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The complete or partial collapse of the forests of Amazonia is consistently named as one of the top ten possible tipping points of Planet Earth in a changing climate. However, apart from a few observational studies that showed increased mortality after the severe droughts of 2005 and 2010, the evidence for such collapse depends primarily on modelling. Such studies are notoriously deficient at predicting the rainfall in the Amazon basin and how the vegetation interacts with the rainfall is poorly represented. Here, we use long-term surface-based observations of the air temperature and rainfall in Amazonia to provide a constraint on the modelled sensitivity of temperature to changes in precipitation. This emergent constraint also allows us to significantly constrain the likelihood of a forest collapse or dieback. We conclude that Amazon dieback under IPCC scenario RCP8.5 (crossing the tipping point) is not likely to occur in the twenty-first century.

Land use change and deforestation can influence local temperature and climate. Here we use a coupled ocean-atmosphere model to assess the impact of savannization of the Amazon Basin on the wet-bulb globe temperature heat stress index under two climate change scenarios (RCP4.5 and RCP8.5). We find that heat stress exposure due to deforestation was comparable to the effect of climate change under RCP8.5. Our findings suggest that heat stress index could exceed the human adaptation limit by 2100 under the combined effects of Amazon savannization and climate change. Moreover, we find that risk of heat stress exposure was highest in Northern Brazil and among the most socially vulnerable. We suggest that by 2100, savannization of the Amazon will lead to more than 11 million people will be exposed heat stress that poses an extreme risk to human health under a high emission scenario. Complete savannization of the Amazon Basin would enhance the effects of climate change on local heat exposure and pose a risk to human health, according to climate model projections.

The relationships between deforestation and non-timber forest products (NTFPs) supply chains are investigated in 532 municipalities throughout the Brazilian Amazon. The NTFP production of acai berry (Euterpe spp.), andiroba (Carapa spp.), Brazil nut (Bertholletia excelsa Bonpl.), and tonka bean (Dipteryx spp.) has reduced with increasing deforestation rates (p

Under the Amazon Third Way paradigm and its implementation strategy Amazon 4.0 the Amazon Creative Labs (ACL) were conceived, as a tool for training and for testing proposed concepts. Amazon 4.0 is an attempt to show that it is possible to achieve a stage of high human development combined with valuing of tropical forest through knowledge. This study demonstrates how to add value to value chains of the immense Amazon biodiversity and how to enable Amazonian populations to master bio-industrialization technologies of forest assets. The following example deals with the potential to develop bio-industries in the value chain of two forest products with high potential: cupuaçu and cocoa through the development of the so-called ACL. This will serve as an important experiment to guide several proposals being elaborated by the Scientific Panel for the Amazon.

Climate change effects can have significant impacts worldwide. Extreme events can modify water availability and agricultural production, making climate change planning an essential task. The National Institute for Space Research (INPE in Portuguese) in Brazil has made a large dataset of regional climate model outputs (simulations and projections) available, which opens up many possibilities of carrying out high-resolution climate change studies. However, there is still no performance evaluation of the model-derived rainfall output against high-resolution ground-based observation data considering the Brazilian biomes. This paper attempts to fill this gap and evaluates the simulated precipitation throughout Brazil. We used gridded observed precipitation data and historical climate simulations from the Model for Interdisciplinary Research on Climate, version 5 (MIROC5) and from the Hadley Center Global Environment Model, version 2 (HadGEM2-ES), which were downscaled by the Eta RCM (Regional Climate Model). For the overlapping period (1980–2005), there is good agreement (PBIAS up to 10%) of downscaled annual simulations for the Amazon and Cerrado biomes and large biases (reaching 40%) in the Pampa biome, compared to the observations. Our results showed that HadGEM2-ES is capable of representing long-term mean monthly precipitation for large areas well, such as the Amazon and Cerrado. Furthermore, the Eta RCM has considerably improved the driving GCM MIROC5 simulations. In conclusion, we recommend using the HadGEM2-ES simulations for the Amazon, Eta/HadGEM2-ES for the Atlantic Forest, Cerrado, and Pampa, and Eta/MIROC5 for the Caatinga and Pantanal. Our study provides an overview of two downscaled simulation datasets in Brazil that may help verify the models' suitability for further climate change assessments.

Forest degradation is widespread around the world, due to multiple factors such as unsustainable logging, agriculture, invasive species, fire, fuelwood gathering, and livestock grazing. In the Brazilian Amazon forest degradation from August 2006 to July 2016 reached 1,1 869 800 ha. The processes of forest degradation are still poorly understood, being a missing component in anthropogenic CO2 emission estimates in tropical forests. In this work, we analyzed temporal trajectories of forest degradation from August 2006 to July 2016 in the Brazilian Amazon and assessed their impact on the regional carbon balance. We combined the degradation process with deforestation-related processes (clear-cut deforestation and secondary vegetation dynamics), using the spatially-explicit INPE-EM carbon emission model. The trajectory analysis showed that 13% of the degraded area ended up being cleared and converted in the period and 61% of the total degraded area experienced only one event of degradation throughout the whole period. Net emissions added up to 5.4 GtCO2, considering the emissions from forest degradation and deforestation, absorption from degraded forest recovery, and secondary vegetation dynamics. The results show an increase in the contribution of forest degradation to net emissions towards the end of the period, related to the decrease in clear-cut deforestation rates, decoupled from the forest degradation rates. The analysis also indicates that the regeneration of degraded forests absorbed 1.8 GtCO2 from August 2006 and July 2016—a component typically overlooked in the regional carbon balance.

