Ecosystems and Human Well-Being Biodiversity Ecosystems and Human Well-Being: Biodiversity Synthesis ecosystemshumanw05kuma Year: 2005 120 100 60 40 20- with the majority of these areas in Asia (C22). A study of the southern African biota shows how degradation of habitats led to loss of biodiversity across all taxa. (See Figure ) Cultivated systems (defined in the MA to be areas in which at least 30 of the landscape is in croplands, shifting cultivation, confined livestock production, or freshwater aquaculture in any par- ticular year) cover 24 of Earth's surface. (See Figure ) In 1
Ecosystems and Human Well-Being Biodiversity Ecosystems and Human Well-Being: Biodiversity Synthesis ecosystemshumanw05kuma Year: 2005 120 100 60 40 20- with the majority of these areas in Asia (C22). A study of the southern African biota shows how degradation of habitats led to loss of biodiversity across all taxa. (See Figure ) Cultivated systems (defined in the MA to be areas in which at least 30 of the landscape is in croplands, shifting cultivation, confined livestock production, or freshwater aquaculture in any par- ticular year) cover 24 of Earth's surface. (See Figure ) In 1990, around 40 of the crop- land is located in Asia; Europe accounts for 16, and Africa, North America, and South America each account for 13 (S7). For marine ecosystems, the most important direct driver of change in the past 50 years, in the aggregate, has been fishing. Fishing is the major direct anthropogenic force affecting the structure, function, and biodiversity of the oceans (C18). Fishing pressure is so strong in some marine systems that over much of the world the biomass offish targeted in fisheries (including that of both the target species and those caught inci- dentally) has been reduced by 90 relative to lev- els prior to the onset of industrial fishing. In these areas a number of targeted stocks in all oceans have collapsed—having been overfished or fished above their maximum sustainable levels. Recent studies have demonstrated that global fisheries landings peaked in the late 1980s and are now declining despite increasing effort and fishing power, with little evidence of this trend reversing under current practices (CI ). In addition to the landings, the average trophic level of global landings is declining, which implies that we are increasingly relying on fish that originate from the lower part of marine food webs (). (See Figures and ) Destructive fishing is also a factor in shallower waters; bottom trawling homogenizes three-dimensional b
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