Modeled climate and land-use change threatens plant species

Study of South Africa’s proteas points to growing risks of extinction

Proteas–plants with large, colorful flowers that are important in the floral trade–are under threat from land-use change and climate change. A study based on a multispecies modeling effort for over 300 proteas of the Cape Floristic Region of South Africa suggests that the protected range of proteas is expected to decrease by 36 to 60 percent by 2050 as a result of climate change.

Proteas are a defining element of the renowned fynbos flora of the Cape biodiversity hotspot. The modeling work suggests that the risk of extinction for most protea species is likely to increase. Although as much as twenty percent of the land in the Cape Floristic Region is protected to some degree, land-use change alone can be expected to increase the number of threatened proteas in 2020 by between 4 and 13. When likely climate change is considered too, that number almost triples. Plausible assumptions lead to the conclusion that up to 15 percent of protea species will lose all representation in protected areas by 2050 because of expected climate change, and some will lose their range entirely, making extinction in the wild hard to avoid. The study, by Lee Hannah of Conservation International and three coauthors, is described in the March 2005 issue of BioScience, the monthly journal of the American Institute of Biological Sciences (AIBS).

Warming trends have been observed in the Cape region over the past 30 years, and the fate of protected areas there can offer lessons to inform conservation efforts throughout the world. The study by Hannah and colleagues is notable because it uses fine-scale modeling to assess predicted effects of both land-use change and climate change. Because the species studied are endemic to the Cape, the climate range acceptable to each species can be accurately characterized. Although the ranges of most protea species are expected to decrease as a result of climate change, those of a few species could expand. Hannah and colleagues point out, however, that their study does not attempt to evaluate some effects–such as the increasing prevalence of invasive species–that could compound the threats.