EnglishThe raging fires that have devastated broad swathes of the Amazonian forest this past summer have reminded the public of the vulnerability of that region to climate hazards (droughts and subsequent risks of fire) and to the—at times reprehensible—intentions of some Brazilian economic actors (whose short-term interests and activities require continued deforestation). Moving beyond the international reactions these have provoked, Futuribles proposes to report here on an initiative by a group of Brazilians who are proposing a ‘third way’ for the Amazon, combining the region’s assets in terms of biodiversity with the technological advances of ‘industry 4.0’. Ismael and Carlos Nobre, who advocate this ‘Amazon 4.0’ project, outline the potential that Brazil’s Amazonian region offers and present various possible paths for the development and expansion of the Brazilian economy on the basis of these assets. Their project is based on combining the natural wealth of the Amazonian environment with traditional forms of knowledge and cutting-edge technologies (biotech, digital, artificial intelligence etc.). Will Brazil’s current government be willing to listen? francaisLes violents incendies qui ont devaste de larges zones de la foret amazonienne cet ete 2019 ont rappele a l’opinion publique la vulnerabilite de cette region a la fois aux aleas climatiques (secheresse et risques d’incendie subsequents) et aux intentions parfois peu louables de certains acteurs economiques bresiliens (dont les activites et interets a court terme necessitent la poursuite de la deforestation). Au-dela des reactions internationales qu’ils ont suscitees, Futuribles propose ici de relayer l’initiative d’acteurs bresiliens proposant une « troisieme voie » pour l’Amazonie, alliant les atouts de la biodiversite de la region aux evolutions technologiques de l’« industrie 4.0 ». Ismael Nobre et Carlos Nobre, qui defendent ce projet « Amazonie 4.0 » presentent le potentiel qu’offre la region amazonienne au Bresil, et diverses voies de developpement et mise en valeur possibles pour l’economie bresilienne a partir de ces atouts. Leur projet repose sur une alliance des richesses naturelles du milieu amazonien, des connaissances traditionnelles et des technologies de pointe (biotechnologies, numerique, intelligence artificielle…). Sera-t-il entendu par le gouvernement en place ?

During most of the rainy season in 2014, the Southeast of Brazil – including the Cantareira reservoir system – received below-normal rainfall. The main cause leading to that heavy lack of rain was an intense, persistent and anomalous highpressure system blocking moisture flow from the Amazon and the development and passage of cold front systems and the South Atlantic Convergence Zone, which are responsible for rainfall in this region during summer. This blocking system lasted for 45 days, which is extremely rare. Low rainfall amounts coupled with an increased demand for water and an inefficient water management system led to the so-called “water crisis” during 2014, which extended into 2015

The contribution of coherent structures (CSs) to daytime buoyancy heat flux was calculated for three forest sites in the Amazon region and a wetland site. Ejections and sweeps had similar contributions to fluxes at all sites, and when decomposing this contribution in scales, the resulting spectra were narrower for the forests. When accounting for times scales from 10 to 200s, CSs contributed to approximately 80% of fluxes for Caxiuana forest site, with lower values for other locations. Among the forest, the contribution for the Jaru site was the lowest (≈66%) due to peak of contribution being close to 200s.

Amazon tropical forests are being replaced by pasturelands and croplands, but they sometimes revert to regrowth forest when abandoned after a period of agricultural use. Research suggests that this secondary regrowth is limited by climate and nutrient availability and, using a coupled biosphere-atmosphere model, we investigated patterns in the regrowth of the Amazon rainforest after a full deforestation event, considering different types of nutrient stress. We found that, over a 50 year regrowth period, the reduction of precipitation caused by large-scale deforestation was not sufficient to prevent secondary forest regrowth, but this decrease in precipitation combined with nutrient limitation, due to logging and frequent fires, did indeed prevent forest regrowth in central and southern Amazonia, leading to a savannization. These results are concerning, as the northern Mato Grosso region has the highest clearing rate in Amazonia. The low resilience of the forest under nutrient stress indicates that a large scale disturbance could greatly expand the area suitable for cropland, accelerating forest disappearance.

