Spatial patterns and fire response of recent Amazonian droughts
TL;DR: In this paper, the authors analyzed the spatial extent of these droughts and fire response to the 2005 Amazonian drought with TRMM and NOAA-12 data, respectively, and found that the area of leakage forest fires was more than five times greater than the area directly deforested.
Abstract: [1] There has been an increasing awareness of the possibility of climate change causing increased drought frequency in Amazonia, with ensuing impacts on ecosystems and human populations. This debate has been brought into focus by the 1997/1998 and 2005 Amazonian droughts. We analysed the spatial extent of these droughts and fire response to the 2005 drought with TRMM and NOAA-12 data, respectively. Both droughts had distinct fingerprints. The 2005 drought was characterized by its intensification throughout the dry season in south-western Amazonia. During 2005 the annual cumulative number of hot pixels in Amazonia increased 33% in relation to the 1999–2005 mean. In the Brazilian state of Acre, at the epicentre of the 2005 drought, the area of leakage forest fires was more than five times greater than the area directly deforested. Fire leakage into flammable forests may be the major agent of biome transformation in the event of increasing drought frequency.
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Paul Sabatier University1, National Autonomous University of Mexico2, Carnegie Institution for Science3, University of São Paulo4, National University of Colombia5, Norwegian University of Life Sciences6, Amazon.com7, University of Leeds8, United Nations9, Smithsonian Tropical Research Institute10, University of Edinburgh11, Costa Rica Institute of Technology12
TL;DR: This work analyzed a global database of directly harvested trees at 58 sites, spanning a wide range of climatic conditions and vegetation types, and found a pantropical model incorporating wood density, trunk diameter, and the variable E outperformed previously published models without height.
Abstract: Terrestrial carbon stock mapping is important for the successful implementation of climate change mitigation policies. Its accuracy depends on the availability of reliable allometric models to infer oven-dry aboveground biomass of trees from census data. The degree of uncertainty associated with previously published pantropical aboveground biomass allometries is large. We analyzed a global database of directly harvested trees at 58 sites, spanning a wide range of climatic conditions and vegetation types (4004 trees ≥ 5 cm trunk diameter). When trunk diameter, total tree height, and wood specific gravity were included in the aboveground biomass model as covariates, a single model was found to hold across tropical vegetation types, with no detectable effect of region or environmental factors. The mean percent bias and variance of this model was only slightly higher than that of locally fitted models. Wood specific gravity was an important predictor of aboveground biomass, especially when including a much broader range of vegetation types than previous studies. The generic tree diameter-height relationship depended linearly on a bioclimatic stress variable E, which compounds indices of temperature variability, precipitation variability, and drought intensity. For cases in which total tree height is unavailable for aboveground biomass estimation, a pantropical model incorporating wood density, trunk diameter, and the variable E outperformed previously published models without height. However, to minimize bias, the development of locally derived diameter-height relationships is advised whenever possible. Both new allometric models should contribute to improve the accuracy of biomass assessment protocols in tropical vegetation types, and to advancing our understanding of architectural and evolutionary constraints on woody plant development.
1,750 citations
TL;DR: The forest biome of Amazonia is one of Earth's greatest biological treasures and a major component of the Earth system, and this century, it faces the dual threats of deforestation and stress from climate change.
Abstract: The forest biome of Amazonia is one of Earth's greatest biological treasures and a major component of the Earth system. This century, it faces the dual threats of deforestation and stress from climate change. Here, we summarize some of the latest findings and thinking on these threats, explore the consequences for the forest ecosystem and its human residents, and outline options for the future of Amazonia. We also discuss the implications of new proposals to finance preservation of Amazonian forests.
1,552 citations
TL;DR: Records from multiple long-term monitoring plots across Amazonia are used to assess forest responses to the intense 2005 drought, a possible analog of future events that may accelerate climate change through carbon losses and changed surface energy balances.
Abstract: Amazon forests are a key but poorly understood component of the global carbon cycle. If, as anticipated, they dry this century, they might accelerate climate change through carbon losses and changed surface energy balances. We used records from multiple long-term monitoring plots across Amazonia to assess forest responses to the intense 2005 drought, a possible analog of future events. Affected forest lost biomass, reversing a large long-term carbon sink, with the greatest impacts observed where the dry season was unusually intense. Relative to pre-2005 conditions, forest subjected to a 100-millimeter increase in water deficit lost 5.3 megagrams of aboveground biomass of carbon per hectare. The drought had a total biomass carbon impact of 1.2 to 1.6 petagrams (1.2 × 1015 to 1.6 × 1015 grams). Amazon forests therefore appear vulnerable to increasing moisture stress, with the potential for large carbon losses to exert feedback on climate change.
