Combining Global Remote Sensing Products with Hydrological Modeling to Measure the Impact of Tropical Forest Loss on Water-Based Ecosystem Services

Abstract

In the Lower Mekong River Basin (LMB), deforestation rates are some of the highest in the world as land is converted primarily into intensive agriculture and plantations. While this has been a key for the region’s economic development, rural populations dependent on the freshwater water resources that support their fishing and agriculture industries are increasingly vulnerable to the impacts of flood, drought and non-point source pollution. Impacts of deforestation on ecosystem services (ES) including hydrological ES that control the availability and quality of fresh water across the landscape, regulating floods and droughts, soil erosion and non-point source pollution are known. Despite this understanding at the hillslope level, few studies have been able to quantify the impact of wide-scale deforestation on larger tropical watersheds. This study introduces a new methodology to quantify the impact of deforestation on water-based ES in the LMB with a focus on Cambodia by combining spatial datasets on forest loss from remote sensing and spatially-explicit hydrological modeling. Numerous global and regional remote sensing products are synthesized to develop detailed land use change maps for 2001 to 2013 for the LMB, which are then used as inputs into a hydrological model to develop unique spatial datasets that map ES changes due to deforestation across the LMB. The results point to a clear correlation between forest loss and surface runoff, with a weaker but upward trending relationship between forest loss and sediment yield. This resulted in increased river discharge for 17 of the 22 watersheds, and increased sediment for all 22 watersheds. While there is considerable variability between watersheds, these results could be helpful for prioritizing interventions to decrease deforestation by highlighting which areas have experienced the greatest change in water-based ES provision. These results are also presented in a web-based platform called the Watershed Ecosystem Service Tool.

Response of Ecosystem Water Use Efficiency to Drought over China during 1982–2015: Spatiotemporal Variability and Resilience

“…Especially, high resolution drought monitoring datasets would undoubtedly be helpful to improve the robustness of related studies. Nevertheless, our findings revealed that the non-resilient ecosystems would encounter more challenges in ecological protection, agricultural production and carbon sequestration in the future due to increasing drought disturbances [29,72]. Policy makers could make reasonable water use strategies and efficient ecosystem management pathways to minimize the effects of drought under the warming climate.…”

Mapping Land Use Land Cover Change in the Lower Mekong Basin From 1997 to 2010

“…Also, our study area only partially covers Cambodia. Netzer et al (2019) noted that considerable deforestation occurs is in the Tonle Sap sub-basin of Cambodia, which is outside the study area for our LULC change map.…”

“…For example, evergreen broadleaved forests have a lower runoff potential (i.e., SCS curve number) than agricultural cropland for given hydrologic soil group and hydrologic condition class (Hong and Adler, 2008). Extensive conversion of forests to permanent crops or other non-forests can change the runoff characteristics within a subbasin (Netzer et al, 2019). Consequently, forests are a preferred LULC type by the MRC for catchments being used for water supplies (MRC, 2010).…”

Managing Forests and Water for People under a Changing Environment

“…The Forest-Water Network: Planning tools This book represents a collection of some of the peer-reviewed papers presented at the Conference that are published in a special issue in Forests (https://www.mdpi.com/journal/forests/special_issues/ Forests_Water). These studies cover a large physiographic gradient across major continents and climatic zones including the temperate rainforests in Chile [1][2][3] and the subtropical forests in Brazil [4] and South America; temperate rainforests [5] and boreal forests [6] in North America; and the large tropical Mekong River Basin in Vietnam [7], the Nenjian River in the boreal northeastern China [8], and the arid Loess Plateau in northern China [9], in east Asia. Five papers addressed issues of the effects of water quantity and quality of native forest buffers on dissolved organic matter in forested and agricultural watersheds in northwestern Patagonia [1]; effects of eucalyptus management on nutrient and sediments in small watersheds in Brazil [4]; effects of pine and eucalyptus plantation forests on water supply for large watersheds (>200 km 2 ) in south central Chile [3]; effects of forests and wetlands on water yield, surface runoff and baseflow in northeastern China [8], and the combined effects of climate and afforestation on soil moisture in Loess Plateau of China [9].…”

“…Five papers addressed issues of the effects of water quantity and quality of native forest buffers on dissolved organic matter in forested and agricultural watersheds in northwestern Patagonia [1]; effects of eucalyptus management on nutrient and sediments in small watersheds in Brazil [4]; effects of pine and eucalyptus plantation forests on water supply for large watersheds (>200 km 2 ) in south central Chile [3]; effects of forests and wetlands on water yield, surface runoff and baseflow in northeastern China [8], and the combined effects of climate and afforestation on soil moisture in Loess Plateau of China [9]. Five papers addressed management issues: Managing headwater streams under climate change [5]; local communities' participation in watershed management [2]; the nexus of forests, water, and policy [10]; ecosystem services in the Mekong River Basin [7] and; risk assessment of wildland fires in Alberta, Canada [6]. In summary, worldwide studies clearly show that forests and water are intimately connected, and forest management policies must balance the tradeoffs of ecosystem services and adapt to global environmental changes in order to meet sustainable development goals.…”