Special Section: New Insights into the Tropical Biodiversity Crisis

For conservation biologists, the contemporary loss of tropical biodiversity is among the greatest of all concerns. Regarded as the biologically richest ecosystems on the planet, old-growth tropical forests are disappearing at an alarming pace––roughly 30–60 football fields per minute (approximately 8–15 million ha/year) in recent decades (Achard et al. 2002; FAO 2007; Grainger 2008). During the past half-century, numerous tropical nations, including many in West Africa, Southeast Asia, South Asia, Central America, and Oceania, among others, have suffered striking declines in forest cover (FAO 2007). Even the world’s greatest tropical forests, such as the Amazon and Congo Basin, are being rapidly altered (Laurance et al. 2001; Soares-Filho et al. 2006; Laporte et al. 2007). Largely as a result of such alarming forest disruption, some argue that contemporary rates of species extinction are likely to be orders of magnitude higher than natural baseline levels (Pimm et al. 1995; Brooks et al. 1999; Pimm & Raven 2000; Brook et al. 2003). Others suggest that, if forest loss continues apace, we could witness catastrophic species losses this century. For example, on the basis of their assumption that just 5–10% of old-growth tropical forests will survive by 2050, Dirzo and Raven (2003) suggest that 50–75% of all tropical species––a shocking figure––could be committed to eventual extinction. Although other projections are less dire, the idea of a “tropical extinction crisis” is now well entrenched in the lexicon of conservation science (e.g., Wilson & Peter 1988; Laurance 1999; Sodhi et al. 2007). Nevertheless, as highlighted by the papers in this special section, the on-the-ground realities are more complex and more nuanced than simple projections can convey. In fact, prevailing views about the magnitude of tropical species extinctions have recently been challenged (Wright & Muller-Landau 2006a, 2006b), generating a heated debate about the fate of tropical biodiversity (e.g., Brook et al. 2006; Barlow et al. 2007; Laurance 2007; Fearnside 2008; Bradshaw et al. 2009). In addition, the drivers of tropical deforestation have shifted in recent years (Rudel 2005), with potentially important implications for conservation strategies (Butler & Laurance 2008). Finally, potentially serious new threats to tropical biodiversity, such as climatic change, overhunting, and emerging pathogens, are growing in importance (Laurance & Peres 2006). By exploring such issues in detail, we hope to provide here a fuller and more accurate perspective on the causes of biodiversity loss in the tropics.