The number of threatened species and the severity of their extinction risks are predicted to increase greatly over the next five decades, as human populations and incomes grow, according to a Review article in this week’s Nature Insight on biodiversity. However, proactive international efforts towards sustainable farming, reducing land clearance and protecting natural lands could preserve much of Earth’s remaining biodiversity.
David Tilman and colleagues focused their analysis on terrestrial mammals and birds in three of the world’s most biodiverse regions: southeast Asia, India and China; sub-Saharan Africa; and tropical South America. In each of these areas, rapid increases in wealth and human population density threaten tens of thousands of animal species with extinction.
The authors find that habitat loss and degradation pose the most frequent direct threats to terrestrial mammals and birds by decreasing the area that a species can occupy, and therefore its abundance. About 80% of all threatened terrestrial bird and mammal species are imperilled by agriculturally driven habitat loss. Hunting and other forms of direct mortality endanger 40-50% of all threatened birds and mammals.
Current conservation programmes have saved at least 31 bird species from extinction in the past century and prevented an estimated 20% of threatened vertebrates from moving closer to extinction, the authors report. Captive breeding and reintroduction programmes have also saved several species, including the Arabian oryx and the California condor, although policies and practices still need improvement. For example, lion populations in many parts of Africa have fallen to just 10% of their potential, largely as a result of increasing human pressures but also owing to poor infrastructure and inadequate management budgets in protected areas. The authors conclude that with forethought, planning and effective conservation policies, however, Earth has the potential to provide healthy diets for 10 billion people in 2060 as well as preserve viable habitats for most of its remaining species.