Tropical Deforestation

by Rebecca Lindsey

Stretching out from the equator on all Earth’s land surfaces is a wide belt of forests of amazing diversity and productivity. Tropical forests include dense rainforests, where rainfall is abundant year-round; seasonally moist forests, where rainfall is abundant, but seasonal; and drier, more open woodlands. Tropical forests of all varieties are disappearing rapidly as humans clear the natural landscape to make room for farms and pastures, to harvest timber for construction and fuel, and to build roads and urban areas. Although deforestation meets some human needs, it also has profound, sometimes devastating, consequences, including social conflict, extinction of plants and animals, and climate change—challenges that aren’t just local, but global. NASA supports and conducts research on tropical forests from space-based and ground-based perspectives, helping provide the information that national and international leaders need to develop strategies for sustaining human populations and preserving tropical forest biodiversity.

 Impacts of Deforestation: Biodiversity Impacts

Although tropical forests cover only about 7 percent of the Earth’s dry land, they probably harbor about half of all species on Earth. Many species are so specialized to microhabitats within the forest that they can only be found in small areas. Their specialization makes them vulnerable to extinction. In addition to the species lost when an area is totally deforested, the plants and animals in the fragments of forest that remain also become increasingly vulnerable, sometimes even committed, to extinction. The edges of the fragments dry out and are buffeted by hot winds; mature rainforest trees often die standing at the margins. Cascading changes in the types of trees, plants, and insects that can survive in the fragments rapidly reduces biodiversity in the forest that remains. People may disagree about whether the extinction of other species through human action is an ethical issue, but there is little doubt about the practical problems that extinction poses.

 
First, global markets consume rainforest products that depend on sustainable harvesting: latex, cork, fruit, nuts, timber, fibers, spices, natural oils and resins, and medicines. In addition, the genetic diversity of tropical forests is basically the deepest end of the planetary gene pool. Hidden in the genes of plants, animals, fungi, and bacteria that have not even been discovered yet may be cures for cancer and other diseases or the key to improving the yield and nutritional quality of foods—which the U.N. Food and Agriculture Organization says will be crucial for feeding the nearly ten billion people the Earth will likely need to support in coming decades. Finally, genetic diversity in the planetary gene pool is crucial for the resilience of all life on Earth to rare but catastrophic environmental events, such as meteor impacts or massive, sustained volcanism.

Soil Impacts

With all the lushness and productivity that exist in tropical forests, it can be surprising to learn that tropical soils are actually very thin and poor in nutrients. The underlying “parent” rock weathers rapidly in the tropics’ high temperatures and heavy rains, and over time, most of the minerals have washed from the soil. Nearly all the nutrient content of a tropical forest is in the living plants and the decomposing litter on the forest floor.

 
When an area is completely deforested for farming, the farmer typically burns the trees and vegetation to create a fertilizing layer of ash. After this slash-and-burn deforestation, the nutrient reservoir is lost, flooding and erosion rates are high, and soils often become unable to support crops in just a few years. If the area is then turned into cattle pasture, the ground may become compacted as well, slowing down or preventing forest recovery.

Social Impacts

Tropical forests are home to millions of native (indigenous) people who make their livings through subsistence agriculture, hunting and gathering, or through low-impact harvesting of forest products like rubber or nuts. Deforestation in indigenous territories by loggers, colonizers, and refugees has sometimes triggered violent conflict. Forest preservation can be socially divisive, as well. National and international governments and aid agencies struggle with questions about what level of human presence, if any, is compatible with conservation goals in tropical forests, how to balance the needs of indigenous peoples with expanding rural populations and national economic development, and whether establishing large, pristine, uninhabited protected areas—even if that means removing current residents—should be the highest priority of conservation efforts in tropical forests.

Articel Source:  www.earthobservatory.nasa.gov/Features/Deforestation/

Drought and deforestation in southeast Asia to contribute to climate change

by. Rhett A. Butler

Fires linked to drought and deforestation in Borneo, Sumatra, and New Guinea trigger the releaseof 3.3 billion tons of CO2 between 2000-2006 

Researchers have linked drought and deforestation in southeast Asia to climate change. 

