Reducing food losses and waste is considered to be one of the most promising measures to improve food security in the coming decades. Food losses also affect our use of resources, such as freshwater, cropland, and fertilisers. In this paper we estimate the global food supply losses due to lost and wasted food crops, and the resources used to produce them. We also quantify the potential food supply and resource savings that could be made by reducing food losses and waste. We used publically available global databases to conduct the study at the country level. We found that around one quarter of the produced food supply (614 kcal/cap/day) is lost within the food supply chain (FSC). The production of these lost and wasted food crops accounts for 24% of total freshwater resources used in food crop production (27 m3/cap/yr), 23% of total global cropland area (31 × 10− 3 ha/cap/yr), and 23% of total global fertiliser use (4.3 kg/cap/yr). The per capita use of resources for food losses is largest in North Africa & West-Central Asia (freshwater and cropland) and North America & Oceania (fertilisers). The smallest per capita use of resources for food losses is found in Sub-Saharan Africa (freshwater and fertilisers) and in Industrialised Asia (cropland). Relative to total food production, the smallest food supply and resource losses occur in South & Southeast Asia. If the lowest loss and waste percentages achieved in any region in each step of the FSC could be reached globally, food supply losses could be halved. By doing this, there would be enough food for approximately one billion extra people. Reducing the food losses and waste would thus be an important step towards increased food security, and would also increase the efficiency of resource use in food production.
For the purpose of global modeling of water use and crop production, a digital global map of irrigated areas was developed. The map depicts the percentage of each 0.5° by 0.5° cell that was equipped for irrigation in 1995. It was derived by combining information from large-scale maps with outlines of irrigated areas (one or more countries per map), FAO data on total irrigated area per country in 1995 and national data on total irrigated area per county, drainage basin or federal state. This documentation describes the dataset, the data and map sources as well as the map generation, and it discusses the data uncertainty. We plan to improve this map in the future. Therefore, comments, information and data that might contribute to this effort are highly welcome. Doell and Siebert A Digital Global Map of Irrigated Areas
Crop water requirements of irrigated crops and crop water use of rainfed crops is calculated by the Global Crop Water Model (GCWM) for the period 1998-2002 based on a soil water balance performed in daily time steps.Crop yields of rainfed and irrigated crops are distinguished by downscaling yields reported in national and subnational agricultural statistics (Monfreda et al., 2008) by considering drought stress simulated for rainfed agriculture. Virtual water contents are calculated as ratio between crop water use and crop yield. Domestic virtual water flows are determined by calculating a balance between crop production and crop consumption at grid cell level and establishing flows from surplus cells (major production areas) to deficit cells (highly populated regions). Crop growing areas, sowing and harvest dates were derived from the global data set of monthly irrigated and rainfed crop areas around the year 2000 (MIRCA2000). Consequently, crop water use (blue and green) is computed for the crops wheat, rice, maize, barley, rye, millet, sorghum, soybeans, sunflower, potatoes, cassava, sugar cane, sugar beet, oil palm, rapeseed/canola, groundnuts/peanuts, pulses, citrus, date palm, grapes/vine, cocoa, coffee, cotton and unspecified other crops (other perennial crops, other annual crops, fodder grasses). For the calculation of crop yields, virtual water contents and virtual water flows we distinguish in addition the usage of maize, rye and sorghum for grain or forage. Virtual water flows are computed for crops traded mainly as primary commodities (all specific crops except of sugar cane, sugar beet and cotton). The data set has a spatial resolution of 5 arc-minutes by 5 arc-minutes. Format: ASCII-grids (global, 5 arc-minute) or text files (country data).
UNEP's GEO Yearbook 2003 (UNEP, 2004) characterizes problems related to reactive nitrogen (nitrogen overloads in some areas and nitrogen deficiencies in other areas of the globe) as an emerging global environmental issue. Global modelling and scenario analysis may help to investigate linkages and feedbacks between global change and water pollution, and to identify appropriate management options. To get an overview of the present-day global situation of nitrogen input and fate and to derive scenarios of the future that simulate the impact of global change (climate, population, agriculture, waste water treatment, etc.), the global model WaterGAP-N is being developed. WaterGAP-N will simulate the input and fate of terrestrial nitrogen, including the input from diffuse (industrial fertilizer and manure, biological fixation, and atmospheric deposition) and point sources, and the transport of dissolved N and its loss by denitrification in soil and groundwater as well as in surface waters (rivers, lakes, wetlands). With a spatial resolution of 0.5°, the model computes the N loads in each cell as well as the input to the oceans. Here we present first results of WaterGAP-N and show how the model will be used to derive management options for large-scale nitrogen pollution on the background of the SRES scenarios of the Intergovernmental Panel on Climate Change (IPCC).
Heat is considered to be a major stress limiting crop growth and yields. While important findings on the impact of heat on crop yield have been made based on experiments in controlled environments, little is known about the effects under field conditions at larger scales. The study of Deryng et al (2014 Global crop yield response to extreme heat stress under multiple climate change futures Environ. Res. Lett. 9 034011), analysing the impact of heat stress on maize, spring wheat and soya bean under climate change, represents an important contribution to this emerging research field. Uncertainties in the occurrence of heat stress under field conditions, plant responses to heat and appropriate adaptation measures still need further investigation.
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