Land-use fires and wildfires are still burning in the region of Paraguay, Bolivia, and Brazil. The vegetation types affected by fires are dry and semi-humid Chaco (Chaco seco and semi-húmedo), Cerrado and some deciduous and semi-deciduous forests (on the Brazilian side). The vegetation of the Chaco region is a mixture of savannas, thorn shrublands and hardwood forests alternating in belts and patches. Evidence suggests that fire has been a natural component of the Chaco ecosystem for thousands of years. Indians used fire for warfare and hunting; in fact, “Chaco” means “a site for hunting” in the Quichua language. During the dry season large fires regularly sweep across the savannas and shrublands and on some occasions hit the hardwood forest that burn with high intensity. Tolerance of species to fire is mixed. The fire cycle is around 3-5 years in savannas. Some of the Chaco areas are “Palmares”, open palm stands with periodically waterlogged grass understorey which are fire adapted.
The Brazilian Institute for Environment and Natural Resources (IBAMA) conducted an extensive study of burning activities in the Amazon region which is generally refereed to as “Arc of Deforestation” (arco do desflorestamento) in which the forest conversion by fire and wildfire activities are predominantly occurring.
Fig.3. Arc of Deforestation in Brazil (Source: IBAMA 1998)
IBAMA differentiates between two kinds of vegetation fires, agricultural burnings (queimadas), where fire is traditionally used as a tool for preparing pasture or crop land. The other type of vegetation fire is defined as “uncontrolled fire in any kind of vegetation, caused either by man or natural causes” (“wildfire” or “forest fire”).
Most of the fires in Brazil must be seen in the context of intensive land development. Fire is used as a tool in forest conversion. This is done by small farmers as well as large agro-industrial companies. The careless use of fire often allow the “prescribed” burnings to escape and become forest fires in the adjacent forests. These wildfires are of global importance because they threaten global biodiversity as well as the livelihood and cultural identity of the indigenous people in Amazonia.
Almost all fires in the Amazon Region are human-caused, natural fires play a minor role in the tropical rain forest of Brazil and neighbouring countries. In the seasonally dry forests and bush formations (cerrado) lightning fires are observed occasionally.
Under normal weather conditions the primary forest in the humid tropics does not catch fire. The hydrological cycle in the closed forests produces a very humid microclimate where unfavourable conditions for forest fire exist. But in forests where selective logging already took place the former closed canopy is disturbed. This allows more light to penetrate through the canopy and thereby changing the energy balance within the forest – the forest becomes more susceptible to drought. With trees shedding their leaves in the extreme drought stress caused by the El Nino event in 1998 the fuel for forest fires increases dramatically and the risk of high intensity wildfires increases.
The following town regions in the State of Para and Apiacas, Mato Grosso and Rondonia were identified by IBAMA as high risk areas for destructive forest fires. This classification is based on the fact that in this region logging, mining and illegal prospecting and free range cattle rearing are concentrated in Brazil:
Tab.1. Town regions with high risk of forest fires
State of Para and Apiacas
State of Mato Grosso
State of Rondonia
Paragominas Conceicao do Araguaia Eldorado dos Carajas Maraba Parauapebas Redencao
Alta Floresta Nova Canaa do Norte Colider Sinop Peixoto Azevedo Sao Felix do Xingu Porto Alegre do Norte Luciara Santa Terezinha
Ji-Parana Ariquemes Alto Paraiso Nova Mamore
The Woods Hole Research Center (WHRC) and IPAM Instituto de Pesquisa Ambiental da Amazonia have prepared an Information Bulletin for the Buenos Aires Climate Conference. The bulletin describes the early warning of the upcoming fire seaon in Brazil early 1998 and the extent of damage. The bulletin provides also links to the WHRC and IPAM websites.
A detailed study on the spatio-temporal dynamics of the Boa Vista- Roraima fire events by the Space Applications Institute of the Joint Research Centre European Commission (Ispra,Varese) for the CLAIRE/LBA study can be seen at: http://www.mtv.sai.jrc.it/parbo/Roraima_Web.html.
The Brazilian Environmental Monitoring Centre (NMA) EcoForca is an Brazilian NGO which gives extensive information about issues like deforestation, forest fires etc. in Brazil. The NMA website provides background information to the current situation in Brazil.
References: IBAMA 1998.Programa de Prevencao e Controle as Queimadas e aos Incendios Florestais no Arco de Desflorestamento “PROARCO”. IBAMA, Brasilia, 49 p. (The full text of the documentation is available in Portuguese under http://www.ibama.gov.br/).
Flames in the Rain Forest – A comprehensive and alarming study on fire in Brazil’s Amazon forest. Source: D.C.Nepstad, A.G.Moreira, and A.A.Alencar. 1999. Flames in the rain forest: Origins, impacts and alternatives to Amazonian fire. Pilot Program to Conserve the Brazlian Rain Forest. Ministry of Environment, Secretariat for the Coordination of Amazon.
Forests on Fire – A review on fires in the world’s rain forests, particularly in Brazil and Indonesia. Published in Science, Vol. 284, pp. 1782-83, 11 June 1999 (will be added later to the GFMC website).
Cryptic Deforestation – A recent article by a joint Brazilian-US group of scientists on the impact of forest fires on forest impoverishment in Brazil’s Amazon region, published inNature.