This preview shows page 1. Sign up to view the full content.
Unformatted text preview: Is a Mass Extinction Currently Underway? Today's questions: I. How rapidly are species going extinct? II. Why are species going extinct? III. What are the key ecological and evolutionary issues in conservation biology? I. How rapidly are species going extinct? A. Data on recent extinctions 1. Since year 1000, ~1,000* bird species have gone 1 Si 1000 1 000* bi d i h extinct. This is x the normal (background) rate. *This is an extremely conservative estimate ... may have been 2,000 species extinguished in Polynesia alone, as a result of human colonization. 2. 122 amphibian species have gone extinct in the past 25 years; this is past 25 years; this is x the background rate x the background rate B. Data on projected extinctions: IUCN Redlist
3 levels of threatened status Critical 50% probability of extinction in 5 years or 2 generations; total population < 250; OR >20% decline in 2 years or >50% in last generation % d li i %i l i g Endangered 20% probability of extinction in 20 years or 10 generations; total populations < 2,500; OR >5% decline over the past 5 years or >10% over 2 generations >5% decline over the past 5 years or >10% over 2 generations Vulnerable 10% probability of extinction in 100 years; 10% b bili f i i i 100 total population < 10,000; OR >1% decline over the past 10 years % of known species threatened with extinction ( (critically endangered, endangered, or vulnerable) ... y g , g , ) groups with at least 90% of all known species evaluated Mammals p Amphibians Birds Gymnosperms IUCN reports on the total number of eukaryote h l b f k species threatened with extinction
1998: 10,553 2000: 11,046 2002: 11,167 2003: 12,259 2004: 15,042 2006: 16,117 2006 16 117 2007: 16,308 2008: 16,928 2009: 17,291 2010: 18,351 2011: 19,570 `98-'11: N t = N0 t = er Nt = N0 ert II. Why are species going extinct? From 16001950, most extinctions occurred on islands, due to introduced species and direct exploitation by humans Recent data on endangered species from Canada f C d Currently: What is the major problem for terrestrial species? Wh i h j bl f i l i ? Where is overexploitation still a major problem, and why? p j p , y Data on forest loss (UN FAO; 11/30/11) Deforestation losses average M ha/yr: 1990 2005 Deforestation losses average M ha/yr: 19902005 ____ ____Global net loss Notes _ _ 1990s M ha/yr M ha/yr in tropics 200005 M ha/yr = ~1/3 WA state /y / Total net losses over this interval = M ha (3.9 WAs) "Forest" defined at 10% cover Forest defined at 10% cover Habitat fragmentation 1. Why does habitat quality decline? 2. Genetically, what happens to populations that become geographically isolated in small fragments? Due to genetic and demographic problems, populations that are small and geographically isolated may be in an that are small and geographically isolated may be in an "extinction vortex." What drives the vortex? ...
View Full Document