Explore the vast range of titles available.

The Amazon basin is a key component of the global carbon cycle. The old-growth rainforests in the basin represent storage of ~ 120 petagrams of carbon (Pg C) in their biomass. Annually, these tropical forests process approximately 18 Pg C through respiration and photosynthesis. This is more than twice the rate of global anthropogenic fossil fuel emissions. The basin is also the largest global repository of biodiversity and produces about 20 percent of the world's flow of fresh water into the oceans. Despite the large carbon dioxide (CO2) efflux from recent deforestation, the Amazon rainforest ecosystem is still considered to be a net carbon sinks of 0.8-1.1 Pg C per year because growth on average exceeds mortality (Phillips et al. 2008). However, current climate trends and human-induced deforestation may be transforming forest structure and behavior (Phillips et al. 2009). Increasing temperatures may accelerate respiration rates and thus carbon emissions from soils (Malhi and Grace 2000). High probabilities for modification in rainfall patterns (Malhi et al. 2008) and prolonged drought stress may lead to reductions in biomass density. Resulting changes in evapo-transpiration and therefore convective precipitation could further accelerate drought conditions and destabilize the tropical ecosystem as a whole, causing a reduction in its biomass carrying capacity or dieback. In turn, changes in the structure of the Amazon and its associated water cycle will have implications for the many endemic species it contains and result in changes at a continental scale. Clearly, with much at stake, if climate-induced damage alters the state of the Amazon ecosystem, there is a need to better understand its risk, process, and dynamics. The objective of this study is to assist in understanding the risk, process, and dynamics of potential Amazon dieback and its implications.

Heat waves in Amazonia have become more frequent, longer, and more intense according to observational records. Climate change and deforestation are two significant drivers of such trends. In the Amazon rainforest, heat waves are still an understudied issue, in part due to limited surface observations. To date, heat waves in central Amazon have been associated with the ITCZ northward migration in austral winter, weakening moisture influx through the South American Monsoon System. This study contributes to this topic by being the first Amazon-specific analysis of heat extremes and the first in South America to jointly explore extreme heat wave events and associated synoptic atmospheric and land surface conditions. Ten of the most extreme heat waves are identified in the Southeast of Amazonia, from Era-Interim (1979 to 2018) maximum daily temperature records. Dry conditions are measured from relative humidity and evaporative fraction anomalies at surface and vertically also using the Era-Interim data. In all 10 events an extreme drying signal co-occurs with extreme heat waves. Wind patterns and anomalies revealed a consistent easterly dry advection anomalously extending to Southeast Amazonia. In addition, an intensification of the northerly South Atlantic Anticyclone wind circulation reduced the influx of moisture to Southeast Amazon, namely linked to the South American Low Level Jet. These, together, contributed to a compound effect on the extreme heat waves under near-surface drying conditions, which escalated hot temperatures to extreme heat.

The objective of this study is to assess the climate projections over South America using the Eta-CPTEC regional model driven by four members of an ensemble of the Met Office Hadley Centre Global Coupled climate model HadCM3. The global model ensemble was run over the twenty-first century according to the SRES A1B emissions scenario, but with each member having a different climate sensitivity. The four members selected to drive the Eta-CPTEC model span the sensitivity range in the global model ensemble. The Eta-CPTEC model nested in these lateral boundary conditions was configured with a 40-km grid size and was run over 1961–1990 to represent baseline climate, and 2011–2100 to simulate possible future changes. Results presented here focus on austral summer and winter climate of 2011–2040, 2041–2070 and 2071–2100 periods, for South America and for three major river basins in Brazil. Projections of changes in upper and low-level circulation and the mean sea level pressure (SLP) fields simulate a pattern of weakening of the tropical circulation and strengthening of the subtropical circulation, marked by intensification at the surface of the Chaco Low and the subtropical highs. Strong warming (4–6°C) of continental South America increases the temperature gradient between continental South America and the South Atlantic. This leads to stronger SLP gradients between continent and oceans, and to changes in moisture transport and rainfall. Large rainfall reductions are simulated in Amazonia and Northeast Brazil (reaching up to 40%), and rainfall increases around the northern coast of Peru and Ecuador and in southeastern South America, reaching up to 30% in northern Argentina. All changes are more intense after 2040. The Precipitation–Evaporation (P–E) difference in the A1B downscaled scenario suggest water deficits and river runoff reductions in the eastern Amazon and São Francisco Basin, making these regions susceptible to drier conditions and droughts in the future.

