Land-Cover Changes effects on Water-Carbon fluxes in a Colombian Amazonian basin

Extractivism driven by licit and illicit economic activities has generated negative effects on natural land-covers and biodiversity, increasing ecosystem vulnerability as a consequence of local hydroclimatic fluxes alterations, as well as those transcending geographic boundaries. One of the main current drivers is deforestation, which in tropical regions has altered ecosystem carbon storage capacity, however, it's relationship with local hydroclimatic alterations has been poorly addressed. This study evaluates the relationship between land-cover changes and hydroclimatic dynamics through the analysis of actual [AET] and potential [PET] evapotranspiration, precipitation [P], and runoff [R], as well as their implications for terrestrial carbon uptake in the Upper Putumayo river basin, located in Colombia within the Amazon region and in an ecosystem convergence zone with the Andean region.  The analysis covers the 2000–2022 period and is based on remote sensing tools and in situ data under the Budyko framework, assessing water deficit in relation to biomass production in remaining forest ecosystems. Results show that deforested areas exhibit increased runoff, associated with reduced vegetation interception and greater exposure of bare soils, leading into diminished hydrological regulation capacity. Additionally, the basin maintains low evaporative ratios (AET/P = 0.346) despite a decrease in the aridity index (ΔPET/P = −0.023), evidencing an ecohydrological decoupling, which can be attributed to vegetation control loss. These changes reflect an increase in effective water deficit and coincide with reduced primary productivity [GPP and NPP], suggesting forest's lower capacity for terrestrial carbon sequestration.