Reply from L. Hughes

Abstract

Two of the most basic observations in ecology are that species distributions are frequently determined by climate, and that year-to-year fluctuations in abundance and phenology are often correlated with climatic fluctuations. Forchhammer and Post1xClimatic signatures in ecology. Forchhammer, M.C. and Post, E. Trends Ecol. Evol. 2000; 15: 286Abstract | Full Text | Full Text PDF | PubMedSee all References emphasize that any influence of human-induced climate change will interact with natural cycles. They also correctly point out that at least some of the recent trends in population dynamics and phenology, purported to be evidence for the influence of human-induced climate change, might be caused by natural climate variation. Indeed, this was one of the caveats that I noted2xBiological consequences of global warming: is the signal already apparent?. Hughes, L. Trends Ecol. Evol. 2000; 15: 56–61Abstract | Full Text | Full Text PDF | PubMed | Scopus (1038)See all References should be kept in mind when interpreting recently published studies on the detection of anthropogenic climate change effects on biological systems. The relative roles of natural climate dynamics and of the enhanced greenhouse effect will no doubt be best understood with hindsight, several decades from now.In the meantime, we know that there has been an unequivocal increase in greenhouse gases over the past 150 years3xInterannual extremes in the rate of rise of atmospheric carbon dioxide since 1980. Keeling, C.D. et al. Nature. 1995; 375: 666–670Crossref | Scopus (872)See all References and that temperature increases have been recorded on a millennial, not just decadal, timescale4xNorthern hemisphere temperatures during the past millennium: inferences, uncertainties and limitations. Mann, M.E. et al. Geophys. Res. Lett. 1999; 26: 759–762Crossref | Scopus (1127)See all References. Along with this, rainfall patterns appear to be changing, glaciers are melting faster and sea levels are rising at rates consistent with thermal expansion (see studies cited in Ref. 2xBiological consequences of global warming: is the signal already apparent?. Hughes, L. Trends Ecol. Evol. 2000; 15: 56–61Abstract | Full Text | Full Text PDF | PubMed | Scopus (1038)See all ReferencesRef. 2). In the future, the response of natural systems to human-induced climate change will be complex and will interact with natural climatic variation at many scales. The effects of these interactions on communities as we know them may be profound5xSome Like it Hot: Climate Change, Biodiversity and the Survival of Species. Dudley, N. and Stolton, S. See all References, 6xEffects of climate change on biodiversity: a review and identification of key research issues. Kappelle, M. et al. Biodiv. Conserv. 1999; 8: 1383–1397Crossref | Scopus (69)See all References.In the face of these directional physical changes in the earth’s climate and geography, and the potentially devastating effect they might have on global biodiversity, we have to ask a new question. Should human-induced change still be considered an explanation of last resort – a hypothesis only to be taken seriously when all other possible explanations have been discounted?