The extent of the Amazon rainforest is projected to drastically decrease in future decades because of land-use changes. Previous climate modelling studies have found that the biogeophysical effects of future Amazonian deforestation will likely increase surface temperatures and reduce precipitation locally. However, the magnitude of these changes and the potential existence of tipping points in the underlying relationships is still highly uncertain. Using a regional climate model at a resolution of about 50 km over the South American continent, we perform four ERA-interim-driven simulations with prescribed land cover maps corresponding to present-day vegetation, two deforestation scenarios for the twenty-first century, and a totally-deforested Amazon case. In response to projected land cover changes for 2100, we find an annual mean surface temperature increase of 0.5 ∘ C over the Amazonian region and an annual mean decrease in rainfall of 0.17 mm/day compared to present-day conditions. These estimates reach 0.8 ∘ C and 0.22 mm/day in the total-deforestation case. We also compare our results to those from 28 previous (regional and global) climate modelling experiments. We show that the historical development of climate models did not modify the median estimate of the Amazonian climate sensitivity to deforestation, but led to a reduction of its uncertainty. Our results suggest that the biogeophysical effects of deforestation alone are unlikely to lead to a tipping point in the evolution of the regional climate under present-day climate conditions. However, the conducted synthesis of the literature reveals that this behaviour may be model-dependent, and the greenhouse gas-induced climate forcing and biogeochemical feedbacks should also be taken into account to fully assess the future climate of this region.

The increase in the greenhouse gas emissions leads to changes in the mechanisms connecting the two major river basins in South America, the Amazon and La Plata basins, at subcontinental scale. Studies very often neglect to address the impact of the model-component choices on the projected change in precipitation in the two river basins. Within that context, the present study investigates the probable causes of changes in the hydroclimate of the two river basins through projections from three global climate models—driven by the pathway with no stabilization of the emissions growth by 2100—with focus on the warming of regions in the equatorial Atlantic and Pacific Oceans. Because the annual cycle of the precipitation differs in the northern and southern portions of the two river basins, changes are then preferably assessed in subregions. The model-dependent results project the following changes in the physical and dynamic mechanisms toward the end of the twenty-first century: (i) intensification of the 850-hPa northerly moisture flux from the western tropical Atlantic in the eastern side of the central Andes; and (ii) increase in the magnitude of the 200-hPa wind core whose location largely coincides with the La Plata basin. Those changes may increase the precipitation in the northern Amazon and southern La Plata basins by the end of the century. In contrast, the decrease in precipitation in the northern La Plata basin may result from the decrease in length of the rainy season associated with South American Monsoon System.

The focus of this work is on small municipalities (population below 50 thousand inhabitants) that cover around 87% of the territory of the Brazilian Legal Amazon (BLA). Based on a comprehensive integrated analysis approach using the three components hazard (climate extremes from CMIP6 future scenarios), exposure (directly affected population), and vulnerability (subdimensions of susceptibility and coping/adaptive capacity by using multidimensional indicators), the latter two using current datasets provided by the official Census IBGE 2022, we document a quantitative assessment of the risk R of natural disasters in the BLA region. We evidenced a worrying and imminent intensification of the curve of R in most Amazonian municipalities over the next two 25-year periods. The overall results of the highest proportions of R (total municipalities affected) pointed out the Amazonas, Roraima, Pará, and Maranhão as the main states, presenting projected categories of R high in the near future (2015 to 2039) and very high in the far future (2040 to 2064). The detailed assessment of the susceptibility and coping/adaptive capacity allowed us to elucidate the principal indicators that aggravate the degree of vulnerability: economy, the precariousness of urban infrastructure, medical services, communication, and urban mobility, whose combined factors, unfortunately, reveal a widespread poverty profile along the small Amazonian municipalities. Our scientific findings can assist decision makers in targeted strategies planning and public policies to minimize and mitigate ongoing and future climate change.

