed to be critical or endangered, 10 (19%) were assessed as vulnerable, and only 12 (23%) to be relatively stable.
Marine ecoregions have not been assessed as to their conservation status. In marine MHTs, upwelling areas are heavily overfished, enclosed seas are degraded, and coral reefs and mangroves are severely affected by habitat destruction, degradation, and overfishing around the world (Sherman et al. 1990, Suchanek 1994, Suchanek 1994, Kelleher et al. 1995, Bryant et al. 1995, Olson et al. 1996, Ormond et al. 1997).
Degree of Overlap of Terrestrial, Freshwater, and Marine Global 200 Ecoregions
The linkages among terrestrial, freshwater, and marine conservation are often overlooked.

Among the Global 200, thirty-three (23%) of the 143 terrestrial ecoregions overlap extensively with freshwater ecoregions (i.e., more than 50% of the original extent of the terrestrial ecoregion is covered by a freshwater unit). Thirty-four (23%) of the terrestrial ecoregions share at least 50% of their coastline with a marine ecoregion. And ten (6%) of the terrestrial ecoregions do both, overlapping extensively with a freshwater ecoregion and sharing at least 50% of their coastline with a marine ecoregion. The exceptional terrestrial ecoregions of this third group are the Madagascar dry forests, Congolian coastal forests, Greater Antilles moist forests, Pacific temperate rainforests of North America, Queensland tropical moist forests, southeastern Australia Eucalyptus-Acacia forests, New Caledonia moist forests, New Caledonia dry forests, New Guinea lowland forests, Sulawesi moist forests, Philippines moist forests, Northeast Borneo/Palawan moist forests, and Russian Far East temperate forests. Carefully designed conservation activities in these thirteen units could ultimately affect 39 ecoregions.


Applying the Global 200 as a Tool for Global Biodiversity Conservation
The Global 200 is designed to be an effective tool for (1) targeting distinctive biogeographic units of biodiversity and (2) promoting ecosystem-level representation at global scales. The Global 200 broadens the goals of conservation from a primary focus on preserving species diversity to an encompassing view of habitat diversity, ecological and evolutionary phenomena as well as adaptations of species to different environmental conditions around the world. In some cases, it also distinguishes representative ecoregions that are relatively more intact than other examples, highlighting the best opportunities for long-term conservation.
Like any effort to set priorities, the Global 200 cannot address all aspects of biodiversity conservation. The Global 200 does not explicitly target: large wilderness areas (e.g., forest frontiers - Bryant et al. 1997), functional values of keystone habitats (e.g., wetlands, coral reefs, gallery forests - Bryant et al. 1998), large-scale ecological phenomena, such as migrations of marine mammals, sea turtles, birds, or fish; intra-tropical migrations of bats, birds, and insects; widespread and dynamic pelagic ecosystems; hydrothermal vent communities; abyssal ecosystems; cave and groundwater ecosystems; species of special concern (e.g., tigers and rhinos at risk from trade in animal parts), or global ecosystem dynamics such as carbon sequestration. More detailed, fine-scale analyses are essential to identify important targets within ecoregions.

Matching the Challenge of Biodiversity Loss

One tactical concern of the Global 200 is that it is ambitious, and that by focusing on 238 ecoregions rather than on a handful of conservation units, we run the risk of placing less emphasis on the most diverse and distinct ecoregions. In response, we argue that the broad geographic reach of the Global 200 makes almost every nation on Earth a stakeholder in a global conservation strategy. From the global scale to regional and national-level conservation strategies, the Global 200 lends weight to shared priorities and provides a global perspective for lobbying efforts by local conservation groups. The Global 200 also can help major development agencies better recognize and mitigate the effects of projects that result in land use change, or forego development activities in particularly sensitive ecoregions. For these reasons we see the Global 200 as a map guiding conservation investments so that a comprehensive plan eventually can be achieved by the global conservation community and the world’s nations.


The widespread destruction of the Earth’s biodiversity occurring today must be matched by a response an order of magnitude greater than currently exists. Thus, the Global 200 provides a necessarily ambitious template for a global conservation strategy.

Acknowledgments

We thank the regional experts, biologists, and conservationists who contributed their time and knowledge to the conservation analyses that went into the Global 200. Jim Leape and Chris Hails have provided critical support for this effort. The staff of WWF contributed greatly to the regional assessments from which the map is derived. We wish to thank the staff of WWF’s Conservation Science Program for their contribution to the analysis and preparation of the Global 200, specifically Wes Wettengel, Emma Underwood, Eric Wikramanayake, Illanga Itoua, Colby Loucks, Taylor Ricketts, Steve Walters, Prashant Hedao, Robin Abell, Patrick Hurley, Tom Allnutt, Holly Strand, Jennifer, D’Amico, Meghan McKnight, Meseret Taye, Yumiko Kura, John Morrison, Karen Carney, George Powell, Jonathan Adams, Linda Farley, and Rodolfo Werner. James-Martin Jones and Ulli Lagler helped in innumerable ways to facilitate the completion of this project. We thank the staff of WWF-United States and the numerous staff from the WWF Network, including all of the national organizations, various field offices and programs, and associates, for their review and comments on earlier drafts. Carla Langeveld provided invaluable assistance in tracking down source material. Andrea Brunholzl improved this paper with her comments.


1   2   3   4   5   6   7   8   9   ...   32




The database is protected by copyright ©ininet.org 2022
send message

    Main page