Modeling the "biotic pump": quantifying the role of ecosystem transpiration in water cycle and temperature mitigation

The terrestrial water cycle links the soil and atmosphere moisture reservoirs through four fluxes:
precipitation, evaporation, runoff, and atmospheric moisture convergence (net import of water vapor
to balance runoff). Each of these processes is essential for sustaining human and ecosystem
well-being. Predicting how the water cycle responds to changes in vegetation cover remains a
challenge. Recently, changes in plant transpiration across the Amazon basin were shown to be
associated disproportionately with changes in rainfall, suggesting that even small declines in
transpiration (e.g., from deforestation) would lead to much larger declines in rainfall. Here,
constraining these findings by the law of mass conservation, we show that in a sufficiently wet
atmosphere, forest transpiration can control atmospheric moisture convergence such that increased
transpiration enhances atmospheric moisture import and results in water yield. Conversely, in a
sufficiently dry atmosphere increased transpiration reduces atmospheric moisture convergence and
water yield. Modeling the potential of vegetation for enhancing moisture convergence is crucial for
characterizing the consequences of deforestation as well as for motivating and guiding ecological
restoration.

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Referente: Davide Quaglia