In a paper published in 2003, a University of Montana scientist showed that between 1982 and 1999, global terrestrial plant productivity increased by as much as six per cent, as climate change created conditions favourable to growth.

Maosheng Zhao and Steven Running of the same university set out to update that analysis by combining data from NASA’s Terra satellite with growing-season climate variables such as temperature, solar radiation and water.

They found that while longer growing seasons and warmer temperatures have continued to benefit high-latitude Northern Hemisphere ecosystems, in the south, warming-associated drought has limited growth. The net effect is that since 2000, productivity has declined by one per cent. ‘We see this as a bit of a surprise, and potentially significant on a policy level because previous interpretations suggested that global warming might actually help plant growth around the world,’ Running said.

‘The potential that future warming would cause additional declines doesn’t bode well for the ability of the biosphere to support multiple societal demands for agricultural production, fibre needs and, increasingly, biofuel production,’ Zhao added.

October 2010