Hydrological impacts of afforestation in the semiarid Patagonia: A modelling approach

Abstract

Afforestation has been widely encouraged with different goals, including as a strategy to tackle global warming. However, the side-effects of this land-use transformation have been in many cases underestimated. Particularly, the hydrological impacts may become relevant in (semi)arid regions where water is a key element. In this work, we evaluated the hydrological effects triggered by afforestation with ponderosa pine in the semiarid Argentine Patagonia that is currently a focus of afforestation programs. For this purpose, we used complementary approaches that included hydrological modelling (DINAQUA model), satellite image analysis, and soil wetness data. All analyses provided convergent results into hydrological effects of afforestation. The modelling results showed that afforestation significantly increased transpiration in relation to native grass-shrub steppe. In the steppe in degraded condition, transpiration accounted for only 10% (40 mm year −1 ) of total water flux, whereas in adult pine plantations, it accounted for up to 73% (277 mm year −1 ). Deep drainage was also severely affected by afforestation as it decreased from 182 mm year −1 in the steppe to zero in adult plantations, according to model simulations. Estimates from Landsat images also showed that evapotranspiration was higher in plantations compared with the steppe. Soil wetness data also revealed significantly drier soils in plantations. Our results indicate that pine plantations in the semiarid Patagonia evaporate all rainfall inputs, resulting in zero deep drainage and groundwater recharge. If the afforested area in the region increases, downstream meadow ecosystems, which are hotspots of primary productivity, may be negatively impacted.

Contrasting CO2 and water vapour fluxes in dry forest and pasture sites of central Argentina

“…For instance, interception rates of up to four times higher have been measured in dry forests of the region compared with pastures (Magliano et al, 2016). Likewise, the deeper root system would have allowed the dry forest to sustain higher ET rates than the pasture during drought, pattern already observed in grassland areas that were afforested (Milkovic et al, 2019; Nosetto, Jobbágy, Brizuela, & Jackson, 2012).…”

“…The NDVI and EVI are suitable indexes to assess the condition of the ecosystem, given their connection with primary productivity and green biomass (e.g., Goward & Dye, 1987; Sims et al, 2006). Likewise, Ts is closely associated with the heat exchange of vegetation canopies with the surrounding atmosphere and particularly with evapotranspiration (e.g., Milkovic, Paruelo, & Nosetto, 2019; Rotenberg & Yakir, 2010). For NDVI and EVI, we used the MOD13Q1 product and for Ts we used the MYD11A2 product.…”

Afforestation of Degraded Croplands as a Water-Saving Option in Irrigated Region of the Aral Sea Basin

“…Forests and trees are important modulators of global, regional, and local hydrological cycles and patterns [22,59,60]. Negative hydrological impacts, such as the depletion of soil water and reduced annual runoff and water yields, are often observed for dryland afforestation [18,20,24], especially in large-scale planting schemes [19,61]. However, with the excessive cropland irrigation in Khorezm [5]), the reduction in all examined water balance components following the afforestation of marginal land reflects the reduced irrigation inputs and lowered drainage output.…”

Climate and Land Cover Trends Affecting Freshwater Inputs to a Fjord in Northwestern Patagonia

“…Although these results may discourage conservation, Galleguillos et al (2021) reported that conservative scenarios focused on native forest protection and restoration could partially mitigate the effect of climate change in Mediterranean basins. Future efforts should focus on understanding the hydrological role of different vegetation cover (e.g., Milkovic et al, 2019), under changing climatic conditions in northwestern Patagonia.…”