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Chapter Two: The State of the Environment - Global issues

Forest fires and biomass burning

During 1996-98, fire swept through forests in Australia, Brazil, Canada, China's northeastern Inner Mongolian region, France, Greece, Indonesia, Italy, Mexico and several other countries in Latin America, the Russian Federation, Turkey and the United States. Satellite photos showed that about 3.3 million hectares of Brazilian forest were devastated as a result of the fires. More than 3 million hectares of forest in Mongolia were burnt in 1996. The fires in Southeast Asia in 1997 were the worst in 15 years, with at least 4.5 million hectares burnt, and smoke and haze affecting some 70 million people (Liew and others 1998). The fires in Indonesia threatened at least 19 protected areas, many of which are rich in biodiversity (WWF 1998).

The forests of Southeast Asia and of the Brazilian Amazon were especially vulnerable to fire in 1997 and 1998 because of a severe drought probably related to the strong El Niño of the same period and/or changing global weather patterns. After the severe El Niño of 1982, the largest fires then on record raged across Kalimantan. The 1997 and 1998 fires were far more extensive and coincided with an even more severe El Niño.

In many countries, vegetation, forests, savannahs and agricultural lands are burnt to clear land and change its use. Forest clearing accelerates as populations expand and pressures to exploit natural resources increase. Much of the expansion into forested areas uses the cheapest form of cover removal: fire. Thus increased pressure for development has led to much of the recent fire damage in tropical rain forests as loggers, cattle farmers and peasants take advantage of the dry season to clear land for farming.

In Indonesia and South America, much of the blame for starting fires fell on small farmers. But only 12 per cent of the forest cleared in the Amazon is actually used for arable farming. The remaining 88 per cent is used for pasture. New areas are usually made accessible for ranching and agriculture as a result of the construction of logging roads to extract mahogany (WWF 1997).

The health impacts of forest fires can be serious and widespread. Estimates for the fall-out from fires in Southeast Asia suggest that 20 million people were in danger of respiratory problems. The estimated health cost to the people of Southeast Asia was US$1 400 million, mostly related to short-term health problems (EEPSEA/WWF 1998). In 1997, smoke and air pollution from fires in Guatemala, Honduras and Mexico drifted across much of the southeastern United States, prompting Texas officials to issue a health warning to residents.

Another major consequence of forest fires is their potential impact on global atmospheric problems, including climate change. Only in the past decade have researchers realized the important contributions of biomass burning to the global budgets of carbon dioxide, methane, nitric oxide, tropospheric ozone, methyl chloride and elemental carbon particulates.

 Biomass burning
 

source of burning biomass burned (million tonnes dry matter/year) carbon released (million tonnes carbon/year)

Savannahs 3 690 1 660
Agricultural waste 2 020 910
Tropical forests 1 260 570
Fuelwood 1 430 640
Temperate and boreal forests 280 130
Charcoal 20 30

World total 8 700 3 940

For comparison:    
Global carbon emissions from fossil fuel burning, cement manufacture and gas flaring   6 518

Source: Andreae 1991, CDIAC 1999

 

The extent of biomass burning has increased significantly over the past 100 years. It is now recognized as a significant global source of atmospheric emissions, contributing more than half of all the carbon released into the atmosphere (see table left). The burning of tropical savannahs is estimated to destroy three times as much dry matter per year as the burning of tropical forests (Andreae 1991).

Forest fires are dealt with in more detail in the regional sections on Asia and the Pacific and on Latin America that follow.


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