For half a century, the process of economic integration of the Amazon has been based on intensive use of renewable and nonrenewable natural resources, which has brought significant basin-wide environmental alterations. The rural development in the Amazonia pushed the agricultural frontier swiftly, resulting in widespread land-cover change, but agriculture in the Amazon has been of low productivity and unsustainable. The loss of biodiversity and continued deforestation will lead to high risks of irreversible change of its tropical forests. It has been established by modeling studies that the Amazon may have two “tipping points,” namely, temperature increase of 4 °C or deforestation exceeding 40% of the forest area. If transgressed, large-scale “savannization” of mostly southern and eastern Amazon may take place. The region has warmed about 1 °C over the last 60 y, and total deforestation is reaching 20% of the forested area. The recent significant reductions in deforestation—80% reduction in the Brazilian Amazon in the last decade—opens up opportunities for a novel sustainable development paradigm for the future of the Amazon. We argue for a new development paradigm—away from only attempting to reconcile maximizing conservation versus intensification of traditional agriculture and expansion of hydropower capacity—in which we research, develop, and scale a high-tech innovation approach that sees the Amazon as a global public good of biological assets that can enable the creation of innovative high-value products, services, and platforms through combining advanced digital, biological, and material technologies of the Fourth Industrial Revolution in progress.

It is well known that most of the severe droughts in Amazonia, such as that of 1997, are El Nino-related. However, in 2005, the Amazon was affected by a severe drought that was not El Nino-related, as most of the rainfall anomalies that have happened in southwestern Amazonia are driven by sea surface temperature anomalies in the tropical North Atlantic. Earlier studies have analyzed both droughts in terms of their meteorological causes and impacts in terra firme (non-flooded) forests. This study compares the hydrological effects of both droughts on the Amazonian floodplain and discusses their potential ecological and human impacts based on an extensive literature review. The results revealed that the effects of the 2005 drought were exacerbated because rainfall was lower and evaporation rates were higher at the peak of the dry season compared to the 1997 drought. This induced a more acute depletion of water levels in floodplain lakes and was most likely associated with higher fish mortality rates. Based on the fact that the stem growth of many floodplain species is related to the length of the non-flooded period, it is hypothesized that the 1997 drought had more positive effects on floodplain forest growth than the 2005 drought. The fishing community of Silves in central Amazonia considered both droughts to have been equally severe. However, the 2005 drought was widely broadcasted by the press; therefore, the governmental mitigation efforts were more comprehensive. It is suggested that the availability of new communication technology and greater public awareness regarding environmental issues, combined with the new legal framework for assessing the severity of calamities in Brazil, are among the primary factors that explain the difference in societal response between the two droughts.

The study estimated, for the first time, the greenhouse gas emissions associated with cattle raising in Brazil, focusing on the period from 2003 to 2008 and the three principal sources: 1) portion of deforestation resulting in pasture establishment and subsequent burning of felled vegetation; 2) pasture burning; and 3) bovine enteric fermentation. Deforestation for pasture establishment was only considered for the Amazon and Cerrado. Emissions from pasture burning and enteric fermentation were accounted for the entire country. The consolidated emissions estimate lies between approximately 813 Mt CO2eq in 2008 (smallest value) and approximately 1,090 Mt CO2eq in 2003 (greatest value). The total emissions associated with Amazon cattle ranching ranged from 499 to 775 Mt CO2eq, that of the Cerrado from 229 to 231 Mt CO2eq, and that of the rest of the country between 84 and 87 Mt CO2eq. The full set of emissions originating from cattle raising is responsible for approximately half of all Brazilian emissions (estimated to be approximately 1,055 Mt CO2eq in 2005), even without considering cattle related sources not explicitly estimated in this study, such as energy use for transport and refrigeration along the beef and derivatives supply chain. The potential for reduction of greenhouse gas emissions offered by the Brazilian cattle industry is very high and might constitute Brazil’s most important opportunity for emissions mitigation. The study offers a series of policy recommendations for mitigation that can be implemented by public and private administrators at a low cost relative to other greenhouse gas reduction options.

This is an observational study of the large-scale moisture transport over South America, with some analyses on its relation to subtropical rainfall. The concept of aerial rivers is proposed as a framework: it is an analogy between the main pathways of moisture flow in the atmosphere and surface rivers. Opposite to surface rivers, aerial rivers gain (lose) water through evaporation (precipitation). The magnitude of the vertically integrated moisture transport is discharge, and precipitable water is like the mass of the liquid column—multiplied by an equivalent speed it gives discharge. Trade wind flow into Amazonia, and the north/northwesterly flow to the subtropics, east of the Andes, are aerial rivers. Aerial lakes are the sections of a moisture pathway where the flow slows down and broadens, because of diffluence, and becomes deeper, with higher precipitable water. This is the case over Amazonia, downstream of the trade wind confluence. In the dry season, moisture from the aerial lake is transported northeastward, but weaker flow over southern Amazonia heads southward toward the subtropics. Southern Amazonia appears as a source of moisture to this flow. Aerial river discharge to the subtropics is comparable to that of the Amazon River. The variations of the amount of moisture coming from Amazonia have an important effect over the variability of discharge. Correlations between the flow from Amazonia and subtropical rainfall are not strong. However, some months within the set of dry seasons observed showed a strong increase (decrease) occurring together with an important increase (decrease) in subtropical rainfall.

