Mapping climatic mechanisms likely to favour the emergence of novel communities

Climatic conditions are changing at different rates and in different directions(1,2), potentially causing the emergence of novel species assemblages(3). Here we identify areas where recent (1901-2013) changes in temperature and precipitation are likely to be producing novel species assemblages through three distinct mechanisms: emergence of novel climatic combinations(4,5), rapid displacement of climatic isoclines(1,2,6-8) and local divergences between temperature and precipitation vectors(1,2). Novel climates appear in the tropics, while displacement is faster at higher latitudes and divergence is high in the subtropics and mountainous regions. Globally, novel climate combinations so far are rare (3.4% of evaluated cells), mean displacement is 3.7 km decade(-1) and divergence is high (>60 degrees) for 67% of evaluated cells. Via at least one of the proposed mechanisms, novel species assemblages are likely to be forming in the North American Great Plains and temperate forests, Amazon, South American grasslands, Australia, boreal Asia and Africa. In these areas, temperature- and moisture-sensitive species may be affected by new climates emerging, differential biotic lags to rapidly changing climates or by being pulled in opposite directions along local spatial gradients. These results provide spatially explicit hypotheses about where and why novel communities are likely to emerge due to recent climate change.