This paper synthesizes the spatial and temporal relationship between forest cover and water, as well as its implications for food security in the northwestern highlands of Ethiopia. Different studies addressing the topic of land cover and hydrology have been reviewed. Analyses of 20–40 year long time series showed little and inconsistent relationships between forest cover change and hydrology on meso-scale (100–1000km2) watersheds. Spatial studies, however, showed stronger relationships between land cover and low flow features such as grasslands and woodlands. Interviews with local communities suggested land cover change impacts are more pronounced at smaller scale (<100km2) watersheds; which is consistent with observational studies on small scale watersheds and farm level plots. The stronger relationships between forests and hydrology at smaller scales suggests land management policies should be oriented to farm level conditions, where water is vital for the food security of subsistence farmers who comprise 86% of the population in the highlands.

The food-water-energy nexus concept helps to produce an integrative solutions to secure the water-related ecosystem services sustainably. This study aims to quantify and map water provisioning and soil erosion regulating services from both demand and supply sides in a spatially explicit manner. It considers the Wabe River catchment of the Omo-Gibe Basin in tropical data-sparse region of East Africa as a case study and uses the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) annual and seasonal water yield and sediment delivery models. The water demands and biophysical parameters data were collected from primary and secondary sources and prepared according to the requirement of the models. The models output were validated after conducting sensitivity analysis of the input parameters. The result shows that the rainfall amount of the catchment is highly seasonal, which causes the surface water to vary according to the seasons. The high annual precipitation and low actual evapotranspiration of the catchment resulted high annual water yields. However, the people in the catchment did not satisfied their domestic water demand as result of inaccessibility and poor management of the rain water. The high net supply of water, especially in the rainy season, carries detached top soil via heavy rainfall in the upper catchment areas. Even though the existing land cover and management practices contribute to sediment retention, a large amount of sediment is exported to rivers, which jeopardizes the food and energy security. Thus, the management of water is essential for enhancing the security of the food-water-energy nexus in the catchment. The methods applied in this study can increase spatial understanding of the water-related ecosystem services especially in data–sparse catchments of the tropics, and lead to improvement of water management to enhance the security nexus.

Changes in watershed land cover have an impact on reducing water discharge, as well as other derivative impacts such as the productivity of food crops, horticulture, and plantations. This study tries to offer a conceptual model of the effect of changes in watershed land cover, water discharge, and food productivity through food crops, horticultural crops, and plantation crops. This study uses a quantitative approach based on time series data between 2002 and 2021. Data is analyzed using a structural model approach with SEM-SmartPLS software. As a result, changes in land cover have a significant effect on water discharge, but they have no effect on food productivity. Water discharge has a significant effect on food production, and changes in land cover greatly affect food productivity through the role of intermediary variables (mediation) of water discharge. In 2041, changes in land cover can reduce water discharge by around 47.9%. Then the water discharge is estimated to have an impact on the productivity of food crops by 62.3%, vegetable productivity by around 45.7%, and plantation crop productivity by around 72.7%.

Lotic systems in many regions of the country have experienced habitat degradation and biodiversity loss due to agricultural activity and urbanization. Southeastern Michigan is no exception, as agriculture in the River Raisin watershed and increased urbanization in the Huron River watershed threatens both systems. To further understand the ecological impact of land use on trophic interactions in Midwestern streams and assess the use of a selected set of weighted, quantitative food web metrics as a tool for investigating the influence of anthropogenic disturbance on these systems we compared summer food webs for nine second-order streams. All streams were categorized as developed, undeveloped, or agricultural based on land cover data. Developed and undeveloped streams were located in the Huron River watershed and agricultural streams were located in the River Raisin watershed. Reach-level habitat quality was also assessed at each study site using the EPA's Rapid Habitat Assessment. Fish diets (n = 410) were analyzed to create summer food webs for each site. Comparisons of food webs were made using a suite of weighted, quantitative metrics to identify differences in fish-macroinvertebrate interactions across streams with differing land cover at the sub-basin scale and habitat quality at the local scale. Although undeveloped streams had higher species richness and less habitat degradation, no significant patterns were observed in the quantitative metrics across the three stream categories or based on reach-level habitat conditions. Decapoda, terrestrial Hymenoptera, and Chironomidae were the primary prey taxa in all stream categories. Decapods accounted for the majority of biomass consumed and the pattern of this consumption strongly influenced metric scores. The suite of quantitative metrics tested in this study did not detect significant differences in fish-macroinvertebrate food webs across land use categories, likely in part due to the dominance of a large, tolerant prey taxa in fish diets, regardless of land use and local habitat quality.

