A regional view of the linkages between hydro‐climatic changes and deforestation in the Southern Amazon

Abstract

In the last four decades, the Southern Amazon (south of 8 S) has shown changes in the spatial and temporal patterns of its hydro-climatic components, leading to drier conditions. Due to climate and land-use changes, this region is considered as a zone under biophysical transition processes. Previous studies have documented a complex interaction between climate and deforestation either on a large-scale or based on limited in situ data, typically covering the Brazilian Amazon. In this study, we analyse the relationships between hydro-climate, the surface waterenergy partitioning and an index of regional forest cover change for the period 1981-2018. Additionally, we discretized three regions covering the Bolivian Amazon and the southern portions of the Peruvian and Brazilian Amazon due to their differences in the evolution of land use. In the Bolivian region, a high ratio of forest cover change, exceeding 40-50%, is related to a significant tendency to become water-limited. This change is associated with decreased rainfall, increased potential evapotranspiration and decreased actual evapotranspiration. Regardless of the region analysed, those that are characterized by a high ratio of forest cover change (>40-50%) show growing imbalance between increasing potential and decreasing actual evapotranspiration. However, in the Peruvian and Brazilian regions, hydroclimatic conditions remain energy-limited due to minor rainfall changes. The observed differences in surface water-energy partitioning behaviour evidence a complex dependence of both sub-regional (i.e., land cover changes) and large-scale (i.e., strengthening of the Walker and Hadley circulations) conditions. Our findings indicate a clear link between hydro-climatic changes and deforestation, providing a new perspective on their spatial variability on a sub-regional scale.

Circulation Patterns and Associated Rainfall Over South Tropical South America: GCMs Evaluation During the Dry‐To‐Wet Transition Season

“…Emerging recognition has been seen on the effects of climate change in STSA as ongoing changes in its hydro‐climatic regimes and weather patterns have been identified, including a lengthening of the dry season associated with a delayed onset of the SAMS (e.g., Arias et al., 2015; Caballero et al., 2022; Correa et al., 2021; Debortoli et al., 2015; Espinoza et al., 2021; Fu et al., 2013; Jones & Carvalho, 2002; Marengo et al., 2012; Pascale et al., 2019; Wongchuig et al., 2021). Moreover, deforestation and climate change are altering the Amazon rainforest, promoting an ecosystem stress favoring biomass loss, tree mortality and fire activity (Gatti et al., 2021; Reis et al., 2018; Silva et al., 2020).…”

“…During the recent decades, STSA has experienced an increase in dry conditions over southern Amazonia – around 5°–15°S and 70°–50°W – during the dry‐to‐wet transition season (approximately from July to October) and a lengthening of the dry season associated with a delayed SAMS onset (Arias et al., 2015; Correa et al., 2021; Debortoli et al., 2015; Espinoza et al., 2019; Fu et al., 2013; Giráldez et al., 2020; Pascale et al., 2019). The most recent climate report of the Intergovernmental Panel on Climate Change (IPCC) indicates high confidence on a delayed onset of the SAMS, which is influenced by anthropogenic forcings such as land‐use and deforestation changes, that induce modifications in the STSA hydrological cycle and atmospheric circulation (Alves et al., 2017; Caballero et al., 2022; Costa & Pires, 2010; Marengo et al., 2018; Ruiz‐Vasquez et al., 2020; Sierra et al., 2021; Silva et al., 2020; Wongchuig et al., 2021; Zilli & Carvalho, 2021). All of these topics are currently central issues within the scientific community since the modification of the surface‐atmosphere feedbacks endangers biodiversity and human activities (Bombardi et al., 2019; Gatti et al., 2021; Staal et al., 2018).…”

Spatiotemporal Variations of Evapotranspiration in Amazonia Using the Wavelet Phase Difference Analysis

“…Vegetation in the southern Amazon is particularly sensitive to changes in the length of the dry season. It is widely affected by anthropogenic forcing, especially along the “Arc of Deforestation” around the southeast edge of the forest (Wongchuig et al., 2021). Therefore, $${\phi }_{ET-LAI}^{1-degree}$$ in the southern Amazon are complex, which may be caused by the anthropogenic activities in areas like pasture, agriculture, and deforested area.…”

The South American monsoon approaches a critical transition in response to deforestation

“…Widespread deforestation and drought-or fire-induced forest dieback, via their effects on transpiration rates and radiation, have been shown to potentially trigger a collapse of the positive feedback related to convective latent heating, resulting in abrupt reductions in rainfall amounts after a critical deforestation threshold around 40% is crossed (5,21,23). This effect can already be observed in regions with high forest cover changes of 40 to 50%, with a growing tendency to become water limited due to decreased rainfall, increased potential evapotranspiration, and decreased actual evapotranspiration (49).…”