1,545 citations
Max Planck Society1, University of Innsbruck2, Centre national de la recherche scientifique3, ETH Zurich4, Stockholm University5, Oeschger Centre for Climate Change Research6, Tuscia University7, Potsdam Institute for Climate Impact Research8, University of Aberdeen9, International Institute for Applied Systems Analysis10, University of Antwerp11, University of Potsdam12
TL;DR: The mechanisms and impacts of climate extremes on the terrestrial carbon cycle are explored, and a pathway to improve the understanding of present and future impacts ofClimate extremes onThe terrestrial carbon budget is proposed.
Abstract: The terrestrial biosphere is a key component of the global carbon cycle and its carbon balance is strongly influenced by climate. Continuing environmental changes are thought to increase global terrestrial carbon uptake. But evidence is mounting that climate extremes such as droughts or storms can lead to a decrease in regional ecosystem carbon stocks and therefore have the potential to negate an expected increase in terrestrial carbon uptake. Here we explore the mechanisms and impacts of climate extremes on the terrestrial carbon cycle, and propose a pathway to improve our understanding of present and future impacts of climate extremes on the terrestrial carbon budget.
1,290 citations
TL;DR: A review of the current understanding of what the future may bring with respect to wildland fire and future options for research and management is presented in this paper. But, as stated in the review, "wildland fire is a global phenomenon, and a result of interactions between climate, fuels, and people".
Abstract: Wildland fire is a global phenomenon, and a result of interactions between climate–weather, fuels and people. Our climate is changing rapidly primarily through the release of greenhouse gases that may have profound and possibly unexpected impacts on global fire activity. The present paper reviews the current understanding of what the future may bring with respect to wildland fire and discusses future options for research and management. To date, research suggests a general increase in area burned and fire occurrence but there is a lot of spatial variability, with some areas of no change or even decreases in area burned and occurrence. Fire seasons are lengthening for temperate and boreal regions and this trend should continue in a warmer world. Future trends of fire severity and intensity are difficult to determine owing to the complex and non-linear interactions between weather, vegetation and people. Improved fire data are required along with continued global studies that dynamically include weather, vegetation, people, and other disturbances. Lastly, we need more research on the role of policy, practices and human behaviour because most of the global fire activity is directly attributable to people.
1,177 citations
Cites background from "Spatial patterns and fire response ..."
...2003; Cochrane 2003), promoted by recent drought and expectations that drought conditions will continue in the future (Aragão et al. 2007)....
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...…tropical forest that has rarely burned in the past are coaxed to burn for land-clearing, leading to grazing and croplands (Nepstad et al. 1999; Cardoso et al. 2003; Cochrane 2003), promoted by recent drought and expectations that drought conditions will continue in the future (Aragão et al. 2007)....
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References
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01 Jan 2004
1,281 citations
"Spatial patterns and fire response ..." refers methods in this paper
...…spatially detailed 1997 TRMM monthly rainfall surfaces by combining the Climate Research Unit (CRU TS 2.0) interpolated ground observation dataset [Mitchell et al., 2004, available at http://www.tyndall.ac.uk/publications/working_papers/ wp55.pdf], linearly resampled to 0.25 spatial resolution,…...
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...[6] As TRMM data are not available for 1997, a critical time period for droughts in Amazonia, we inferred spatially detailed 1997 TRMM monthly rainfall surfaces by combining the Climate Research Unit (CRU TS 2.0) interpolated ground observation dataset [ Mitchell et al., 2004, available at http://www.tyndall.ac.uk/publications/working_papers/ wp55.pdf], linearly resampled to 0.25 spatial resolution, and the TRMM mean rainfall data....
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TL;DR: It is reported that protected areas in the Amazon basin—the central feature of prevailing conservation approaches—are an important but insufficient component of this strategy, based on policy-sensitive simulations of future deforestation.
Abstract: Deforestation is continuing in the Amazon basin as the cattle and soy industries expand. The main conservation policy there involves ‘protected areas’: areas designated by national governments that are left undisturbed to allow natural vegetation to develop. But this alone may not protect the rainforest ecosystem from collapse. An new estimate of forest losses made using the SimAmazonia 1 computer model suggests that by 2050, agricultural expansion will eliminate two-thirds of the forest cover of five major watersheds and ten ecoregions. One in four mammalian species examined will lose 40% of their forest habitat. Although an improved network of protected areas could avoid up to a third of projected forest loss, forest conservation on private properties will be essential if the Amazon landscapes and watersheds are to be maintained. Expansion of the cattle and soy industries in the Amazon basin has increased deforestation rates and will soon push all-weather highways into the region's core1,2,3,4. In the face of this growing pressure, a comprehensive conservation strategy for the Amazon basin should protect its watersheds, the full range of species and ecosystem diversity, and the stability of regional climates. Here we report that protected areas in the Amazon basin—the central feature of prevailing conservation approaches5,6,7,8—are an important but insufficient component of this strategy, based on policy-sensitive simulations of future deforestation. By 2050, current trends in agricultural expansion will eliminate a total of 40% of Amazon forests, including at least two-thirds of the forest cover of six major watersheds and 12 ecoregions, releasing 32 ± 8 Pg of carbon to the atmosphere. One-quarter of the 382 mammalian species examined will lose more than 40% of the forest within their Amazon ranges. Although an expanded and enforced network of protected areas could avoid as much as one-third of this projected forest loss, conservation on private lands is also essential. Expanding market pressures for sound land management and prevention of forest clearing on lands unsuitable for agriculture are critical ingredients of a strategy for comprehensive conservation3,4.