Of all the challenges facing the sustainability of cities, water, food and energy are the most critical. In the context of rapid urbanization, unsustainable human activities have resulted in fundamental changes in the structure and function of land cover and urban water systems, and the degradation of ecosystem services. Taking Beijing - a typical fast-growing mega city - as an example, to establish a food-energy-water impact model, this research studied the temporal-spatial changes in the water system pattern in a mega city, along with the driving forces, especially the nexus to rice production and energy, and the ensuing series of environmental impacts.On the basis of land use data, remote sensing images, and thematic maps from 1993, 2001 and 2007, water system information was extracted and adjusted for Beijing. With the aid of RS and GIS techniques, the water system was classified into four types, and the spatial and temporal dynamic of the landscape patterns of Beijing’s water system systematically was analyzed. The landscape metrics were then calculated using FRAGSTATS 3.3. The results show that the total area of water system in Beijing declined from 63,494 ha to 43,652 ha from 1993 to 2007. The decrease of the linear water surface is more significant than that of the non-linear water surface. In the terms of landscape metrics change, the number of patches has decreased from 5510 to 5396. The density indexes have increased by 40.61%, the average area of patches has decreased by 30.18%, the patch shape has tended to become more regular, and the overall pattern of the water system is becoming more fragmented. Urban sprawl, the shortage of water resources, and the increasing amount of construction land are the major reasons accounting for the changes in the water system in Beijing. Because of these changes, farmland has decreased by 212,428 ha, and especially rice paddy fields, are significantly decreasing from 52,200 ha in 1980 to 199.6 ha in 2015, a decrease of 99.62%. Consequently, rice production is decreasing by 99.61%, more energy is being consumed for food production. Meanwhile, the local water supply rate has decreased from 100% to 78.4% between 2001 to 2016, the underground water level has decreased by 14.24 m from 1994 to 2016. There is more competition for water resources, more urban water flooding disasters, and emerging urban environmental problems such as declining underground water level, posing a serious threat to the sustainability of the city. Therefore, a systematic and smart thinking is needed to analyze the complex land use - water- food – energy relationship.

The objective of this study was to investigate the changes in cropland areas as a result of water availability using Moderate Resolution Imaging Spectroradiometer (MODIS) 250 m time-series data and spectral matching techniques (SMTs). The study was conducted in the Krishna River basin in India, a very large river basin with an area of 265 752 km2 (26 575 200 ha), comparing a water-surplus year (2000-2001) and a water-deficit year (2002-2003). The MODIS 250 m time-series data and SMTs were found ideal for agricultural cropland change detection over large areas and provided fuzzy classification accuracies of 61-100% for various land-use classes and 61-81% for the rain-fed and irrigated classes. The most mixing change occurred between rain-fed cropland areas and informally irrigated (e.g. groundwater and small reservoir) areas. Hence separation of these two classes was the most difficult. The MODIS 250 m-derived irrigated cropland areas for the districts were highly correlated with the Indian Bureau of Statistics data, with R2-values between 0.82 and 0.86. The change in the net area irrigated was modest, with an irrigated area of 8 669 881 ha during the water-surplus year, as compared with 7 718 900 ha during the water-deficit year. However, this is quite misleading as most of the major changes occurred in cropping intensity, such as changing from higher intensity to lower intensity (e.g. from double crop to single crop). The changes in cropping intensity of the agricultural cropland areas that took place in the water-deficit year (2002-2003) when compared with the water-surplus year (2000-2001) in the Krishna basin were: (a) 1 078 564 ha changed from double crop to single crop, (b) 1 461 177 ha changed from continuous crop to single crop, (c) 704 172 ha changed from irrigated single crop to fallow and (d) 1 314 522 ha changed from minor irrigation (e.g. tanks, small reservoirs) to rain-fed. These are highly significant changes that will have strong impact on food security. Such changes may be expected all over the world in a changing climate.

The objective of this study was to investigate the changes in cropland areas as a result of water availability using Moderate Resolution Imaging Spectroradiometer (MODIS) 250 m time-series data and spectral matching techniques (SMTs). The study was conducted in the Krishna River basin in India, a very large river basin with an area of 265 752 km2 (26 575 200 ha), comparing a water-surplus year (2000-2001) and a water-deficit year (2002-2003). The MODIS 250 m time-series data and SMTs were found ideal for agricultural cropland change detection over large areas and provided fuzzy classification accuracies of 61-100% for various land-use classes and 61-81% for the rain-fed and irrigated classes. The most mixing change occurred between rain-fed cropland areas and informally irrigated (e.g. groundwater and small reservoir) areas. Hence separation of these two classes was the most difficult. The MODIS 250 m-derived irrigated cropland areas for the districts were highly correlated with the Indian Bureau of Statistics data, with R2-values between 0.82 and 0.86. The change in the net area irrigated was modest, with an irrigated area of 8 669 881 ha during the water-surplus year, as compared with 7 718 900 ha during the water-deficit year. However, this is quite misleading as most of the major changes occurred in cropping intensity, such as changing from higher intensity to lower intensity (e.g. from double crop to single crop). The changes in cropping intensity of the agricultural cropland areas that took place in the water-deficit year (2002-2003) when compared with the water-surplus year (2000-2001) in the Krishna basin were: (a) 1 078 564 ha changed from double crop to single crop, (b) 1 461 177 ha changed from continuous crop to single crop, (c) 704 172 ha changed from irrigated single crop to fallow and (d) 1 314 522 ha changed from minor irrigation (e.g. tanks, small reservoirs) to rain-fed. These are highly significant changes that will have strong impact on food security. Such changes may be expected all over the world in a changing climate.