Suchergebnisse

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) ; Empresa Brasileira de Pesquisa Agropecuaria - Embrapa ; UK Government Darwin Initiative ; Nature Conservancy ; UK Natural Environment Research Council (NERC) ; H2020-MSCA-RISE-2015 ; CNPq: 574008/2008-0 ; Empresa Brasileira de Pesquisa Agropecuaria - Embrapa: SEG: 02.08.06.005.00 ; UK Government Darwin Initiative: 17-023 ; UK Natural Environment Research Council (NERC): NE/ F01614X/1 ; UK Natural Environment Research Council (NERC): NE/G000816/1 ; UK Natural Environment Research Council (NERC): NE/K016431/1 ; UK Natural Environment Research Council (NERC): NE/P004512/1 ; H2020-MSCA-RISE-2015: 691053-ODYSSEA ; CNPq: PELD-RAS 441659/2016-0 ; CNPq: 458022/2013-6 ; CNPq: 305054/ 2016-3 ; Wildfires produce substantial CO2 emissions in the humid tropics during El Nino-mediated extreme droughts, and these emissions are expected to increase in coming decades. Immediate carbon emissions from uncontrolled wildfires in human-modified tropical forests can be considerable owing to high necromass fuel loads. Yet, data on necromass combustion duringwildfires are severely lacking. Here, we evaluated necromass carbon stocks before and after the 2015-2016 El Nino in Amazonian forests distributed along a gradient of prior human disturbance. We then used Landsat-derived burn scars to extrapolate regional immediate wildfire CO2 emissions during the 20152016 El Nino. Before the El Nino, necromass stocks varied significantly with respect to prior disturbance and were largest in undisturbed primary forests (30.2 +/- 2.1 Mg ha(-1), mean +/- s. e.) and smallest in secondary forests (15.6 +/- 3.0 Mg ha(-1)). However, neither prior disturbance nor our proxy of fire intensity (median char height) explained necromass losses due towildfires. In our 6.5 million hectare (6.5 Mha) study region, almost 1 Mha of primary (disturbed and undisturbed) and 20 000 ha of secondary forest burned during the 2015-2016 ElNino. Covering less than 0.2% of Brazilian Amazonia, thesewildfires resulted in expected immediate CO2 emissions of approximately 30 Tg, three to four times greater than comparable estimates fromglobal fire emissions databases. Uncontrolled understoreywildfires in humid tropical forests during extreme droughts are a large and poorly quantified source of CO2 emissions. This article is part of a discussion meeting issue 'The impact of the 2015/2016 El Nino on the terrestrial tropical carbon cycle: patterns, mechanisms and implications'.

Concerted political attention has focused on reducing deforestation1,2,3, and this remains the cornerstone of most biodiversity conservation strategies4,5,6. However, maintaining forest cover may not reduce anthropogenic forest disturbances, which are rarely considered in conservation programmes6. These disturbances occur both within forests, including selective logging and wildfires7,8, and at the landscape level, through edge, area and isolation effects9. Until now, the combined effect of anthropogenic disturbance on the conservation value of remnant primary forests has remained unknown, making it impossible to assess the relative importance of forest disturbance and forest loss. Here we address these knowledge gaps using a large data set of plants, birds and dung beetles (1,538, 460 and 156 species, respectively) sampled in 36 catchments in the Brazilian state of Pará. Catchments retaining more than 69–80% forest cover lost more conservation value from disturbance than from forest loss. For example, a 20% loss of primary forest, the maximum level of deforestation allowed on Amazonian properties under Brazil's Forest Code5, resulted in a 39–54% loss of conservation value: 96–171% more than expected without considering disturbance effects. We extrapolated the disturbance-mediated loss of conservation value throughout Pará, which covers 25% of the Brazilian Amazon. Although disturbed forests retained considerable conservation value compared with deforested areas, the toll of disturbance outside Pará's strictly protected areas is equivalent to the loss of 92,000–139,000 km2 of primary forest. Even this lowest estimate is greater than the area deforested across the entire Brazilian Amazon between 2006 and 2015 (ref. 10). Species distribution models showed that both landscape and within-forest disturbances contributed to biodiversity loss, with the greatest negative effects on species of high conservation and functional value. These results demonstrate an urgent need for policy interventions that go beyond the ...