The Amazon has a well-defined wet austral summer monsoon and dry winter monsoon precipitation regime and experienced a sequence of drought events in the last 13 years. This study performs a comparative assessment of observed and predicted climate conditions during the three most recent drought events in the Amazon, in 1997–1998, 2004–2005 and 2009–2010, with emphasis on how these events affected the regional monsoon-like precipitation regime. A century long Negro River level time series at Manaus is investigated, applying extreme values theory for estimating return periods of these major drought events. Possible teleconnections of river levels at Manaus and sea surface temperature at remote regions are explored. Large scale oceanic and atmospheric conditions are investigated to highlight the mechanisms associated with the observed drought conditions, particularly during the dry monsoon season. Satellite estimates are used for diagnosing biomass burning aerosol and discuss possible contributions to the observed precipitation deficits in the 2005 and 2010 drought events during the dry monsoon season. The study is concluded with an analysis of the performance of seasonal precipitation predictions for the dry monsoon seasons of July to September 1998, 2005 and 2010 produced with the operational seasonal prediction system used at the Center for Weather Forecasts and Climate Studies (CPTEC) of the Brazilian National Institute for Space Research (INPE). This system was capable of producing 1 month in advance drought warning for the three investigated events, relevant for helping the government and local population make decisions for reducing drought impacts in the Amazon region. Copyright © 2012 Royal Meteorological Society

We present a generic spatially explicit modeling framework to estimate carbon emissions from deforestation (INPE-EM). The framework incorporates the temporal dynamics related to the deforestation process and accounts for the biophysical and socioeconomic heterogeneity of the region under study. We build an emission model for the Brazilian Amazon combining annual maps of new clearings, four maps of biomass, and a set of alternative parameters based on the recent literature. The most important results are as follows: (a) Using different biomass maps leads to large differences in estimates of emission; for the entire region of the Brazilian Amazon in the last decade, emission estimates of primary forest deforestation range from 0.21 to 0.26 Pg C yr � 1 . (b) Secondary vegetation growth presents a small impact on emission balance because of the short duration of secondary vegetation. In average, the balance is only 5% smaller than the primary forest deforestation emissions. (c) Deforestation rates decreased significantly in the Brazilian Amazon in recent years, from 27 Mkm 2 in 2004 to 7 Mkm 2 in 2010. INPE-EM process-based estimates reflect this decrease even though the agricultural frontier is moving to areas of higher biomass. The decrease is slower than a non-process instantaneous model would estimate as it considers residual emissions (slash, wood products, and secondary vegetation). The average balance, considering all biomass, decreases from 0.28 in 2004 to 0.15 Pg C yr � 1 in 2009; the nonprocess model estimates a decrease from 0.33 to 0.10 Pg C yr � 1 . We conclude that the INPE-EM is a powerful tool for representing deforestation-driven carbon emissions. Biomass estimates are still the largest source of uncertainty in the effective use of this type of model for informing mechanisms such as REDD+. The results also indicate that efforts to reduce emissions should focus not only on controlling primary forest deforestation but also on creating incentives for the restoration of secondary forests.

During 2009 the Amazon basin was hit by a heavy flooding with a magnitude and duration few times observed in several decades. Torrential rain in northern and eastern Amazonia during the austral summer of 2008–2009 swelled the Amazon River and its tributaries. By July 2009, water levels of the Rio Negro, a major Amazon tributary, reached at Manaus harbor a new record, the highest mark of the last 107 years. During the 2008–2009 hydrological year, the rainy season on northern and northwestern Amazonia started prematurely, and was followed by a longer-than-normal rainy season. An anomalously southward migration of the ITCZ during May–June 2009, due to the warmer than normal surface waters in the tropical South Atlantic, was responsible for abundant rainfall in large regions of eastern Amazonia and Northeast Brazil from May to July 2009. We also compared the flood of 2009 with other major events recorded in 1989 and 1999. The hydrological consequences of this pattern were earlier than normal floods in Amazon northern tributaries, which peak discharges at their confluences with the main stem almost coincided with the peaks of southern tributaries. Since the time displacement of the contribution to the main stem of northern and southern Amazon tributaries is fundamental for damping flood waves in the main stem, the simultaneous combinations of peak discharges of tributaries resulted in an extreme flood.

The climatic effects of concurrent land-cover changes in Amazonia and Northeast Brazil (NEB) were evaluated by simulations using the Center for Weather Forecasting and Climate Studies Atmospheric General Circulation Model (CPTEC-AGCM). Three experiments were performed: Amazon savannization, NEB desertification and both land-cover changes occurring concurrently. We found that land-cover change from adjacent areas do affect both Amazon and NEB regions and that the negative precipitation anomaly in NEB due to concurrent land-cover changes in Amazon and NEB is weaker than the linear addition of the anomalies considering the land-cover changes separately (synergistic behaviour). A simple mechanism was proposed to explain this behaviour. Copyright © 2011 Royal Meteorological Society

The stability of the Amazon forest–climate equilibrium is being perturbed by a number of human drivers of change (e.g. deforestation, global warming, forest fires, higher CO2 concentrations, and increased frequency of droughts and floods). Quantitative assessments for the maintenance of the tropical forest indicate that ‘tipping points’ may exist for total deforested area (>40%) and for global warming (ΔT > 3–4°C). The likelihood of exceeding a tipping point can be greatly exacerbated by increases in forest fires and droughts, but quantification of those effects is still lacking. Forest resilience can be significantly increased if CO2 ‘fertilization’ effect is proven to be taking place for tropical forests, but it can be offset by continued increases in temperature, rainfall seasonality, and forest fires.

