Deforestation Impacts on Amazon-Andes Hydroclimatic Connectivity

Abstract

Amazonian deforestation has accelerated during the last decade, threatening an ecosystem where almost one third of the regional rainfall is transpired by the local rainforest. Due to the precipitation recycling, the southwestern Amazon, including the Amazon-Andes transition region, is particularly sensitive to forest loss. This study evaluates the impacts of Amazonian deforestation in the hydro-climatic connectivity between the Amazon and the eastern tropical Andes during the austral summer (December-January-February) in terms of hydrological and energetic balances. Using 10-year high-resolution simulations (2001–2011) with the Weather Research and Forecasting Model, we analyze control and deforestation scenario simulations. Regionally, deforestation leads to a reduction in the surface net radiation, evaporation, moisture convergence and precipitation (~ 20%) over the entire Amazon basin. In addition, during this season, deforestation increases the atmospheric subsidence over the southern Amazon and weakens the regional Hadley cell. Atmospheric stability increases over the western Amazon and the tropical Andes inhibiting convection in these areas. Consequently, major deforestation impacts are observed over the hydro-climate of the Amazon-Andes transition region. At local scale, nighttime precipitation decreases in Bolivian valleys (~ 20–30%) due to a strong reduction in the humidity transport from the Amazon plains toward Andes linked to the South American low-level jet. Over these valleys, a weakening of the daytime upslope winds is caused by local deforestation, which reduces the turbulent fluxes at lowlands. These alterations in rainfall and atmospheric circulation could impact the rich Andean ecosystems and its tropical glaciers.

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

“…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).…”

“…STSA hosts the Amazonia ‐ the world's largest rainforest and one of the major sources of evapotranspiration ‐ playing a critical role in the global balances of energy, water, moisture and carbon (Gatti et al., 2021; Llopart et al., 2020). The region presents unique biodiversity and geographical patterns, mainly due to the interaction of the Amazonia and the Andes mountain range, which have deep implications in the atmospheric dynamics, moisture transport and river discharge not only throughout STSA but also in remote regions of the continent (Arias, Garreaud, et al., 2021; Espinoza et al., 2020; Sierra et al., 2021).…”

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

“…In the Southern Amazon, convective processes are particularly active (Vera et al ., 2006); therefore, a decrease in vertical wind could indicate a decrease in convective activity and rainfall. To gain a complete understanding of what is at play when relating the evolution of forest cover with rainfall changes, local processes should therefore be accounted for, through the use of tools such as numerical models (Eiras‐Barca et al ., 2020; Ruiz‐Vásquez et al ., 2020; Sierra et al ., 2021). For instance, in a recent high‐resolution modelling work, Sierra et al .…”

“…For instance, in a recent high‐resolution modelling work, Sierra et al . (2021) found that a deforestation scenario of 45% of the Amazonian forest produce decrease in evapotranspiration and vertically integrated moisture convergence in central and southern Amazon, which also implies a reduction in the vertical velocity. These regional changes due to Amazon deforestation are associated with a rise in the atmospheric pressure at lower levels.…”

“…These regional changes due to Amazon deforestation are associated with a rise in the atmospheric pressure at lower levels. This result suggests a complex interaction between changes in large‐scale atmospheric circulation (e.g., Walker and Hadley circulations) and regional changes due to forest loss (Sierra et al ., 2021).…”