Biological response to climate change on a tropical mountain

Recent warming has caused changes in species distribution and abundance(1-3), but the extent of the effects is unclear. Here we investigate whether such changes in highland forests at Monte-verde, costa rica, are related to the increase in air temperatures that followed a step-like warming of tropical oceans in 1976 (refs 4, 5). Twenty of 50 species of anurans (frogs and toads) in a 30-km(2) study area, including the locally endemic golden toad (Bufo periglenes), disappeared following synchronous population crashed 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 hypothesis(9,10).