The Amazon rainforest is the source of one-fifth of all fresh water on the planet, it is also the lungs of the planet or a carbon sink. It is called that because it sucks up the global emissions of carbon dioxide from things like cars, planes and power stations to name just a few. The Amazon rain forests hydrological system plays a critical function in regulating the global and regional climate. Water condensation, evaporation, and transpiration over the Amazon are key drivers of the global atmospheric circulation, affecting precipitation across South America and much of the Northern Hemisphere.
From Climate Central:
Professor Fu of the University of Texas, and her colleagues say the water stored in the forest soil at the end of each wet season is all that the trees have to last them through the dry months. The longer that lasts – regardless of how wet the wet season was – the more stressed the trees become and the more susceptible they are to forest fires.
Findings from a recent study show that since 1979, the dry season in southern Amazonia has stretched about a week longer per decade.
They say the most likely explanation for the lengthening dry season in recent decades is human-caused greenhouse warming, which inhibits rainfall in two ways: It makes it harder for warm, dry air near the surface to rise and freely mix with cool, moist air above; and it blocks incursions by cold weather fronts from outside the tropics which could trigger rainfall.
The team says the IPCC’s climate models represent these processes poorly, which might explain why they project only a slightly longer Amazonian dry season.
The Amazon rainforest normally acts as a carbon sink, removing atmospheric carbon dioxide and storing it. But during a severe drought in 2005 it went into reverse, releasing 1 petagram of carbon (1 billion tons – about one-tenth of annual human emissions) to the atmosphere.
Fu and her colleagues estimate that if dry seasons continue to lengthen at just half the rate seen in recent decades, the 2005 Amazon drought could become the norm rather than the exception by the end of this century.
Recently, 2 droughts have raised alarm bells on the health of the Amazon. Not only is the forest susceptible to drought and has increased forest fires as a result the problem is being exacerbated by logging and ranching and other agricultural uses.A 2005 drought is estimated to have turned the rainforest from a net absorber of about two billion tonnes of carbon dioxide to an exporter of some five billion tonnes of carbon dioxide, which is almost as much as the 5.4 billion tonnes emitted annually by the US.
The 2005 drought:
Throughout 2005unusually high sea temperatures prevailed in the North Atlantic. These exceptionally warm waters also powered the most destructive hurricane season on record, which included Hurricane Katrina. In Amazonia, and especially its western and southern regions, the subsiding air from the Atlantic convection dried the forest, helping make the 2005 dry season the driest ever in many locations.
In 2010 the drought was more widespread and more intense than the earlier drought, with a far bigger impact on the growth and death of trees, which is why the scientists expect the overall release of carbon dioxide from dead and decaying organic matter to reach eight billion tonnes.
In normal years the forest absorbs nearly 2 billion tonnes of carbon dioxide. The drought caused a loss of more than 3 billion tonnes. The total impact of the drought - 5 billion extra tonnes of carbon dioxide in the atmosphere - exceeds the annual emissions of Europe and Japan combined.
RAINFOR, the sole research organization dedicated to examining the rainforests of the Amazon reports:
Without this “carbon sink” the world’s ability to lock up carbon will be reduced, compounding the effects of global warming.
Amazon Watch predicts:
As global temperatures rise, the Amazon could become caught in a potentially calamitous feedback loop. In this vicious cycle, warmer oceanic waters will continue to dry out the basin, which in turn will release more carbon into the atmosphere. Warmer temperatures and a dryer forest will also increase forest fires, emitting more carbon and driving the process.
In a February 2010 report[PP3] , the World Bank estimated that the "tipping point" for the Amazon could be approximately 20% deforestation. If reached, this threshold could trigger a dramatic die-back of the Amazon rainforest. With 17% to 18% of the Amazon already deforested, another similar amount degraded, forest fires running rampant, and global temperatures already on the rise, the Amazon ecosystem could face ecological collapse sooner than previously expected.
The World Bank report concludes: "There are four major, non-linear, positive-feedback responses to global warming with the potential to create major disruptions in global climate. These are the slowing of the North Atlantic Thermohaline Circulation, the breakup of the West Antarctic Ice Sheet, methane emissions from melting permafrost, and Amazon forest dieback. Of the four, only Amazon forest dieback can to some extent be mitigated by deliberate intervention at a global scale through the reduction in greenhouse gas emissions combined with efforts to avoid further deforestation."
There is an organization attempting to help
mitigate this disaster. IMO, we need more help in addition to this, but it is a worthwhile project if it can succeed.
The reduced emissions from deforestation and degradation (REDD) project seeks to introduce new financial mechanisms which assure financial sustainability for the conservation of natural protected areas, indigenous territories and productive forests.
The REDD scheme is simple. Make the carbon stored in the trees worth money, so farmers and timber companies have an economic incentive not to cut them down.
The clip below has a fascinating discussion on REDD.