Biome models of the global climate-vegetation relationships indicate that most of the Brazilian Amazon has potential for being covered by tropical forests. From current land-use processes observed in the region, however, substantial deforestation and fire activity have been verified in large portions of the region, particularly along the Arc of Deforestation. In a first attempt to evaluate the long-term potential for tropical-forest degradation due to deforestation and fires in the Brazilian Amazon, we analysed large-scale data on fire activity and climate factors that drive the distribution of tropical forests in the region. The initial analyses and results from this study lead to important details on the relations between these quantities and have important implications for building future parameterizations of the vulnerability of tropical forests in the region.

In 2005, southwestern Amazonia experienced the effects of an intense drought that affected life and biodiversity. Several major tributaries as well as parts of the main river itself contained only a fraction of their normal volumes of water, and lakes were drying up. The consequences for local people, animals and the forest itself are impossible to estimate now, but they are likely to be serious. The analyses indicate that the drought was manifested as weak peak river season during autumn to winter as a consequence of a weak summertime season in southwestern Amazonia; the winter season was also accompanied by rainfall that sometimes reached 25% of the climatic value, being anomalously warm and dry and helping in the propagation of fires. Analyses of climatic and hydrological records in Amazonia suggest a broad consensus that the 2005 drought was linked not to El Niño as with most previous droughts in the Amazon, but to warming sea surface temperatures in the tropical North Atlantic Ocean.

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.

The Large-Scale Biosphere–Atmosphere Experiment in Amazonia (LBA) is a multi-year Brazil-led international environmental science experiment funded by the U.S. National Aeronautics Space Administration, the European Union and Brazil. It is intended to inform decision making under the United Nations Framework Convention on Climate Change (UNFCCC) as well as Brazilian national environmental decision-making related to the Amazon region. Focused on the Amazon region, and primarily on the Brazilian Amazon, the LBA is a case study in issues that can arise when doing globally oriented research in a less developed country setting and a test of assumptions that such research simultaneously benefits global and local levels. This article offers a qualitative evaluation of the extent to which the LBA has achieved its goals and identifies structural obstacles within science that must be overcome to improve the fit between international science programs and efforts to nurture more sustainable use of natural resources in a less developed country.

The coupling between different types of surface (tropical forest or grass) and the Convective Boundary Layer(CBL) has been investigated using observational (rawinsoundings) data collected over Rondônia in southwest Amazonia. The data reported here support the notion that deforestation may modify the dynamics of the boundary layer, in particular during the dry season. In this period the sensible heat fluxes are very high over pasture, creating a CBL around 550 m deeper compared to that over the forest. The measurements showed the height of the fully developed CBL for pasture to be 1650 m, compared to around 1100 m for forest. During the wet season the height of the CBL is lower than during the dry season and has the same height (around 1000 m) for forest and pasture sites. The CBL over pasture is hotter and drier than over forest during the dry season, but during the wet season the air temperatures and humidities are similar. Comparing the CBL growth during the dry and wet season, there is evidence that the CBL properties over the forest are not dependent on the surface characteristics, but over the pasture they are. © Springer-Verlag 2004.

The distribution of sources and sinks of carbon among the world's ecosystems is uncertain. Some analyses show northern mid-latitude lands to be a large sink, whereas the tropics are a net source; other analyses show the tropics to be nearly neutral, whereas northern mid-latitudes are a small sink. Here we show that the annual flux of carbon from deforestation and abandonment of agricultural lands in the Brazilian Amazon was a source of about 0.2 Pg Cyr(-1) over the period 1989-1998 (1 Pg is 10(15) g). This estimate is based on annual rates of deforestation and spatially detailed estimates of deforestation, regrowing forests and biomass. Logging may add another 5-10% to this estimate, and fires may double the magnitude of the source in years following a drought. The annual source of carbon from land-use change and fire approximately offsets the sink calculated for natural ecosystems in the region. Thus this large area of tropical forest is nearly balanced with respect to carbon, but has an interannual variability of +/- 0.2 PgC yr(-1).

Amazonian deforestation rates are used to determine human effects on the global carbon cycle1,2,3 and to measure Brazil's progress in curbing forest impoverishment1,4,5. But this widely used measure of tropical land use tells only part of the story. Here we present field surveys of wood mills and forest burning across Brazilian Amazonia which show that logging crews severely damage 10,000 to 15,000 km2 yr−1 of forest that are not included in deforestation mapping programmes. Moreover, we find that surface fires burn additional large areas of standing forest, the destruction of which is normally not documented. Forest impoverishment due to such fires may increase dramatically when severe droughts provoke forest leaf-shedding and greater flammability; our regional water-balance model indicates that an estimated 270,000 km2 of forest became vulnerable to fire in the 1998 dry season. Overall, we find that present estimates of annual deforestation for Brazilian Amazonia capture less than half of the forest area that is impoverished each year, and even less during years of severe drought. Both logging and fire increase forest vulnerability to future burning6,7 and release forest carbon stocks to the atmosphere, potentially doubling net carbon emissions from regional land-use during severe El Nino episodes. If this forest impoverishment is to be controlled, then logging activities need to be restricted or replaced with low-impact timber harvest techniques, and more effective strategies to prevent accidental forest fires need to be implemented.

