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Twenty-​first-​century cli­mate changes are expected to have effect on the tree of life, as it is envis­aged that many species will become affected. If losses are not ran­domly dis­trib­uted across the tree of life, cli­mate change could lead to a dis­pro­por­tion­ate loss of evo­lu­tion­ary his­tory. How­ever, in Europe, cli­mate change will affect the dif­fer­ent plant and ani­mal groups (gen­era, fam­i­lies, orders) in about the same degree.

There are hardly any gen­era or fam­i­lies which are threat­ened in their entirety to go extinct. This keeps the so-​called ‘phy­lo­ge­netic diver­sity’ in Europe high. Researchers con­clude this in Nature this week, based on a sur­vey of the envi­ron­men­tal require­ments of 1280 Euro­pean plant species, 340 bird species and 140 mammals.

Phy­lo­ge­netic diver­sity is a mea­sure of bio­di­ver­sity, which was intro­duced in 1992 by Aus­tralian Daniel Faith. It is more sub­tle than a sim­ple species list and takes into account the degree of relat­ed­ness between plants or ani­mals. For exam­ple, when in a given area 25 unre­lated dif­fer­ent bird species breed, the bio­di­ver­sity is val­ued more highly than when there would have been 25 closely related endemic bird species.

The researchers deter­mined the rela­tion­ship between the hun­dreds of plants and ani­mals by DNA analy­sis. The envi­ron­men­tal require­ments (min­i­mum tem­per­a­ture, pre­cip­i­ta­tion, etc.) of the plant and ani­mal species were derived from their cur­rent dis­tri­b­u­tion. Then, for two emis­sion sce­nar­ios (includ­ing an extremely unfa­vor­able IPCC sce­nario) using known cli­mate mod­els it was deter­mined how the species’ geo­graph­i­cal dis­tri­b­u­tion would be changed in 2020, 2050 and 2080. This showed that species vul­ner­a­bil­ity to cli­mate change clus­ters weakly across phy­lo­ge­nies. The impact on bio­di­ver­sity, e.g. phy­lo­ge­netic extinc­tion, is not greater than when the cli­matic influ­ence had been totally ran­dom. This is because vul­ner­a­ble species have nei­ther fewer nor closer rel­a­tives than the remain­ing tax­o­nomic branches of the tree of life.

All in all Euro­pean bio­di­ver­sity loss will suf­fer far less dam­age than is sug­gested by researchers who used a sim­ple species lists. Reduc­tions in phy­lo­ge­netic diver­sity will be greater in south­ern Europe, and gains are expected in regions of high lat­i­tude or alti­tude. Unfor­tu­nately, losses will not be com­pen­sated by gains and the tree of life faces a trend towards homog­e­niza­tion across the con­ti­nent. (Sources, NRC, 19.02.2011; Nature, 16.02.2011)