Extinction debt of Hungarian reserves:: A historical perspective

We compiled species lists of the birds, reptiles and amphibians found in Hungarian reserves, and then used these to estimate the level of historical species richness using species-area relationships. The situation in the 18th century, before largescale land transformation, such as river regulations and drainages, could be approximately reconstructed. The species-area relationship was significant for all three classes. We estimated that 1 amphibian species, 4 reptile species, and 230 species of birds have become extinct in Hungary during the last two centuries. The latter seems unrealistic, so we evatuated extinctions in raptors (Fatconiformes) which was the best known taxon. According to our estimation, there should be 23 extinct species of raptors in Hungary. However, we found only 14 potential species, even when considering unlikely species. Therefore, we conclude that the present species richness pattern in the reserves may have not reached equilibrium for several taxa (tike birds), but probably has done so for others (amphibians and reptiles). Although, it would be desirable to extend the analysis to other taxa, this result indicates the existence of time-delayed species extinctions after habitat destruction, that is, an extinction debt. Currently, few studies have reported a timedelay effect from Europe. However, the results of this study suggest that an extinction debt may be important and should be considered when developing conservation strategies. (c) 2006 Gesellschaft fur Okologie. Published by Elsevier GmbH. All rights reserved.