Over the past 100 years, the global average temperature has increased by approximately 0.6 degrees C and is projected to continue to rise at a rapid rate. Although species have responded to climatic changes throughout their evolutionary history, a primary concern for wild species and their ecosystems is this rapid rate of change. We gathered information on species and global warming from 143 studies for our meta-analyses. These analyses reveal a consistent temperature-related shift, or 'fingerprint', in species ranging from molluscs to mammals and from grasses to trees. Indeed, more than 80% of the species that show changes are shifting in the direction expected on the basis of known physiological constraints of species. Consequently, the balance of evidence from these studies strongly suggests that a significant impact of global warming is already discernible in animal and plant populations. The synergism of rapid temperature rise and other stresses, in particular habitat destruction, could easily disrupt the connectedness among species and lead to a reformulation of species communities, reflecting differential changes in species, and to numerous extirpations and possibly extinctions.

As the Earth warms, many species are likely to disappear, often because of changing disease dynamics. Here we show that a recent mass extinction associated with pathogen outbreaks is tied to global warming. Seventeen years ago, in the mountains of Costa Rica, the Monteverde harlequin frog (Atelopus sp.) vanished along with the golden toad (Bufo periglenes). An estimated 67% of the 110 or so species of Atelopus, which are endemic to the American tropics, have met the same fate, and a pathogenic chytrid fungus (Batrachochytrium dendrobatidis) is implicated. Analysing the timing of losses in relation to changes in sea surface and air temperatures, we conclude with 'very high confidence' (> 99%, following the Intergovernmental Panel on Climate Change, IPCC) that large-scale warming is a key factor in the disappearances. We propose that temperatures at many highland localities are shifting towards the growth optimum of Batrachochytrium, thus encouraging outbreaks. With climate change promoting infectious disease and eroding biodiversity, the urgency of reducing greenhouse-gas concentrations is now undeniable.

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 Monteverde, 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 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 Paci®c 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 .This hypothesis builds on evidence that rising sea surface temperatures (SSTs) have altered the climates of tropical mountains. Enhanced evaporation from warm ocean surfaces has generated large amounts of water vapour, and latent heat released as this moisture condenses has accelerated atmospheric warming 5 . Because vertical thermal pro®les have tended towards a moist adiabatic lapse rate, the decline in temperature with increasing elevation has diminished, amplifying the warming in the highlands relative to the lowlands 11±13 . Freezing heights have shifted upwards 11 , and glaciers on high tropical mountains are rapidly melting 14 . If temperature-dependent relative humidity surfaces, and thus cloudformation heights, have likewise shifted upwards 10 , organisms may be affected in various ways. Monteverde's stratus±stratocumulus bank, which forms as the trade winds meet the Caribbean slope of the Cordillera de Tilara Ân,¯ow upwards and cool adiabatically, in¯u-ences several key ecological processes. A lifting cloud base should alter regional hydrology by reducing critical dry-season inputs of mist (low-intensity windblown precipitation) and cloud water (non-precipitating droplets deposited onto vegetation) 15,16 .To examine climate trends, we have analysed patterns of precipitation, stream¯ow, air temperatures and SSTs. The rainfall and air-temperature data (collected by J.H.C.) are from leeward cloud forest (1,540 m; ,1 km west of the Monteverde Cloud Forest Preserve headquarters and ,3 km west of the continental divide). The weather station lies on the western boundary of our 30-ha study plot for anoline lizards, which overlaps a 40-ha plot for birds. Both plots lie within the 30-km 2 anuran study area. The stream-¯ow data (from the Costa Rican Electrical Institute) are for the Rõ Âo Can Äas at Lõ Âbano (300 m; ,23 km northwest of Monteverde). The SST data (from NOAA) are ...

We surveyed the population status of the Neotropical toad genus Atelopus, and document recent catastrophic declines that are more severe than previously reported for any amphibian genus. Of 113 species that have been described or are candidates for description, data indicate that in 42 species, population sizes have been reduced by at least half and only ten species have stable populations. The status of the remaining taxa is unknown. At least 30 species have been missing from all known localities for at least 8 yr and are feared extinct. Most of these species were last seen between 1984 and 1996. All species restricted to elevations of above 1000 m have declined and 75 percent have disappeared, while 58 percent of lowland species have declined and 38 percent have disappeared. Habitat loss was not related to declines once we controlled for the effects of elevation. In fact, 22 species that occur in protected areas have disappeared. The fungal disease Batrachochytrium dendrobatidis has been documented from nine species that have declined, and may explain declines in higher elevation species that occur in undisturbed habitats. Climate change may also play a role, but other potential factors such as environmental contamination, trade, and introduced species are unlikely to have affected more than a handful of species. Widespread declines and extinctions in Atelopus may reflect population changes in other Neotropical amphibians that are more difficult to survey, and the loss of this trophic group may have cascading effects on other species in tropical ecosystems. RESUMENExaminamos el estado poblacional de las ranas neotropicales del género Atelopus y documentamos disminuciones catastróficas recientes, las más drásticas señaladas para cualquier género de anfibios. De las 113 especies que han sido descritas o son candidatas para ser descritas, los datos poblacionales indican que en 42 especies, las poblaciones han sido reducidas por lo menos a la mitad y solamente diez especies tienen poblaciones estables. El estado de los taxa restantes es desconocido. Por lo menos 30 especies no han sido vistas en al menos ocho años de todas las localidades conocidas, y se teme que se hayan extinguido La mayoría de estas especies desaparecieron entre 1984 y 1996. Todas las especies con SPECIAL SECTION Declines and Extinctions of Atelopus 191rangos altitudinales de 1000 m o superiores han sufrido disminuciones poblacionales, el 75 por ciento de estas ha desaparecido del todo. El 58 por ciento de las especies de bajura han sufrido disminuciones, mientras que el 38 por ciento ha desaparecido del todo. La pérdida de hábitat, no fue relacionada con las disminuciones una vez que se controló el efecto de altura en los análisis. De hecho, unas 22 especies que tienen poblaciones dentro deáreas protegidas han desaparecido. El hongo quítrido Batrachochytrium dendrobatidis estuvo presente en nueve especies que han experimentado disminuciones y puede explicar desapariciones en especies que ocupan hábitats no perturbados a mayores elevac...

Al~tract: The endemic go/den toad (Bufo periglenes) was abundant in Costa Rtca's Monteverde Cloud Forest Preserve in April-May 1987 but afterwards disappeare~ along with local populations of the harlequin frog (Atelopus varius). We examine the possible relationship between these sudden declines and unusually warm, dry conditions in 198Z For our analyses of local weather pattern~ we define a 12-month (July-June) amphibian moisture-temperature cycle consisting of four period~. (1) late wet season; (2) transition into dry season; (3) dry season; and (4) post-dry-season (earlywet-season) recovery. The 1986The -1987 cycle was the only one on record (of20 analyzed) with abnormally low rainfall in all four period~ and temperature anomalies in 1987 reached record high~ Flow in local aquifer-fed streams during the dry season and post-dry-season recovery period reached a record low. This climate disturbanc¢ associated with the 1986-1987 El Nifio/Southern Oscillatior¢ was more severe than a similar event associated with the 1982-1983 El Nifi~ though this earlier oscillation was the strongest of the past century. Demographic data for one harlequin fro8 populatiorg gathered during these two climatic event~ support the hypothesis that in 1987, shortly before the population col-lapsea~ the frogs undenaent an unprecedented shift in distri-