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Satellites reveal strain on Earth’s biological resources


By James Dacey at the AGU in San Francisco

NASA satellite images have revealed that the biosphere is being placed under increasing strain as rising population on a global scale is accompanied by increased consumption of crops and animals per capita. If population and consumption continue to grow at present rates then by 2050 more than half of the new plant material generated on Earth each year will be required for humans. These findings were presented on Tuesday by NASA scientists at the American Geophysical Union (AGU) Fall Meeting here in San Francisco.

Marc Imhoff of the NASA Goddard Space Flight Center presented the results of a global survey for 1995–2005. Using data from NASA’s AVHRR and MODIS satellites, Imhoff and his colleagues tracked the amount of plant material produced on Earth. These satellites scan the Earth at 600 km per second, monitoring the colour of light emitted from the surface. Light near the green part of the spectrum is taken to indicate the presence of vegetation. A MODIS image of some of North America is shown above (image courtesy of NASA).

To create a “currency” for natural consumables, the researchers considered plants and animals in terms of the amount of carbon that they draw from the atmosphere – referred to as “net primary-production (NPP) carbon”. They discovered that between 1995 and 2005 the amount of NPP carbon used for human consumption rose from 20% to 25% of the total generated on land.

“These images tell us very dramatically that we do need to look at what kind of impact human consumption rates have on the ability of the biosphere to generate the supply,” said Imhoff.

He believes that the need for more plant products will have big implications for land management. As more land is required for agriculture, planning authorities will be faced with difficult decisions as they try to protect important ecosystems, such as boreal forest.

Rama Nemani, another member of the NASA team, is keen to stress that it’s not the role of Earth-monitoring programmes to suggest what should be done with global land use. He believes, however, that the next generation of Earth-monitoring satellites will play a key role in informing these discussions. These will include NASA’s National Polar-Orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project and ESA’s Sentinel satellites.

Nemani told me that he would also like to see the creation of an international body to monitor global biodiversity, in the same way that the climate is assessed by the Intergovernmental Panel on Climate Change (IPCC).

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