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Record-breaking 2010 Amazon drought seen from space

By Martin Leggett - 30 Mar 2011 12:28:0 GMT
Record-breaking 2010 Amazon drought seen from space

The verdancy of the Amazon's lush tropical forests visibly drained away, during last year's severe drought, according to satellite-image analysis from a NASA-funded study. And the view from space showed that the rain forests failed to bounce back again in the autumn, suggesting longer-term effects from this record-breaking drought.

The news of the browning of the Amazon basin was released yesterday, as a snapshot from a study of a decade's worth of data from 2 of NASA's orbiting satellites - known as MODIS (the Moderate Resolution Imaging Spectroradiometer) and TRMM (the Tropical Rainfall Measuring Mission. The team studying the data - drawn from expert fields across the globe - was attempting to assess the impact of climate change one of the planet's largest terrestrial stores of carbon.

They wanted to measure the drought sensitivity of the region, as climate models predict an increasingly dry time in the Amazon. The TRMM satellite helped them to map out areas where rainfall is low, and the MODIS images looked for two different levels of greenness - one to indicate the leaf area, and another to measure the how well trees were functioning under water stress.

NASA satellite sensors, such as MODIS, showed an average pattern of greenness of vegetation on South America: Amazon forests which have very high leaf area are shown in red and purple colors, the adjacent cerrado (savannas) which have lower leaf area are shown in shades of green, and the coastal deserts are shown in yellow colors.

Image Credit: Boston University/NASA

The drought of 2010 had levels of the Amazon's rivers falling below levels see on any historical records. And it was all the more worrying for following a supposed 'once in a century' drought in 2005. Many rivers dried up completely, and the Brazilian government had to put together an aid package, and supply airlifts, for afflicted communities.

The severity of the drought was clearly picked up by the study. Close to a million square km of vegetation showed reduced levels of greenness - four times the 2005 dry-out area.

One of the lead authors of the study, Arindam Samanta, said '' The MODIS vegetation greenness data suggest a more widespread, severe and long-lasting impact to Amazonian vegetation than what can be inferred based solely on rainfall data.''

The close association of two severe droughts, in the last decade, has many worried that global warming has hit the regional climate system. Both droughts were linked to unusually warm Atlantic sea temperatures, off of the east coast of Brazil. That is worrying on two levels.

Large amounts of carbon are currently locked in the vast biomass of the tropical rain forests, and so kept out of the atmosphere. Climate models suggest that decreased rains will turn the rain forest to savanna, devastating an incredibly diverse ecosystem - and also unleashing a torrent of CO2. The last thing we need is for Mother Nature to start increasing her CO2 emissions, as we struggle to cut ours.