Study linking global warming and species extinction is suspect

The news media widely circulated the claim that one million species will become extinct by 2050 due to global warming. However, the study published in Nature looked only at 1,103 plant and animal species in five regions. It concluded that about 15 to 37 percent of the 1,103 species studied would become extinct.

The study does not support the conclusion that a million species will become extinct, says Iain Murray of the Competitive Enterprise Institute:

The sample size of 1,103 was too small, considering that researchers estimate there are anywhere from 2 million to 80 million species, with about 1.6 million species actually documented.

The sample species are not representative; they include 243 South African proteaceae (evergreen trees and shrubs), of which there are only 1,000 species on the earth.

The model used makes "a lot of steady state assumptions that lead it to the most pessimistic forecast," says Daniel B. Botkin, of the University of California at Santa Barbara, in the New York Times, "including the notion that things will stay as they are in terms of the ways animals migrate and respond to temperature change."

Moreover, the study uses the "species-area relationship" rule – that small habitats support fewer species. However, empirical evidence does not always support the rule, says Murray:

The entire Eastern United States has lost only one species of bird through deforestation.

Puerto Rico, with much less land area, lost 7 of 60 bird species through deforestation – but eventually saw an increase to 97 bird species.

Additionally, the assumption that global warming will destroy habitat doesn't hold; atmospheric increases in carbon dioxide have led to a six percent increase in vegetation, 42 percent of which occurred in the Amazon rain forests.

So far, there have been just over 1,000 documented species extinctions since 1600.

Sources: Iain Murray, Virtually Extinct, Competitive Enterprise Institute; James Gorman, Scientist Predict Widespread Extinction by Global Warming, January 8, 2004; based on Chris D. Thomas, et al., Extinction Risk from Climate Change, Nature, January 8, 2004.

For CEI text http://www.cei.org/gencon/019,03797.cfm
For NY Times text http://www.nytimes.com/2004/01/08/science/08CLIM.html

For Nature text http://www.nature.com/cgi-
taf/dynapage.taf?file=/nature/journal/v427/n6970/index.html

For more on Endangered Species
http://eteam.ncpa.org/policy/Wildlife_Issues/Endangered_Species/

For more on Global Warming Impacts and Responses
http://eteam.ncpa.org/policy/Global_Warming/Impacts_and_Responses/

FMF Policy Bulletin/ 20 January 2004