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Rainforest canopy in the late afternoon. (Photo by R. Butler)
GLOBAL CONSEQUENCES
Tropical rainforests play a vital role in the functioning of the planet's natural systems. The forests regulate
local and global weather through their absorption and creation of rainfall and their exchange of atmospheric gases.
For example, the Amazon alone creates 50-80 percent of its own rainfall through transpiration. Cutting the rainforests
changes the reflectivity of the earth's surface, which affects global weather by altering wind and ocean current
patterns, and changes rainfall distribution. If the forests continue to be destroyed, global weather patterns may
become more unstable and extreme.
CLIMATIC ROLE OF FORESTS
As previously discussed, tropical rainforests play a vital role in local climate regulation by their interaction
with water cycles. However, rainforests also have a significant effect on global weather. Rainforests, like all
forms of vegetation, affect the "surface albedo" or reflectivity of a surface by absorbing more heat than bare soil. Norman Myers (1997) explains,
Much of the energy that converts surface moisture into water vapor comes
from the sun's radiational heating of the land surface. The energy thus depends on surface albedo, or relevant
degree of reflectant "shininess" of the land surface (Gash and Shuttleworth 1992). In turn, the albedo
depends on the vegetation, which absorbs more heat than does bare soil. Over thick vegetation, vigorous thermal
currents take moisture (provided by the same plant cover) up into the atmosphere, where it condenses as rain. Because
of its influence on convection patterns and wind currents, and hence on rainfall regimes, the albedo effect constitutes
a basic factor in controlling climate.
The loss of forest vegetative cover means less heat absorption translating to less moisture being taken up into the atmosphere.
Rainfall is also affected when forest-clearing fires create air pollution and release tiny particles, known as aerosols, into the atmosphere. While aerosols can both heat and cool the air, depending on their size, shape, and color, high concentrations of biomass-burning aerosols directly impact local climate by increasing cloud formation but decreasing rainfall, according to research by NASA. In areas with lots of smoke, "cloud droplets form around the aerosol particles, but may never grow large enough to fall as rain," say researchers with NASA's Goddard Space Flight Center who studied the effect. Thus large forest fires have the effect of further reducing rainfall, leaving burned areas more prone to dryness and future fires.
In the long run, these changes explain why deforested regions may experience a decline in rainfall.
Tropical deforestation can also affect weather in other parts of the world. A 2005 study by NASA found that deforestation in the Amazon region of South America influences rainfall from Mexico to Texas and in the Gulf of Mexico, while forest loss in Central Africa affects precipitation patterns in the upper and lower U.S Midwest. Similarly, deforestation in Southeast Asia was found to impact rainfall in China and the Balkan Peninsula.
Deforestation emissions should be shared between producer and consumer, argues study
(11/19/2009) Under the Kyoto Protocol the nation that produces carbon emission takes responsibility for them, but what about when the country is producing carbon-intensive goods for consumer demand beyond its borders? For example while China is now the world's highest carbon emitter, 50 percent of its growth over the last year was due to producing goods for wealthy countries like the EU and the United States which have, in a sense, outsourced their manufacturing emissions to China. A new study in Environmental Research Letters presents a possible model for making certain that both producer and consumer share responsibility for emissions in an area so far neglected by studies of this kind: deforestation and land-use change.
Oceans' ability to sequester carbon diminishing
(11/18/2009) A new study—the first of its kind—has completed an annual accounting of the oceans' intake of carbon over the past 250 years, and the news is troubling. According to the study, published in Nature, the oceans' ability to sequester carbon is struggling to keep-up with mankind's ever-growing emissions. Since 2000 researchers estimate that while every year the oceans continue to sequester more anthropogenic carbon emission, the overall proportion of carbon taken in by the oceans is declining.
Record year for CO2 emissions, even with economic slowdown
(11/17/2009) 8.7 billion tons of carbon dioxide was emitted into the earth's atmosphere in 2008, a growth of 2 percent despite the economic crisis. This averages out to each person contributing a record high of 1.3 tons of carbon, according to a report in the journal Nature Science. While the global recession slowed the growth of fossil fuel emissions for the first time this decade, it did not lower emissions altogether.
Coastal habitats may sequester 50 times more carbon than tropical forests by area
(11/16/2009) Highly endangered coastal habitats are incredibly effective in sequestering carbon and locking it away in soil, according to a new paper in a report by the IUCN. The paper attests that coastal habitats—such as mangroves, sea grasses, and salt marhses—sequester as much as 50 times the amount of carbon in their soil per hectare as tropical forest. "The key difference between these coastal habitats and forests is that mangroves, seagrasses and the plants in salt marshes are extremely efficient at burying carbon in the sediment below them where it can stay for centuries or even millennia."
Holding the Global North Responsible for Climate Change: What Would Lord Russell Do?
(11/16/2009) If Lord Bertrand Russell were still alive today, he would most likely be appalled by the Global North’s glaring inaction on climate change. One of the twentieth century’s most eminent philosophers, Russell was also an outspoken critic of war and irrationality. In 1966, just as the United States was ramping up the war in Vietnam, Russell helped to establish a novel legal tribunal which condemned war crimes committed in South East Asia.
