1. Golden Toad Laboratory for Conservation, Monteverde Cloud Forest Preserve and Tropical Science Center, Santa Elena, Puntarenas 5655, Box 73, Costa Rica, Central America
2. Department of Biology, University of Miami, PO Box 249118, Coral Gables, Florida 33124-0421, USA

Correspondence to: J. Alan Pounds^1,2 Correspondence and requests for materials should be addressed to J.A.P.
(e-mail: Email: goldtoad@sol.racsa.co.cr).

Abstract

Recent warming has caused changes in species distribution and abundance^{1, 2, 3}, but the extent of the effects is unclear. Here we investigate whether such changes in highland forests at Monteverde, Costa Rica, are related to the increase in air temperatures that followed a step-like warming of tropical oceans in 1976 (refs4, 5). Twenty of 50 species of anurans (frogs and toads) in a 30-km² study area, including the locally endemic golden toad (Bufo periglenes), disappeared following synchronous population crashes in 1987 (refs 6–8). Our results indicate that these crashes probably belong to a constellation of demographic changes that have altered communities of birds, reptiles and amphibians in the area and are linked to recent warming. The changes are all associated with patterns of dry-season mist frequency, which is negatively correlated with sea surface temperatures in the equatorial Pacific and has declined dramatically since the mid-1970s. The biological and climatic patterns suggest that atmospheric warming has raised the average altitude at the base of the orographic cloud bank, as predicted by the lifting-cloud-base hypothesis⁹,¹⁰.