Global Carbon Metabolism

Econintersect:  Vegetation absorbs about 1/3 of the carbon emissions according to measurements taken over the past several decades.  Some good news of this front is that middle and high latitudes of the northern hemisphere have shown an increase in carbon absorption in recent years.  Bad news comes from equatorial and southern hemisphere regions where droughts and land plant and tree destruction have reduced photosynthesis activity.  The really bad news is that the net for the planet is that carbon sequestering by land vegetation for the entire planet has been declining.  Click on graphic image for larger view of global vegetation map.The data has been obtained indirectly, so it must be expected that the findings could be subject to revisions in the future, either to show less of a problem or a greater affect.

Here are some further details from Scientific Computing:

Data from Terra’s Moderate Resolution Imaging Spectroradiometer (MODIS) have turned up evidence that climate change may have negative effects for ecosystems earlier than we thought, according to Maosheng Zhao, an ecologist at the University of Montana in Missoula.

For the past several decades, photosynthesis by land plants and trees has absorbed, or acted as a “sink,” for about one third of global carbon dioxide emissions, helping to slow the increase of the greenhouse gas in the atmosphere. But scientists have found that global carbon uptake by land plants is declining.

“This decreasing trend has very important implications for how much and how long humans should count on the carbon sink capacity of terrestrial ecosystems,” Zhao said.

To arrive at their finding, Zhao and colleagues analyzed MODIS data from 2000 to 2008. Directly measuring carbon dioxide from space is difficult, so scientists rely on sensors to measure the photosynthetic activity of plants. That activity can then be translated to an estimate of how much carbon dioxide the plants are absorbing.

“So far, MODIS is the best sensor we have for monitoring global vegetation dynamics,” Zhao said.

Source:  Scientific Computing