Delayed responses and extinction debt: an opportunity for the conservation of Chaco Serrano forest birds

Abstract

Land-use change is one of the main threats to biodiversity at the global level, and subtropical dry forests are not exempt from such a threat. Recent studies suggest that species can become extinct with a considerable time lag, even if no further habitat loss occurs. Hence, there may be an extinction debt, which poses a great challenge to conservation. Here, we analyzed the response of taxonomic and functional richness of forest and understory specialist birds to 30 years (data from 1989, 2004 and 2019) of land-cover and land-use changes in the Chaco Serrano forest of central Argentina. Our results showed the occurrence of extinction debt in both forest and understory specialist birds, with such debt being greater in forest specialist birds. Results for species trait debt were inconclusive. We also found evidence that birds are not equally sensitive to land-use change, indicating a species-specific response. We conclude that the current presence of some large native forest patches and an intermediate degree of isolation in the region might be prolonging the persistence of some bird species and traits. Moreover, ecological legacies can strongly affect the current species distribution pattern and the permanence of functional traits in fragmented landscapes. These findings should be considered in conservation planning.