Large Scale Forest Fires Gaseous Particulate Emissions and Ecosystem Impacts

Choking smoke interrupted air and ship transportation in and around the islands of Sumatra and Borneo in early October 2006 as detailed in http://earthobservatory. nasa.gov/Newsroom/NewImages/images.php3?img_id= 17423. Fires on the two islands were churning out a blanket of haze that mingled with clouds and reduced visibility to unsafe levels. In addition to their immediate impacts on air quality and human society, fires in tropical lowland forests affect increasingly threatened habitat for rainforest plants and animals, including the endangered orangutans. And because they release significant amounts of carbon dioxide and particle pollution, such as soot, the fires affect the global climate.

The October 2006 fires in Sumatra and Borneo had been burning for several weeks before the images in Figure 4 were taken. During the regional dry season

(roughly August-October), fires are common. Sometimes, fires are the result of slash-and-burn deforestation - clearing of rainforest for palm plantations, for example. At other times, the fires escape during brush clearing or other maintenance activities on already cleared land. Fires in the islands' low-lying forests and peat swamps generate massive amounts of smoke. Because these low-lying forests

Natural color

Shortwave- and near-infrared enhanced

Figure 4 Fires in Sumatra and Borneo in early October 2006. This pair of images from the moderate resolution imaging spectroradiometer (MODIS) on NASA's Aqua satellite from Sunday, 8 October 2006, shows the haze in the area. The top image is a photo-like image, made from MODIS' observations of visible light. Smoke appears grayish white in contrast to the bright white of clouds. Fires detected by MODIS are marked in red. The bottom image is made from a combination of VIS, short-wave IR, and N-IR light. Because smoke is more transparent in the short-wave and N-IR part of the light spectrum than it is in the VIS part, this 'false-color' type of image thins the haze and permits a view at the islands below. Smoke is transparent blue, clouds made of water droplets are white, clouds made of ice crystals are bright blue, vegetation is bright green, and the ocean is dark blue to black. Credit: NASA image created by Jesse Allen, Earth Observatory, using data provided courtesy of the MODIS Rapid Response System team (http:// rapidfire.sci.gsfc.nasa.gov/).

Shortwave- and near-infrared enhanced

Figure 4 Fires in Sumatra and Borneo in early October 2006. This pair of images from the moderate resolution imaging spectroradiometer (MODIS) on NASA's Aqua satellite from Sunday, 8 October 2006, shows the haze in the area. The top image is a photo-like image, made from MODIS' observations of visible light. Smoke appears grayish white in contrast to the bright white of clouds. Fires detected by MODIS are marked in red. The bottom image is made from a combination of VIS, short-wave IR, and N-IR light. Because smoke is more transparent in the short-wave and N-IR part of the light spectrum than it is in the VIS part, this 'false-color' type of image thins the haze and permits a view at the islands below. Smoke is transparent blue, clouds made of water droplets are white, clouds made of ice crystals are bright blue, vegetation is bright green, and the ocean is dark blue to black. Credit: NASA image created by Jesse Allen, Earth Observatory, using data provided courtesy of the MODIS Rapid Response System team (http:// rapidfire.sci.gsfc.nasa.gov/).

and swamp areas are inundated throughout parts of the year, the decay of dead vegetation on the ground proceeds slowly. The thick layers of dead, but undecayed, vegetation - peat - accumulate over many years. Fires burning in dry peat are very smoky and difficult to extinguish. Some can burn underground for years.

Large- and small-scale agriculture are not the only contributors to the fires. The droughts Indonesia experiences during El Nino episodes, such as the particularly severe 1997-98 event, make the forests and peat lands more likely to catch fire. Forests that have been degraded by logging are also more likely to burn. According to a study by Page et al., somewhere between 0.81 and 2.57 million tons of carbon were released by tropical lowland forest and peat land fires in Indonesia in 1997.

The recent (23 October 2007) fires in California, as captured by MODIS on NASA's Terra satellite, can be seen at http://earthobservatory.nasa.gov/Newsroom/ NewImages/images.php3?img_id=17810.

Quite remarkable are the dense smoke plumes stretching over the Pacific for hundreds of kilometers. The growth and spread of the fires were fanned or 'fueled' by the powerful Santa Ana winds that whip from the high-altitude deserts of the Great Basin toward the Pacific Ocean.

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