If you think there is no question that reserves are great for wildlife, think again. Spain’s Doñana National Park is such a draw to poachers that there are fewer badgers inside the reserve than in the area just outside it, according to new research in the February issue of Conservation Biology.
“The story of badger conservation in Doñana is probably a very good example of what is going on with many other species and in most protected areas,” says author Eloy Revilla, then of the Consejo Superior de Investigaciones Cientificas in Seville, Spain, and now of the UFZ Centre for Environmental Research in Leipzig, Germany.
The problem is that although European reserves are nominally protected from hunting, the abundance of fearless game (deer and wild boars) attracts poachers who also kill non-game species incidentally. This could devastate badgers and other carnivores because they require large habitats and live at low densities. However, little is known about the net effect of reserves on carnivore conservation.
To learn how reserves affect the Eurasian badger, Revilla and his colleagues studied a population living in and around the 200-square-mile Doñana National Park in southwestern Spain. Because it lies between Europe and Africa and between the Atlantic Ocean and the Mediterranean Sea, Doñana is one of the most biologically diverse reserves in Europe. The badgers, which weigh about 15 pounds each and are nocturnal, are thought to be declining in the Mediterranean region.
Revilla and his colleagues studied the rates and causes of death in two groups of badgers in the reserve: one living near the edge and one living near the core. The researchers estimated badger abundance at the edge, core, and just outside of the reserve based on a 1992-1993 survey of carnivore tracks in the Doñana region. The researchers monitored deaths in 33 radio-tagged badgers from both the “edge” and “core” groups, as well as of untagged badgers both in and just outside the reserve.
During the course of the study, Revilla and his colleagues found 20 dead badgers. The most common cause of death was poaching, and 80% of the poached badgers were killed inside the reserve while the rest were killed within about one mile of the edge.
The researchers found that so far, the reserve has benefitted badgers: badger density in the core was 1.4 times higher than that just outside the reserve. However, the edge of the reserve was detrimental to badgers: badger density in the edge group was much lower than that outside the reserve. This negative “edge effect” extended as far as two miles into the reserve and reduced its effectiveness at conserving badgers by more than one third. In other words, if badger abundance at the edge were as high as that at the core, there would have been one third more badgers in the reserve.
This finding is disturbing in light of a 1999-2000 survey of badgers in the Doñana region. While badger density is stable outside the reserve, preliminary analysis suggests that it has declined in the reserve.
To help keep the negative edge effect from outweighing the positive core effect of the reserve, Revilla and his colleagues call for controlling poaching by, in part, implementing existing policies and educating the people living nearby.
Revilla’s co-authors are: Francisco Palomares and Miguel Delibes, both of the Consejo Superior de Investigaciones Cientificas in Seville, Spain.
Revilla, E., F. Palomares, and M. Delibes. 2001. Edge-core effects and the effectiveness of traditional reserves in conservation: Eurasian Badgers in Doñana National Park. Conservation Biology 15(1):148-158.
Eloy Revilla (firstname.lastname@example.org)