This image, based on data from NASA’s MODIS instrument on the Terra satellite, shows Earth’s plant productivity in 2003. Regions of increased productivity are shown in green, with decreased productivity portrayed in red. Over the past 10 years, productivity has declined, reversing a trend.
More sobering environmental news, this time from a NASA release in advance of a scientific paper to be published in Science:
Earth has done an ecological about-face: Global plant productivity that once flourished under warming temperatures and a lengthened growing season is now on the decline, struck by the stress of drought.
The study, by NASA-funded researchers Maosheng Zhao and Steven Running of the University of Montana, found that the past 10 years have seen a decline in global plant productivity of 1 percent. That is slight, but it is also in stark contrast to the six percent increase experienced over the course of two earlier decades, according to the study.
The take-away message:
“These results are extraordinarily significant because they show that the global net effect of climatic warming on the productivity of terrestrial vegetation need not be positive — as was documented for the 1980’s and 1990’s,” said Diane Wickland, of NASA Headquarters and manager of NASA’s Terrestrial Ecology research program.
One Comment
The excellent paper of Zhaou and Running reaffirms that NPP is positively correlated with simultaneous warmth and wetness.
The difference between gross primary productivity (GPP) and NPP is the net amount of respiratory CO2 released into the atmosphere each year (and that amount is LARGE compared to the annual atmospheric increase in anthropogenically released CO2). Therefore, as fluctuations in surface temperature decrease, and/or dry the soil, NPP goes down.
However, for millenia, humans have been using irrigation – and warm-climate agriculture – to compensate for such vagaries of weather.
Such opportunities to engineer net CO2 sequestration, in the face of AGW, to end global warming, still persist.
See:
“Irrigated afforestation of the Sahara and Australian Outback to end global warming”
http://www.springerlink.com/openurl.asp?genre=article&id=doi:10.1007/s10584-009-9626-y