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Global warming may cause animals to shrink

Sept 27, 2011
Courtesy of Queen Mary, University of London
and World Science staff

Glob­al warm­ing will cause many of the world’s or­gan­isms to shrink, ac­cord­ing to new re­search.

Sci­en­tists con­tend that al­most all cold-blood­ed or­gan­isms de­vel­op ac­cord­ing to a “tem­per­a­ture-size rule” that de­scribes how they reach a smaller adult size when reared at warm­er tem­per­a­tures. But un­til now, sci­en­tists have not fully un­der­stood how these size changes take place.

Writ­ing in the jour­nal The Amer­i­can Nat­u­ral­ist, An­drew Hirst and col­leagues from Queen Mary, Uni­vers­ity of Lon­don ex­plored the ef­fect in more de­tail, show­ing con­clu­sive­ly, they said, how it oc­curs.

The study was car­ried out us­ing da­ta on ma­rine plank­ton­ic cope­pods. These ti­ny crus­taceans are the main an­i­mal plank­ton in the world’s oceans and are im­por­tant graz­ers of smaller plank­ton and a food source for larg­er fish, birds and ma­rine mam­mals.

Gath­er­ing more than 40 years of re­search stu­dying the ef­fect of tem­per­a­ture on these or­gan­isms, the in­ves­ti­ga­tors showed that how fast an an­i­mal grows in size does­n’t nec­es­sarily match how fast it passes through its life stages. In other words, these processes can fol­low two sep­ar­ate tracks at two diff­er­ent speeds.

“Growth and de­vel­opment in­crease at dif­fer­ent rates as tem­per­a­tures war­m,” Hirst said. “The con­se­quenc­es are that at warm­er tem­per­a­tures a spe­cies grows faster but ma­tures even faster still, re­sult­ing in them achiev­ing a smaller adult size.”

The “de­cou­pling,” or separa­t­ion, “of these rates could have im­por­tant con­se­quenc­es for in­di­vid­ual spe­cies and ecosys­tems,” he added.

Most sci­en­tists agree that hu­mans are caus­ing glob­al warm­ing by burn­ing fos­sil fu­els that re­lease heat-trapping, or green­house, gas­es.

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Global warming will cause many of the world’s organisms to shrink, according to new research. Scientists contend that almost all cold-blooded organisms develop according to a “temperature-size rule” that describes how individuals of the same species reach a smaller adult size when reared at warmer temperatures. But until now, scientists have not fully understood how these size changes take place. Writing in the journal The American Naturalist, Andrew Hirst and colleagues from Queen Mary, University of London explored the effect in more detail, showing conclusively, they said, how it occurs. The study was carried out using data on marine planktonic copepods. These tiny crustaceans are the main animal plankton in the world’s oceans and are important grazers of smaller plankton and a food source for larger fish, birds and marine mammals. Gathering more than 40 years of research studying the effect of temperature on these organisms, the investigators showed that how fast an animal grows in size doesn’t necessarily match how fast it passes through its life stages. “Growth and development increase at different rates as temperatures warm,” Hirst said. “The consequences are that at warmer temperatures a species grows faster but matures even faster still, resulting in them achieving a smaller adult size.” The “decoupling,” or separation, “of these rates could have important consequences for individual species and ecosystems,” he added. Most scientists agree that humans are causing global warming by burning fossil fuels that release heat-trapping greenhouse gases.