Meteorological observations from the Anglo-Brazilian Amazonian Climate Observation Study (ABRACOS), together with the global reanalysis from the National Center for Environmental Prediction (NCEP) and satellite images, have been used to study the spatial extent and intensity of cold surges (known locally as ''friagens'') in the Amazon basin. Case studies are presented of two of the strongest events of the 1994 winter season: 26 June and 10 July 1994. In both events, daily minimum temperatures in southeastern Brazil dropped to near or below 08C, while at the same time minimum temperatures in southern Amazonia (Ji-Paranasite) were almost 88C below average. Air temperature and humidity also fell in central and western Amazonia (Manaus and Maraba ´ sites, respectively), although the fact that these reductions were less substantial than those farther to the south indicates that the cold air is greatly modified as it moves across Amazonia. In Ji-Paranathe largest drops in minimum temperature coincided with strong winds from the south, implying that cold advection was the main mechanism for the falling temperatures. In contrast, there was no increase in wind speed at Manaus and Marabaduring the days with reduced temperatures. At these sites, cooling was due to a reduction of the maximum temperature caused, at least partially, by increased cloudiness rather than by a lowering of minimum temperatures as at Ji-Parana ´. With regard to the depth of the atmospheric boundary layer (ABL), it is observed that during the passage of the cold air in southern Amazonia, the ABL was cooler and shallower than during the pre- and postfriagem days. The friagens presented are of 5- to 6-day duration, including the passage of the cold front, but the period with cold temperatures lasts between 2 and 3 days.

Surface parameter digital maps of vegetation, soil, and relief are obtained over Rondonia, Brazil, covering the 5° × 5° region 8°–13°S, 65°–60°W. Numerical maps of the natural landscape structure have been achieved by digitizing existing 1:1 000 000 paper maps. Satellite data give information about the most recent modifications of the surface due to human activities. This mapping work is the first step of a mesoscale meteorological modeling program.

To the extent that many studies of the last two decades deepen the understanding about the Amazon tropical forest and more is known about the environmental services it offers, they also increased our level of awareness about the growing threats that this system has been subjected to. In addition to the process of uncontrolled expansion of the agriculture frontier, the Amazon, for its large scale, is an ecosystem highly susceptible to climate at regional and global scales. In this chapter we address issues related to environmental drivers of change in the Amazon: deforestation, climate, climate extremes, and fire. The goal is to present aspects of a synergistic action of these effects and the possible responses of Amazonian ecosystems to these drivers of change: (1) short-term responses as the mortality of some species (biodiversity loss), loss of living biomass with consequent influence on storage, and exchanges of carbon with the atmosphere to (2) long-term responses, such as ‘savannization’ and Amazon dieback. On the other hand, it has been hypothesized that the forest may show some degree of resilience to tolerate those impacts before starting to respond with degradation of the ecosystems. One of the challenges of Amazonian science today is to find out how close those drivers might be from exceeding ‘tipping points’ of stability of the Amazonian system.

The environmental conditions associated with squall lines (SL) that were observed during the period of 13 April–13 May 1987 (GTE/ABLE-2B) originating at the northern coast of South America and propagating over the Amazon Basin are documented. The SL observed on 5–7 May are examined in more detail. The SL days had in common a stronger and deeper low-level jet when compared with the days without SL. Two possible explanations are found for the intensification of the low-level jet: propagating easterly waves in the tropical Atlantic, which eventually reach Manaus, and localized heat sources in the western Amazon. Both were observed on 5–6 May. It is suggested that numerical simulations should be performed to unravel the relative importance of each large-scale mechanism.

The Amazon River system is the single, largest source of freshwater on Earth and its flow regime is subject to interannual and long-term climate variability, which translate into large variations in downstream discharge (Richey et al., 1989; Marengo and Nobre, 2001; Marengo 2004, 2005, 2006, 2007; Milly et al., 2005, Marengo et al., 2008a, b; Cox et al., 2008; Zeng et al., 2008). To predict future climate (rainfall) change and consequent river variability an understanding of the physical mechanisms related to regional and large-scale atmospheric–oceanic–biospheric forcings is required. The temporal and spatial nature and impact of any variability in the hydrometeorology of the Amazon Basin must be considered in this context.

