Existing comment:
William F. Laurance (Smithsonian Tropical Research Institute)
Some of his slides:
Are We on the Verge of a Tropical Extinction Crisis?
Various authors have argued so:
- Key justification for new reserves and conservation initiatives
Dirzo & Raven 2003 suggest that:
- Only 5-10% of old-growth tropical forest will likely survive by 2050
- Perhaps 50-75% of all tropical species could become extinct or committed to extinction, based on species-area curves
Wright & Muller-Landau (2006a, 2006b): The Future of Tropical Forest Species
Seriously challenge idea of large-scale extinctions from habitat conversion.
Difficult to ignore:
- Prominent scientists
- Initially presented as right's ATBC presidential address
- Key conclusions were widely distributed in a press release
Responses to WML:
Brook et al (2006) Biotropica
Gardner et al (2007) Biotropica
Sloan (2007) Biotropica
Laurance (2007) Trends in Ecology & Evolution
Comments from referees:
- "Their argument is just plain dangerous... We should hit them hard--and with one voice."
- "I know you have to work with Wright, but you're being far too diplomatic and nice."
The WML Argument:
Strong relationship between net forest cover and population density -- especially rural density -- in tropical nations.
Population Growth in Developing Nations: *
(1) Growth is generally slowing.
(2) A strong urbanization trend is expected.
(3) Rural densities expected to plateau, at least in Latin America and tropical Asia
* based on median projection of UN Population Division.
Species-Area Relationship:
Population projections used to predict future forest cover for each nation.
Species-area relationship used to predict species losses for Asian, African, and American tropics
Key Predictions of WML:
Just 21-24% and 16-35% of all species will be threatened with extinction in the Asian and African tropics, respectively.
Extinctions will be even lower in Neotropics because more forest will survive
More Reasons for Limited Extinctions:
Endangered species do not disappear immediately
As rural populations decline, secondary forests should proliferate, buffering many species from extinction
Past extinction filters have already removed the most vulnerable species from ecosystems
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