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Soil conservation measures including cutoff drains, tree planting, Crops diversifications and destocking were implemented in Kondoa eroded area (KEA) for decades. This study assessed soil erosion changes in KEA and examined drivers of changes using Universal Soil Loss Equation, Geographic Information Systems and socioeconomic survey. Soil erosion was predicted by using data on soil, digital elevation model, rainfall and land use/cover visually interpreted from multitemporal satellite imageries. The predicted average soil erosions were 14Á7, 23 and 15.7 Mg ha À1 y À1 during 1973, 1986 and 2008, respectively. The area under very high soil erosion severity that was 30% in 1973, 26% in 1986 and 25% in 2008, whereas the area with high erosion severity was 26% in 1973 changed into 49% in 1986 and 2008 indicating recent stabilization. The area with moderate erosion increased from 15%, 16% and 18% during the same period. Field survey confirms a decrease of soil erosion in KEA compared with the past showing better soil conservation. Age of farmers, long-term adoption of conservation practices and on-farm tree planting were found to be the major factors contributing toward reduced soil erosion. Major limitations in soil conservation were poor mainstreaming of conservation activities on local production systems and lack of institutions promoting conservation at the community level. The study concluded that long-term conservation investment for restoration, protection and socioeconomic support contributes significantly in land rehabilitation in KEA.

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As more data and technologies become available, it is important that a simple method is developed for the assessment of land use changes because of the global need to understand the potential climate mitigation that could result from a reduction in deforestation and forest degradation in the tropics. Here, we determined the threshold values of vegetation types to classify land use categories in Cambodia through the analysis of phenological behaviors and the development of a robust phenology-based threshold classification (PBTC) method for the mapping and long-term monitoring of land cover changes. We accessed 2199 Landsat collections using Google Earth Engine (GEE) and applied the Enhanced Vegetation Index (EVI) and harmonic regression methods to identify phenological behaviors of land cover categories during the leaf-shedding phenology (LSP) and leaf-flushing phenology (LFS) seasons. We then generated 722 mean phenology EVI profiles for 12 major land cover categories and determined the threshold values for selected land cover categories in the mid-LSP season. The PBTC pixel-based classified map was validated using very high-resolution (VHR) imagery. We obtained a cumulative overall accuracy of more than 88% and a cumulative overall accuracy of the referenced forest cover of almost 85%. These high accuracy values suggest that the very first PBTC map can be useful for estimating the activity data, which are critically needed to assess land use changes and related carbon emissions under the Reducing Emissions from Deforestation and forest Degradation (REDD+) scheme. We found that GEE cloud-computing is an appropriate tool to use to access remote sensing big data at scale and at no cost.

Ecosystem services are highly vulnerable to a number of impacts due to the complex effects of human use of natural resources and subsequent land use change. Assessment of the impact of change in land use with respect to ecosystem services is necessary in order to implement appropriate land uses that enhance ecosystem services. This study analysed the impact of change in land use on ecosystem services using the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model to map and quantify a set of ecosystem services, namely sediment retention, water yield, carbon stock, and habitat quality, in northern Thailand, which has experienced substantial policy induced land use change. The study also assessed the changes in land use from 1989 to 2013 and their impact on overall ecosystem services using GIS. Increased rubber plantation cultivation and built-up areas resulting in reduced forest cover were the major changes found in land use in the area. The results of the study show a general decrease in ecosystem services for the study period in the watershed, in particular, a negative impact on ecosystem services was observed in agricultural areas. The study findings on spatial and temporal distribution of ecosystem services can help guide the development of appropriate land use options to enhance ecosystem services.