Incêndios na Amazônia Brasileira: estimativa da emissão de gases do efeito estufa pela queima de diferentes ecossistemas de Roraima na passagem do evento “El Nino” (1997/98)

Tropical forests are global epicentres of biodiversity and important modulators of the rate of climate change. Recent research on deforestation rates and ecological changes within intact forests, both areas of recent research and debate, are reviewed, and the implications for biodiversity (species loss) and climate change (via the global carbon cycle) addressed. Recent impacts have most likely been: (i) a large source of carbon to the atmosphere, and major loss of species, from deforestation and (ii) a large carbon sink within remaining intact forest, accompanied by accelerating forest dynamism and widespread biodiversity changes. Finally, I look to the future, suggesting that the current carbon sink in intact forests is unlikely to continue, and that the tropical forest biome may even become a large net source of carbon, via one or more of four plausible routes: changing photosynthesis and respiration rates, biodiversity changes in intact forest, widespread forest collapse via drought, and widespread forest collapse via fire. Each of these scenarios risks potentially dangerous positive feedbacks with the climate system that could dramatically accelerate and intensify climate change. Given that continued land-use change alone is already thought to be causing the sixth mass extinction event in Earth's history, should such feedbacks occur, the resulting biodiversity and societal consequences would be even more severe.

Concern about the future of Amazonian forests is growing as both the extent and rate of primary forest destruction increase. We combine spatial information on various biophysical, demographic and infrastructural factors in the Brazilian Amazon with satellite data on deforestation to evaluate the relative importance of each factor to deforestation in the region. We assess the sensitivity of results to alternative sampling methodologies, and compare our results to those of previous empirical studies of Amazonian deforestation. Our findings, in concert with those of previous studies, send a clear message to planners: both paved and unpaved roads are key drivers of the deforestation process. Proximity to previous clearings, high population densities, low annual rainfall, and long dry seasons also increase the likelihood that a site will be deforested; however, roads are consistently important and are the factors most amenable to policymaking. We argue that there is ample evidence to justify a fundamental change in current Amazonian development priorities if additional largescale losses of forests and environmental services are to be avoided. Published by Elsevier Ltd.

Luís Antônio Coimbra Borges 3 RESUMO: O presente trabalho consiste em um estudo da legislação Brasileira a respeito do uso do fogo como uma ferramenta para a agricultura. O fogo traz uma série de facilidades e benefícios ao produtor, já que prepara a terra para o cultivo e é barato e acessível. Porém, ao sair do controle, o fogo, gera muitos impactos ao ambiente e a sociedade. Na Amazônia o problema é ainda mais grave, pois o uso do folgo é cultural e pra muitos produtores isolados, a única opção, visto que não é possível ter acesso às novas tecnologias e ferramentas. Com auxílio da pesquisa bibliográfica, este trabalho teve como objetivo conhecer a situação do fogo na Amazônia assim como os impactos causados pelo mesmo. O trabalhou mostrou que o problema do uso do fogo na Amazônia é grave, pois ainda não existem tecnologias acessíveis aos pequenos agricultores isolados da região e o fogo continua sendo utilizado sem as devidas precauções. Grandes incêndios acontecem frequentemente na região e os mesmos têm gerado muitos impactos no meio ambiente e na sociedade.Palavras-chave: Uso do fogo. Queimadas na Amazônia. Impactos ambientais. 1Mestranda em Engenharia Florestal, UFLA. analuisa.cabral@outlook.com.