1,201 citations
"Spatial patterns and fire response ..." refers background in this paper
...This situation would be particularly exacerbated by the expansion of fire ignition sources, such as the planned Brazil-Peru connecting highway in SW Amazonia [Soares-Filho et al., 2006]....
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01 Jan 2002
TL;DR: In this paper, the effects of fire in the Amazon have been investigated and the authors found that forest fires create positive feedbacks in future fire susceptibility, fuel loading, and fire intensity.
Abstract: The incidence and importance of fire in the Amazon have increased substantially during the past decade, but the effects of this disturbance force are still poorly understood. The forest fire dynamics in two regions of the eastern Amazon were studied. Accidental fires have affected nearly 50 percent of the remaining forests and have caused more deforestation than has intentional clearing in recent years. Forest fires create positive feedbacks in future fire susceptibility, fuel loading, and fire intensity. Unless current land use and fire use practices are changed, fire has the potential to transform large areas of tropical forest into scrub or savanna.
786 citations
TL;DR: The forest fire dynamics in two regions of the eastern Amazon were studied and found that forest fires create positive feedbacks in future fire susceptibility, fuel loading, and fire intensity.
Abstract: The incidence and importance of fire in the Amazon have increased substantially during the past decade, but the effects of this disturbance force are still poorly understood. The forest fire dynamics in two regions of the eastern Amazon were studied. Accidental fires have affected nearly 50 percent of the remaining forests and have caused more deforestation than has intentional clearing in recent years. Forest fires create positive feedbacks in future fire susceptibility, fuel loading, and fire intensity. Unless current land use and fire use practices are changed, fire has the potential to transform large areas of tropical forest into scrub or savanna.
774 citations
"Spatial patterns and fire response ..." refers background in this paper
...These burnt forests are likely to be much more vulnerable to further burns if the drought were to reoccur soon [Cochrane et al., 1999]....
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...These conditions associated with intense forest degradation by logging and deforestation can dramatically increase the risk of fires [Cochrane et al., 1999]....
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TL;DR: An analysis of the mean climate and climatic trends of tropical rainforest regions over the period 1960-1998, with the aid of explicit maps of forest cover and climatological databases, finds the El Niño-Southern Oscillation is the primary driver of temperature variations across the tropics and of precipitation fluctuations for large areas of the Americas and southeast Asia.
Abstract: We present an analysis of the mean climate and climatic trends of tropical rainforest regions over the period 1960-1998, with the aid of explicit maps of forest cover and climatological databases. Until the mid-1970s most regions showed little trend in temperature, and the western Amazon experienced a net cooling probably associated with an interdecadal oscillation. Since the mid-1970s, all tropical rainforest regions have experienced a strong warming at a mean rate of 0.26 +/- 0.05 degrees C per decade, in synchrony with a global rise in temperature that has been attributed to the anthropogenic greenhouse effect. Over the study period, precipitation appears to have declined in tropical rainforest regions at a rate of 1.0 +/- 0.8% per decade (p < 5%), declining sharply in northern tropical Africa (at 3-4% per decade), declining marginally in tropical Asia and showing no significant trend in Amazonia. There is no evidence so far of a decline in precipitation in eastern Amazonia, a region thought vulnerable to climate-change-induced drying. The strong drying trend in Africa suggests that this should be a priority study region for understanding the impact of drought on tropical rainforests. We develop and use a dry-season index to study variations in the length and intensity of the dry season. Only African and Indian tropical rainforests appear to have seen a significant increase in dry-season intensity. In terms of interannual variability, the El Nino-Southern Oscillation (ENSO) is the primary driver of temperature variations across the tropics and of precipitation fluctuations for large areas of the Americas and southeast Asia. The relation between ENSO and tropical African precipitation appears less direct.
699 citations
"Spatial patterns and fire response ..." refers background in this paper
...El Niño-caused rainfall anomalies tend to be focussed on northern Amazonia [Malhi and Wright, 2004; Marengo et al., 2007]....
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