The spatial scale of conservation necessary to avoid species extinctions is one of the most vigorous debates in conservation biology. One approach holds that protecting sites should be the primary level for action on the ground, the other that conservation action targeting broader seascapes and landscapes is more important. We address this debate systematically by assessing the appropriate spatial scales of conservation for all 4,239 threatened mammals, birds, tortoises and turtles, and amphibians. We find that, in the short-to medium term, 20% of these species are dependent on conservation at single sites, 62% on multiple sites, 18% on both sites and sea-or landscape-scale efforts, and <1% on broadscale actions alone (where sites are variably sized units that are actually or could potentially be managed for conservation, and "broad scale" refers to seaor landscape-scale and is determined by the needs of the species in question). Calls for broad-scale conservation action have generally focused on terrestrial birds and mammals, and we confirm that a fifth and a tenth of these, respectively, require conservation action at the landscape scale. However, we also find that two-fifths of threatened freshwater turtles and one-fifth of threatened amphibians depend on broad-scale conservation action to address changes in freshwater processes. Furthermore, the overwhelming majority of threatened marine mammals, birds, and turtles require urgent conservation action at the seascape scale. Our key conclusion is that neither site-scale nor broad-scale approaches alone can prevent mass extinction. Although site protection should remain the cornerstone for almost all threatened species, we demonstrate that a substantial proportion and unexpected diversity of threatened species will be lost in the absence of urgent conservation interventions at the sea-or landscape scale.
Limited mapping of migrations hampers conservation
Conservation efforts should target the few remaining areas of the world that represent outstanding examples of ecological integrity and aim to restore ecological integrity to a much broader area of the world with intact habitat and minimal species loss while this is still possible. There have been many assessments of “intactness” in recent years but most of these use measures of anthropogenic impact at a site, rather than faunal intactness or ecological integrity. This paper makes the first assessment of faunal intactness for the global terrestrial land surface and assesses how many ecoregions have sites that could qualify as Key Biodiversity Areas (KBAs – sites contributing significantly to the global persistence of biodiversity) based on their outstanding ecological integrity (under KBA Criterion C). Three datasets are combined on species loss at sites to create a new spatially explicit map of numbers of species extirpated. Based on this map it is estimated that no more than 2.9% of the land surface can be considered to be faunally intact. Additionally, using habitat/density distribution data for 15 large mammals we also make an initial assessment of areas where mammal densities are reduced, showing a further decrease in surface area to 2.8% of the land surface that could be considered functionally intact. Only 11% of the functionally intact areas that were identified are included within existing protected areas, and only 4% within existing KBAs triggered by other criteria. Our findings show that the number of ecoregions that could qualify as Criterion C KBAs could potentially increase land area up to 20% if their faunal composition was restored with the reintroduction of 1–5 species. Hence, if all necessary requirements are met in order to reintroduce species and regain faunal integrity, this will increase ecological integrity across much of the area where human impacts are low (human footprint ≤4). Focusing restoration efforts in these areas could significantly increase the area of the planet with full ecological integrity.
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