Abstract
The insufficiency of water resources to meet the needs of food production is a pressing issue that is likely to increase in importance in the future. Improved understanding of historical developments can provide a basis for addressing future challenges. In this study we analyse how hydroclimatic variation, cropland expansion and evolving agricultural practices have influenced the potential for food self-sufficiency within the last century. We consider a food production unit (FPU) to have experienced green–blue water (GBW) scarcity if local renewable green (in soils) and blue water resources (in rivers, lakes, reservoirs, aquifers) were not sufficient for producing a reference food supply of 3000 kcal with 20% animal products for all inhabitants. The number of people living in FPUs affected by GBW scarcity has gone up from 360 million in 1905 (21% of world population at the time) to 2.2 billion (34%) in 2005. During this time, GBW scarcity has spread to large areas and become more frequent in regions where it occurs. Meanwhile, cropland expansion has increased green water availability for agriculture around the world, and advancements in agronomic practices have decreased water requirements of producing food. These efforts have improved food production potential and thus eased GBW scarcity considerably but also made possible the rapid population growth of the last century. The influence of modern agronomic practices is particularly striking: if agronomic practices of the early 1900s were applied today, it would roughly double the population under GBW scarcity worldwide.
Highlights
The possible insufficiency of land and water resources to meet the needs of humanity, those of agriculture, is a pressing issue that is currently affecting roughly a third of the world’s population (Kummu et al 2010, 2014, Hoekstra et al 2012)
By 1965, this number had more than doubled, and 29% of the world population lived in food production unit (FPU) that were under green–blue water (GBW) scarcity, which had spread to new regions in e.g. Southeast Asia and Southern Africa
Roughly 990 million people lived in FPUs that did not have enough water resources to produce the reference food supply for their inhabitants—the remainder may have been imported by trade, or local food supply may have been less than 3000 kcal cap−1 d−1 on average
Summary
The possible insufficiency of land and water resources to meet the needs of humanity, those of agriculture, is a pressing issue that is currently affecting roughly a third of the world’s population (Kummu et al 2010, 2014, Hoekstra et al 2012). Projected future developments, such as population growth (Gerland et al 2014) and increasing climatic and hydrologic variability (Coumou and Rahmstorf 2012, Ward et al 2014), are likely to further aggravate resource scarcity with implications for food security (Foley et al 2011, Steffen et al 2015). The resources to feed the growing population have gotten scarcer relative to demand and may have limited sufficient food production in the past
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