[1] We examine potential critical thresholds for biome shift in the Amazonian tropical forest by forcing a potential vegetation model with prescribed climate anomalies and projections from global and regional climate models and different levels of CO2 fertilization effect under the SRES A2 scenario (2070–2099). The results indicate that tropical forests might be replaced by seasonal forests or savanna over eastern Amazonia with temperature increases of 2–3°C (4–5°C), when CO2 fertilization effect is not considered (partially considered), depending on precipitation anomaly. A precipitation decrease greater than 30% would trigger the shift from tropical forest to drier biomes, such as savanna and shrubland in southeastern Amazonia. The projected decrease in precipitation during the dry season and the increase of temperature are the main mechanisms driving calculated biome changes. However, biome changes are considerably smaller when the optimum fertilization effect is included.

the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) has resulted in an unprecedented international effort to understand the functioning of the vegetation of Amazonia and its interaction with the atmosphere and hydrosphere. As a result, Amazonia is now almost certainly the best studied major tropical forest region of the world, although our journey to a comprehensive understanding of the functioning of this system is only just beginning. Some of the key questions that LBA asked in relation to the vegetation and soils of Amazonia included the following: (1) How does the structure and functioning of Amazonian forests vary across the region; what factors drive this variation? (2) How much carbon is stored in Amazonian vegetation and soils; is this carbon store increasing or decreasing in response to contemporary environmental change? (3) How does the supply of nitrogen, phosphorus, and other nutrients affect Amazonian forests and the viability and sustainability of management practices after conversion of forest to other land uses? (4) How does Amazonian vegetation respond to seasonal, interannual, and long-term drought? (5) What role does Amazonia play in global climatic teleconnections and in the budgets of the major atmospheric trace gases? (6) How are Amazonian forests changing, and how will they change in response to climate change? In this introduction, we provide a brief overview of the major themes discussed in this section. We do not introduce the chapters in sequence but rather when appropriate to our narrative.

This paper reviews the experimental activity and primary results of the Amazon Region Micrometeorology Experiment (ARME), and the subsequent impact of these data in improving the prediction of post-deforestation Amazonian climate using general circulation models. It previews the new 5 year programme of collaborative Anglo-Brazilian research which will extend these studies by providing calibration of the land-atmosphere interaction for cleared forest areas, and measurements of the comparative near-surface climatology for large clearings and adjacent areas of undisturbed natural forest. Finally it overviews preliminary plans for a major international study in Amazonia under the World Climate Research Programme and the International Geosphere Biosphere Programme.

The Amazon rainforest plays a crucial role in the climate system, helping to drive atmospheric circulations in the tropics by absorbing energy and recycling about half of the rainfall that falls on it. This region (Amazonia) is also estimated to contain about one-tenth of the total carbon stored in land ecosystems, and to account for one-tenth of global, net primary productivity. The resilience of the forest to the combined pressures of deforestation and global warming is therefore of great concern, especially as some general circulation models (GCMs) predict a severe drying of Amazonia in the twenty-first century. Here we analyse these climate projections with reference to the 2005 drought in western Amazonia, which was associated with unusually warm North Atlantic sea surface temperatures (SSTs). We show that reduction of dry-season (July–October) rainfall in western Amazonia correlates well with an index of the north–south SST gradient across the equatorial Atlantic (the 'Atlantic N–S gradient'). Our climate model is unusual among current GCMs in that it is able to reproduce this relationship and also the observed twentieth-century multidecadal variability in the Atlantic N–S gradient, provided that the effects of aerosols are included in the model. Simulations for the twenty-first century using the same model3, 8 show a strong tendency for the SST conditions associated with the 2005 drought to become much more common, owing to continuing reductions in reflective aerosol pollution in the Northern Hemisphere.

[1] Field observations and numerical studies revealed that large scale deforestation in Amazonia could alter the regional climate significantly, projecting a warmer and somewhat drier post-deforestation climate. In this study we employed the CPTEC-INPE AGCM to assess the effects of Amazonian deforestation on the regional climate, using simulated land cover maps from a business-as-usual scenario of future deforestation in which the rainforest was gradually replaced by degraded pasture or by soybean cropland. The results for eastern Amazonia, where changes in land cover are expected to be larger, show increase in near-surface air temperature, and decrease in evapotranspiration and precipitation, which occurs mainly during the dry season. The relationship between precipitation and deforestation shows an accelerating decrease of rainfall for increasing deforestation for both classes of land use conversions. Continued expansion of cropland in Amazonia is possible and may have important consequences for the sustainability of the region's remaining natural vegetation.

[1] Models of climate change predict close coupling between increases in aridity and conversion of Amazonian forests to savanna. Here we assess the vulnerability and resilience of Amazonian vegetation to climate change by analyzing observed climate-vegetation relationships using climate data, observed vegetation distributions, and evapotranspiration rates inferred from eddy flux data. We found that drought frequency is an excellent predictor of the forest-savanna boundary, indicating the key role of extreme climatic events for inducing vegetation change, and highlighting particularly vulnerable regions of Amazonia.

