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Aerial view of erosion in Madagascar. (Photo by R. Butler)
LOCAL AND NATIONAL CONSEQUENCES
LOSS OF LOCAL CLIMATE REGULATION
The local level is where deforestation has the most immediate effect. With forest loss, the local
community loses the system that performed valuable but often underappreciated services like ensuring the regular flow of clean
water and protecting the community from flood and drought. The forest acts as a sort of sponge, soaking up rainfall brought by tropical storms while anchoring soils and releasing water at regular intervals. This regulating feature of tropical rainforests can help moderate destructive flood and drought cycles that can occur when forests are cleared.
When forest cover is lost, runoff rapidly flows into streams, elevating river levels and subjecting downstream villages, cities, and agricultural fields to flooding, especially during the rainy season. During the dry season, such areas downstream of deforestation can be prone to months-long droughts which interrupt river navigation, wreak havoc on crops, and disrupt industrial operations.
Situated on steep slopes, montane and watershed forests are especially
important in ensuring water flow and inhibiting erosion, yet during the 1980s, montane formations suffered the
highest deforestation rate of tropical forests.
Aerial view of erosion in western Madagascar
Does deforestation cause flooding?
Not directly, according to a 2005 study by the UN's Food and Agriculture Organization (FAO) and the Center for International Forestry Research (CIFOR). The groups found that the frequency and extent of major floods has not changed over the last century despite significant reductions in forest cover. Instead, FAO and CIFOR say that deforestation does have a role in small floods and topsoil erosion by eliminating the buffering and soil-anchoring effects of forests. Further, the report accuses Asian governments of using deforestation as an excuse to deflect criticism over their poor handling of human settlement in areas unsuitable for habitation. UPDATE: A 2007 study found that forests do impact the occurrence and severity of destructive floods.
Additionally, the forest adds to local humidity through transpiration (the process by which plants release water
through their leaves), and thus adds to local rainfall. For example, 50-80 percent of the moisture in the central and
western Amazon remains in the ecosystem water cycle. In the water cycle, moisture is transpired and evaporated
into the atmosphere, forming rain clouds before being precipitated as rain back onto the forest. When the forests
are cut down, less moisture is evapotranspired into the atmosphere resulting in the formation of fewer rain clouds.
Subsequently there is a decline in rainfall, subjecting the area to drought. If rains stop falling, within a few years the
area can become arid with the strong tropical sun baking down on the scrub-land. Today Madagascar is largely a
red, treeless desert from generations of forest clearing with fire. River flows decline and smaller amounts of quality
water reach cities and agricultural lands. The declining rainfall in interior West African countries has in part
been attributed to excessive clearing of the coastal rainforests. Similarly, new research in Australia suggests
that if it were not for human influences—specifically widespread agricultural fires—the dry outback might be
a wetter, more hospitable place than it is today. The effect of vegetation change from forests that favor rainfall
to grassland and bush can impact precipitation patterns. Colombia, once second in the world with freshwater reserves, has fallen
to 24th due to its extensive deforestation over the past 30 years. Excessive deforestation around the Malaysian
capital of Kuala Lumpur, combined with the dry conditions created by el Niño, triggered strict water rationing
in 1998, and for the first time the city had to import water.
There is serious concern that widespread deforestation could lead to a significant decline in rainfall and
trigger a positive-feedback process of increasing dessication for neighboring forest cover; reducing its moisture
stocks and its vegetation would then further the dessication effect for the region. Eventually the effect could extend
outside the region, affecting important agricultural zones and other watersheds. At the 1998 global climate treaty
conference in Buenos Aires, Britain, citing a disturbing study at the Institute of Ecology in Edinburgh, suggested
the Amazon rainforest could be lost in 50 years due to shifts in rainfall patterns induced by global warming and
land conversion.
The newly dessicated forest becomes prone to devastating fires. Such fires materialized in 1997 and 1998 in conjunction
with the dry conditions created by el Niño. Millions of acres burned as fires swept through Indonesia, Brazil,
Colombia, Central America, Florida, and other places. The Woods Hole Research Center warned that more than 400,000 square kilometers of Brazilian Amazonia were highly vulnerable to fire in 1998.
Water wars?
Such losses of freshwater resources are considered one of the most immediate threats to national security in many countries. Freshwater—required for human consumption, agriculture, and industrial operations—or the lack thereof can have a tremendous effect on the social, economic, and political climate of a country. Realizing the importance of water, politicians of the future may try to secure their existing freshwater supplies or wage war to acquire other sources of water. Demand for water increases as the standard of living improves, so politicians of the future will look to guarantee freshwater supplies. Developing countries, where political and social conditions are often tense, will likely experience the most pressure from shrinking water supplies. In the future, wars may be fought over water, not oil. Already Egypt has made it known to its upstream neighbors—Sudan and Ethiopia—that it is willing to go to war over the Nile's water
Review questions:
How do rainforests help moderate flood and drought cycles?
Starving hyenas kill and eat 12-foot-long python during drought
(01/05/2010) Members with the conservation group Lion Guardians stumbled on a rare site in the Amboseli area of Kenya recently: six hyenas and a number of jackals were attacking and eating a 12-foot-long python. On their blog at WildlifeDirect, Lion Guardians describe the attack: "[the hyenas and jackals] tore into its body from the back, and were taking their share while the upper part of the python was still alive! The Lion Guardian team was shocked and surprised at the same time, having never seen anything like it before."
Pope Benedict: environmental crisis requires review of world's economic model
(12/15/2009) Pope Benedict XVI has released a message linking world peace with preserving the environment for the World Day of Peace, which will be held on January 1st 2010. In it Benedict calls for a "long-term review" of the world's current economic model, including "[moving] beyond a purely consumerist mentality" and encouraging a more "sober lifestyle".
Photos: ten beloved species threatened by global warming
(12/14/2009) The International Union for the Conservation of Nature (IUCN) has released a list of ten species that are likely to be among the hardest hit by climate change, including beloved species such as the leatherback sea turtle, the koala, the emperor penguin, the clownfish, and the beluga whale. The timing of the list coincides with the negotiations by world leaders at the UN Climate Change Conference to come up with an international agreement to combat climate change.
Current decade is the warmest on record
(12/08/2009) As 192 countries meet in Copenhagen to wrangle out a complex and at times sticky agreement to combat climate change, the World Meteorological Organization (WMO) has released new evidence that the world is undergoing warming. According to the WMO the current decade is likely the warmest on record.
Profile of the carbon footprint of the global poor: the challenge of alleviating poverty and fighting global warming
(12/07/2009) Two of the world's most serious issues—poverty and climate change—are interconnected. With a rise in one's income there usually comes a rise in one's carbon footprint, thereby threatening the environment. Wealthy nations have the highest per capita carbon footprints, while developing nations like India and China—which are experiencing unprecedented economic growth—are becoming massive contributors of greenhouse gases. However, it is those who have the smallest carbon footprint—the world's poor—who currently suffer most from climate change. Food crises, water shortages, extreme weather, and rising sea levels have all hit the poor the hardest.