a consensus that current extinction rates vastly exceed background ones, perhaps by two to three orders of magnitude (Pimm et al., 1995; Woodruff, 2001).
Although species loss occupies an overwhelming proportion of the literature, genetically distinct populations are also an important component of biodiversity. Estimates of population diversity and extinction rates are even more uncertain than those for species, but even these crude estimates are alarming: of perhaps 1 to 7 billion populations worldwide, 16 million may be extinguished each year in tropical forests alone (Hughes et al., 1997). Trends in key parameters of well-studied populations are consistent with this picture of decline. Amphibian populations have declined locally and globally in recent years (Houlahan et al., 2000; Rachowicz et al., 2006), and many mammal species worldwide exhibit range-size contractions indicative of heavy population loss (Ceballos and Ehrlich, 2002).
When we were first asked to prepare a paper addressing the question “Where does biodiversity go from here?” a variety of cynical answers leapt to mind. The principal threats to biodiversity—direct overexploitation of organisms, habitat destruction and degradation, environmental toxification, climate change, and biological invasions, among others—have been known for decades. Yet despite a ballooning number of publications about biodiversity and its plight, there has been dispiritingly little progress in stanching the losses—so little that some commentators have characterized applied ecology as “an evermore sophisticated refinement of the obituary of nature” (Jackson, 2007). As conservation-oriented scientists, we are responsible for biodiversity. Its loss is our failure.
We draw on the literature to sketch a brief and incomplete answer to the question posed to us, assuming that society continues business as usual. Because that outlook is bleaker than we are willing to accept, we then outline a more hopeful set of answers. These amount to a portfolio of strategies for combating biodiversity loss.
There are ≈6.7 billion people in the world as we write this, a number that is projected to grow (according to a mid-range forecast) to 9.3 billion by 2050 (Population Reference Bureau, 2007). The continued growth of the human population displaces biodiversity directly, as land is developed to create living room. In one recent example, Venezuelan president Hugo Chavez aims to translocate 100,000 people into a brand new city in El Avila National Park to alleviate overcrowding in Caracas (Forero, 2007). Providing a huge global populace with the resources necessary for survival (much less comfort) also displaces biodiversity. A recent spatially explicit