The Amazon Basin contains the largest extent of tropical forest on Earth, over 5 × 106 km2, and accounts for a large proportion of the planefs animal and plant species. It also contains over 2 × 106 km2 of savanna Vegetation to the north and to the south of the domain of the tropical forest. The annual discharge of the River Amazon into the Atlantic Ocean of more than 200 000 m3 s-1 contributes about 18% of the global flow of fresh water into the oceans. It is thought that humans have inhabited tropical South America for at least 12 000 years, but their impact on the Vegetation cover was quite small from immemorial times to about 1950. By the time the Europeans arrived in this continent 500 years ago, there were several million indigenous people living in Amazonia. Their impact on the Vegetation cover was negligible because they practised small-scale shifting and burning agriculture. Because many tribes selected useful plant species to grow near their dwellings (for instance, the Kayapo “gardening”), it is thought that the species composition and distribution have gradually changed from pre-historical times but with little overall effect on the Vegetation cover. For most of the last 500 years, the forests of Amazonia were left untouched, including the period known as the “rubber boom” (second half of the 19U1 Century to about 1910). During that period, the river System was used to bring hundreds of thousand of workers to the far-distant portions of the forest to tap the rubber tree,but land Clearing was not significant. In fact, after the demise of the rubber boom by 1910 many workers settled along the river corridors, and borrowed many of the habits from the indigenous tribes that they had displaced such as adopting small-scale shifting and burning agriculture, and having fish as their main protein source. In summary, they caused only negligible disturbance to the forest and by the 1950s only about 1% of the forest of Amazonia had been cleared.

[1] The existence of multiple climate-vegetation equilibria in Tropical South America is investigated under present-day climate conditions with the use of an atmospheric general circulation model coupled to a potential vegetation model. Two stable equilibria were found. One corresponds to the current biome distribution. The second is a new equilibrium state: savannas replace eastern Amazonian forests and a semi-desert area appears in the driest portion of Northeast Brazil. If sustainable development and conservation policies were not able to halt the increasing environmental degradation in those areas, then land use changes could, per se, tip the climate-vegetation system towards this new alternative drier stable equilibrium state, with savannization of parts of Amazonia and desertification of the driest area of Northeast Brazil, and with potential adverse impacts on the rich species diversity in the former region and water resources in the latter.

[1] This overview summarizes general Large-Scale Atmosphere-Biosphere Experiment in Amazonia (LBA) papers and highlights some of the insights gained from these investigations and needs for future research. It complements the overview of Silva Dias et al. [2002a], which summarizes the papers published on the joint major atmospheric mesoscale campaign in the wet season (WetAMC), which was held jointly in Rondonia with the Tropical Rainfall Measuring Mission (TRMM) validation campaign known as TRMM-LBA. It also complements the overview of Andreae et al. [2002], which summarizes the papers describing the biogeochemical cycling of carbon, water, energy, aerosols, and trace gases resulting from the European Studies on Trace Gases and Atmospheric Chemistry, known as LBA-EUSTACH Project. The 17 papers summarized under this part of the special issue are regrouped into three main categories: (1) measurements and data sets, (2) remote sensing, and (3) modeling.

The Amazon Basin contains a multitude of ecosystems, biological and ethnic diversity and the largest extent of tropical forest on Earth, over 5 x 106 km2, and accounts for an estimated 1/3 of the planet’s animal and plant species. Currently only a small number of species are used by man. The region is abundant in water resources. Annual rainfall is 2.3 m over the Amazon Basin, and the mean outflow of the Amazon River into the Atlantic is over 200 000 m3 s-1, which corresponds to 18% of the total flow of fresh water into the world’s oceans. The region stores over 100 Gt of carbon in vegetation and soils. However, over the past 30 years, rapid development has led to the deforestation of over 550 000 km2 in Brazil alone. Current rates of annual deforestation are in the range of 15 000 km2 to 20 000 km2 (INPE 2001), and the spatial pattern of deforestation in Brazilian Amazonia up to 1997 is illustrated in Fig. 26.1.

A rare drought in the Amazon culminated in 2005, leading to near record-low streamflows, small Amazon river plume, and greatly enhanced fire frequency. This episode was caused by the combination of 2002-03 El Nino and a dry spell in 2005 attributable to a warm subtropical North Atlantic Ocean. Analysis for 1979-2005 reveals that the Atlantic influence is comparable to the better-known Pacific linkage. While the Pacific influence is typically locked to the wet season, the 2005 Atlantic impact concentrated in the Amazon dry season when its hydroecosystem is most vulnerable. Such mechanisms may have wide-ranging implications for the future of the Amazon rainforest. S Supplementary data are available from stacks.iop.org/ERL/3/014002

"A coupled numerical model of the global atmosphere and biosphere has been used to assess the effects of Amazon deforestation on the regional and global climate. When the tropical forests in the model were replaced by degraded grass (pasture), there was a significant increase in surface temperature and a decrease in evapotranspiration and precipitation over Amazonia. In the simulation, the length of the dry season also increased; such an increase could make reestablishment of the tropical forests after massive deforestation particularly difficult."

The Amazon region contains the largest area of tropical forest on Earth, over 5×106 km2. While the bulk of the region remains forested, rapid development has led to the destruction of over 500,000 km2 of forest in Brazil alone over the past 25 years [Houghton et al., 2000].