[Fig.1 Scores of active fires were burning in eastern India and the mountainous provinces of northwest Burma (Myanmar) on March 9, 2009, when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite passed overhead and captured this photo-like image. Locations where the sensor detected active fires are outlined in red. Agricultural and other land-maintenance fires are common in the area this time of year (dry season), so many of these fires were probably intentionally started by people. However, as in all parts of the world, intentional fires occasionally get out of control. Some of the larger or smokier fires in this scene could be accidental forest fires.Image credit: Jeff Schmaltz, NASA's MODIS Rapid Response TeamText credit: Rebecca Lindsey, NASA's Earth Observatory.]
Forest Fires in Nepal
[Fig. 2. On March 12, 2009, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite caught a glimpse of a relatively rare event: large–scale forest fires in the Himalaya Mountains of Nepal. Places where the sensor detected active fires are outlined in red. The numerous small fires in southern Nepal may not be wildfires, but rather agricultural or other land-management fires.The image is centered on Nepal, and it shows the towering Himalaya Mountains arcing through the small country. Many national parks and conservation areas are located along the northern border of the country, and the fires appear to be burning in or very near some of them. Five people were killed by the forest fire southwest of Annapurna in early March; according to a news report they were overtaken while in the forest gathering firewood. According to that report, Nepal commonly experiences some small forest fires each spring, which is the end of the dry season there. However, conditions during the fall and winter of 2008 and 2009 were unusually dry, and fires set by poachers to flush game may have gotten out of control.Image credit: Jeff Schmaltz, NASA's MODIS Rapid Response TeamText credit: Rebecca Lindsey, NASA's Earth Observatory ]
Fires in West Africa
The forest is also vital as a watershed. Because of the thick humus layer, loose soil, and soil-retaining powers of the trees' long roots, forests are vitally important for preserving adequate water supplies. Almost all water ultimately feeds from forest rivers and lakes and from forest-derived water tables. In addition, the forest provides shelter for wildlife, recreation and aesthetic renewal for people, and irreplaceable supplies of oxygen and soil nutrients. Deforestation, particularly in the tropical rain forests, has become a major environmental concern, as it can destabilize the earth's temperature, humidity, and carbon dioxide levels.
Besides being the source for food, plants help us in a number of other ways. Animals, including humans, inhale oxygen and exhale carbon dioxide; plants take up carbon dioxide and in return they release oxygen – this exchange is very important. Forests in particular act as a huge carbon dioxide sink. If there were not enough trees to absorb carbon dioxide, its accumulation would make the environment poisonous. Over the last 150 years, the amount of carbon dioxide has increased.
While all living plant matter absorbs CO2 as part of photosynthesis, trees process significantly more than smaller plants due to their large size and extensive root structures. In essence, trees, as kings of the plant world, have much more “woody biomass” to store CO2 than smaller plants, and as a result are considered nature’s most efficient “carbon sinks.”
According to the U.S. Department of Energy (DOE), tree species that grow quickly and live long are ideal carbon sinks.
Forests are carbon stores, and they are carbon dioxide sinks when they are increasing in density or area. In Canada's boreal forests as much as 80% of the total carbon is stored in the soils as dead organic matter. A 40-year study of African, Asian, and South American tropical forests by the University of Leeds, shows tropical forests absorb about 18% of all carbon dioxide added by fossil fuels, thus buffering some effects of global warming. Tropical reforestation can mitigate global warming until all available land has been reforested with mature forests. About 70-80 billion tonnes of carbon dioxide are fixed annually by terrestrial and aquatic photoautotrophs.
Life expectancy of forests varies throughout the world, influenced by tree species, site conditions and natural disturbance patterns. In some forests carbon may be stored for centuries, while in other forests carbon is released with frequent stand replacing fires.
From the last hundred years forests are being reduced drastically due to forest fire, the most common hazard in forests. Though the forests fires are as old as the forests
themselves, but in recent years the incidence of forest fire, either man made or natural, has increased many fold.
During the 1997-98 El Nino 20M hectares burnt. This one event released 2.6 billion tons of carbon - the highest annual increase since measurements began. They were so massive that the output of CO2 from combustion reached 40% of the world total. This happened again in 2006.
Indonesian fires have shown us that catastrophic events in small areas can release vast amounts that have been locked away for millennia.