Background Carnivore mammals are animals vulnerable to human interference, such as climate change and deforestation. Their distribution and persistence are affected by such impacts, mainly in tropical regions such as the Amazon. Due to the importance of carnivores in the maintenance and functioning of the ecosystem, they are extremely important animals for conservation. We evaluated the impact of climate change on the geographic distribution of carnivores in the Amazon using Species Distribution Models (SDMs). Do we seek to answer the following questions: (1) What is the effect of climate change on the distribution of carnivores in the Amazon? (2) Will carnivore species lose or gain representation within the Protected Areas (PAs) of the Amazon in the future? Methods We evaluated the distribution area of 16 species of carnivores mammals in the Amazon, based on two future climate scenarios (RCP 4.5 and RCP 8.5) for the year 2070. For the construction of the SDMs we used bioclimatic and vegetation cover variables (land type). Based on these models, we calculated the area loss and climate suitability of the species, as well as the effectiveness of the protected areas inserted in the Amazon. We estimated the effectiveness of PAs on the individual persistence of carnivores in the future, for this, we used the SDMs to perform the gap analysis. Finally, we analyze the effectiveness of PAs in protecting taxonomic richness in future scenarios. Results The SDMs showed satisfactory predictive performance, with Jaccard values above 0.85 and AUC above 0.91 for all species. In the present and for the future climate scenarios, we observe a reduction of potencial distribution in both future scenarios (RCP4.5 and RCP8.5), where five species will be negatively affected by climate change in the RCP 4.5 future scenario and eight in the RCP 8.5 scenario. The remaining species stay stable in terms of total area. All species in the study showed a loss of climatic suitability. Some species lost almost all climatic suitability in the RCP 8.5 scenario. According to the GAP analysis, all species are protected within the PAs both in the current scenario and in both future climate scenarios. From the null models, we found that in all climate scenarios, the PAs are not efficient in protecting species richness.

The biosphere is undergoing critical transformations due to deforestation, agricultural expansion, and logging, which have led to biodiversity loss, degradation of ecosystem services, and climate change. In tropical forests such as the Ecuadorian Amazon, these pressures are especially severe because reductions in forest cover compromise key ecological processes. The purpose of this article is to analyze the relationship between shifting agriculture, food security, and conservation in the Ecuadorian Amazon, with emphasis on the agroforestry system known as the chakra practiced by Kichwa communities. This model integrates crops such as cacao, maize, and cassava with native trees, without chemical inputs, and constitutes a practice that is both culturally significant and environmentally sustainable. Whereas conventional shifting agriculture tends to reduce soil fertility and the forest’s regenerative capacity, chakras maintain important levels of floristic diversity, favor the conservation of endemic species, and provide ecosystem services such as carbon sequestration and nutrient regulation. In this sense, chakras represent a resilient yet context-dependent agroforestry alternative that connects food security and sovereignty, biological conservation, income, Indigenous identity, and climate-change mitigation, although their long-term sustainability remains influenced by market forces, land-use pressure, and policy support in tropical contexts.

Modelling continental freshwater dynamics is expected to be challenging in regions with considerable influence of multi-scale global climatic drivers. An assessment of the interplay between these climatic drivers (e.g. El-Niño Southern Oscillation-ENSO) that influence hydro-climatic conditions and hydrological processes is therefore required to optimize predictive frameworks. The main aim of this study is to assess the impacts of eleven key climate modes describing oceanic variability in the nearby oceans on the spatial and temporal distributions of terrestrial water storage (TWS) derived from Gravity Recovery and Climate Experiment (GRACE) (2002 − 2017) over South America (SA). Considering that SA accounts for nearly one-fifth of global continental freshwater discharge, this assessment is crucial because of the differences in the intrinsic response of freshwater availability in some regions to several important processes of inter-annual variability. The novel integration of independent component analysis with parameter estimation techniques in this study shows that climate variability drivers (ENSO; Southern Oscillation Index (SOI); Pacific Decadal Oscillation (PDO); Ninos 1 + 2, 3.0, 3.4 and 4.0; North Tropical Atlantic (NTA); and the Caribbean Sea Surface Temperature (SST) anomalies) have considerable association (α = 0.05) with GRACE-derived TWS over SA. The influence of Nino 4.0 (r = − 0.72), Nino 3.4 (− 0.68), Nino 3.0 (− 0.53), ENSO (r = − 0.71), PDO (r = − 0.69), SOI (r = 0.64), Caribbean SST (r = − 0.67) and NTA (r = − 0.51) on TWS are relatively stronger in tropical SA (Amazon basin/northern SA) and result in higher amplitudes of TWS (> 100 mm). Given the temporal and spatial relationships of TWS with PDO over SA, there is also evidence to suggest strong multi-decadal variability in TWS.