Rockström Johan
UNESCO-IHE, PO Box 3015, 2601 DA Delft, The Netherlands.
Philos Trans R Soc Lond B Biol Sci. 2003 Dec 29;358(1440):1997-2009. doi: 10.1098/rstb.2003.1400.
This paper quantifies the eco-hydrological challenge up until 2050 of producing food in balance with goods and services generated by water-dependent ecosystems in nature. Particular focus is given to the savannah zone, covering 40% of the land area in the world, where water scarcity constitutes a serious constraint to sustainable development. The analysis indicates an urgent need for a new green revolution, which focuses on upgrading rain-fed agriculture. Water requirements to produce adequate diets for humans are shown to be relatively generic irrespective of hydro-climate, amounting to a global average of 1,300 m(3) cap(-1) yr(-1). Present food production requires an estimated 6,800 km(3) yr(-1) of consumptive green water (5,000 km(3) yr(-1) in rain-fed agriculture and 1,800 km(3) yr(-1) from irrigated crops). Without considering water productivity gains, an additional 5,800 km(3) yr(-1) of water is needed to feed a growing population in 2,050 and eradicate malnutrition. It is shown that the bulk of this water will be used in rain-fed agriculture. A dynamic analysis of water productivity and management options indicates that large 'crop per drop' improvements can be achieved at the farm level. Vapour shift in favour of productive green water flow as crop transpiration could result in relative water savings of 500 km(3) yr(-1) in semi-arid rain-fed agriculture.
本文对到2050年实现粮食生产与自然中依赖水的生态系统所产生的商品和服务保持平衡这一生态水文挑战进行了量化。特别关注了占世界陆地面积40%的稀树草原地区，在那里水资源短缺对可持续发展构成了严重制约。分析表明迫切需要一场新的绿色革命，其重点是升级雨养农业。结果显示，为人类生产充足饮食所需的水量相对具有普遍性，与水文气候无关，全球平均为每年每人1300立方米。目前的粮食生产估计需要每年6800立方千米的消耗性绿水（雨养农业中为每年5000立方千米，灌溉作物为每年1800立方千米）。如果不考虑水分利用效率的提高，到2050年为养活不断增长的人口并消除营养不良，还需要额外5800立方千米的水。结果表明，这些水的大部分将用于雨养农业。对水分利用效率和管理选项的动态分析表明，在农场层面可以实现大幅度的“每滴水产量”提升。通过将水汽转移到有利于作物蒸腾的生产性绿水流中，半干旱雨养农业每年可相对节水500立方千米。