Analyzing six years of climate and fire data from satellites, Guido van der Werf and colleagues report that burning of rainforests and peatlands in Indonesia, Malaysia, and Papua New Guinea released an average of 128 million tons of carbon (470 million tons of carbon dioxide - CO2) per year between 2000 and 2006. Fire emissions showed highly variability during the period, but were greatest in dry years, such as those that occur during El Niño events. Borneo was the largest source of fire emissions during the period, averaging 74 million tons per year, followed by Sumatra, which showed a doubling in emissions between 2000 and 2006. Both islands are experiencing rapid forest destruction due to logging and conversion to industrial oil palm plantations. Forests are usually logged and then burned to establish plantations. Previously analyses have shown a high correlation between the location of fire hot spots and plantations in both Malaysia and Indonesia. 
 
The researchers say their results highlight the importance of including deforestation in future climate agreements. 

"Deforestation and carbon emissions are substantial and important contributors to the buildup of greenhouse gases in the atmosphere," James Randerson, climate scientist at UCI and co-author of the study, said. "We should not neglect this flux in developing comprehensive approaches for stabilizing climate." 

Reducing emissions from deforestation and forest degradation (REDD) is indeed under discussion at current climate talks in Poznan, Poland, although the mechanism is being held up due to technical debates and poor coordination among some parties. Globally deforestation accounts for roughly 20 percent of emissions — greater than all the world's cars, trucks, planes, and ships combined. In some years, such 1997-1998 which was marked by a particularly strong Niñ;o event; deforestation and emissions from vegetation burning can account for more than one-third of total anthropogenic emissions. 

Forest loss exacerbates drying by reducing evapotranspiration by trees. Smoke can also inhibit rainfall while changes in surface reflectivity or albedo can discourage the formation of rain clouds. 

Fire as a climate variable 

Given the influence of human land management practices on climate, the authors conclude by suggesting that future climate models incorporate anthropogenic use of fire as a carbon–climate feedback mechanism. 

"To date, climate–carbon cycle feedbacks have been mostly modeled as an interaction of canopy-level processes such as reduced net primary productivity and increased soil respiration in response to temperature increases," they write. "Our results provide evidence that the response of human agents (land users) to drought may comprise an equally important class of carbon–climate feedback mechanisms in the tropics. Without proper mitigation strategies, emissions from this region have the potential to increase substantially as climate projections suggest future drying and warming. 

CITATION: G. R. van der Werfa at al (2008). Climate regulation of fire emissions and deforestation in equatorial Asia. PNAS Early Edition December 8, 2008

Article Source:  www.mongabay.com

80% of agricultural expansion since 1980 came at expense of forests

More than half of cropland expansion between 1980 and 2000 occurred at the expense of natural forests, while another 30 percent of occurred in disturbed forests, reported a Stanford University researcher presenting Saturday at the annual meeting of the American Association for the Advancement of Science (AAAS) in Chicago. 

Holly Gibbs, formerly of the University of Wisconsin-Madison, reached her conclusion after analyzing more than 600 satellite images from the United Nations Food and Agricultural Organization (FAO) and other organizations. 

"What we found was that indeed forests were the primary source for new croplands as they expanded across the tropics during the 1980s and 1990s," Gibbs explained. "Cropland expansion, whether it's for fuel, feed or food, has undoubtedly led to more deforestation, and evidence is mounting that this trend will continue." 

"This is a major concern for the global environment," she continued. "As we look toward biofuels to help reduce climate change we must consider the rainforests and savannas that may lie in the pathway of expanding biofuel cropland." 
 
Oil palm plantations and logged over forest in Malaysian Borneo. While much of the forest land converted for oil palm plantations in Malaysia has been logged or otherwise been zoned for logging, expansion at the expense of natural and protected forest does occur in the country. Reserve borders are sometimes redrawn to facilitate logging and conversion to plantations. 

Conversion of natural ecosystems for production of biofuel feedstocks like corn and sugar cane for ethanol, and soy and palm oil for biodiesel, can result in substantial greenhouse gas emissions since these croplands sequester less carbon than the forests and wetlands they replace. For example the production of a single ton of palm oil on land converted from peat forest in Indonesia can result in 25 to 70 tons in carbon dioxide emissions from clearing of vegetation, draining of swampy soils, and burning. 

Gibbs says the FAO is currently in the process of gathering data that will reveal the impact of the recent biofuels boom on forests and other ecosystems. She hopes the data can be used to influence policy makers to steer future agricultural expansion towards abandoned and degraded agricultural lands rather than forests. 

"I think that biofuels may have a critical place in our future energy plan, but the way that we're currently going about producing biofuels could have a lot of unintended consequences," she said. "The new administration should carefully consider the full consequences of any energy plan to make sure we protect the carbon stored in rainforests as well as reduce our fossil fuel emissions."

Article Source:  www.mongabay.com