Can forests improve hydrological ecosystem services?
Doctoral candidate Daniela Ávila-García and Dr. Jordi Morató conducted a study to analyze the relationship between forest cover and water (quality and supply) in a basin of ecological, tourist and cultural importance in Mexico.
Barcelona, October 1
Hydrological ecosystem services (HES) are related to aquatic ecosystems and their transition zones with other terrestrial ecosystems. In particular, several studies have shown that the presence of forests has a positive effect on hydrological functioning. However, changes in land use have modified the capacity of forests to provide SEH globally. The Rio Grande de Comitán-Lagos de Montebello basin (RGC-LM) is located in the south-southeast region of the State of Chiapas, Mexico. In recent decades, changes in land use, deforestation, and accelerated agricultural, urban and tourist growth have caused problems of water scarcity, contamination in the WCR and eutrophication in some of the lakes that are part of the National Park "Lagunas de Montebello".
In basis of the study, we recently analyze the relationship between forests and SEH based on a combination of methods recommended by TESSA (Toolkit for Ecosystem Service Site-based Assessment), which included interviews in eleven localities (ejidos), as well as the modeling of land use change scenarios using WaterWorld, statistical analysis, and the application of an ecological quality index (RQI-Riparian Quality Index). The objective was to identify the spatial distribution of two SEH (water quality and supply) and their main beneficiaries in order to subsequently analyze the potential impacts of four scenarios of land use change at the basin and sub-basin scale.
Two scenarios were focused on mitigating the possible consequences derived from agricultural growth and deforestation: 1) BS20- vegetation strips (20 m along the river network) were simulated in conjunction with reforestation strategies (20% of each pixel at the scale of 1-ha); 2) R15- reforestation (15%). In contrast, the other two scenarios represented an increase in deforestation and degradation of riparian vegetation: 1) D15- deforestation (15%); 2) D20- degradation of vegetation strips (20 m) plus deforestation (20%).
The results demonstrated a positive relationship between forest cover and water quality. At the basin level, the amount of available water also increased the average values in the reforestation scenarios, while the deforestation scenarios projected the opposite. However, some specific areas decreased the amount of water in the reforestation scenarios. This suggests that local water demands, including evapotranspiration and the amount of fog intercepted by forests, should be considered in future restoration plans, especially in ejidos that lack efficient water distribution networks. This study provides an overview of the management of water resources in the RGC-LM basin and contributes to the analysis of the possible hydrological impacts as a consequence of changes in land use at different scales. This approach also made it possible to identify sub-basins where the conservation or restoration of forest ecosystems and mountain areas could be a priority to maintain or improve the provision of SEH in the study area.
Download the original article:
Ávila-García, D., Morató J., Pérez A., Santillán-Carvantes, P., Alvarado, J., Comín, F. 2020. Impacts of alternative land-use policies on water ecosystem services in the Río Grande de Comitán-Lagos de Montebello watershed, México. Ecosystem Services. 45. https://doi.org/10.1016/j.ecoser.2020.101179