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Increase water harvesting in Africa - Meeting global food needs requires strategies for storing rainwater and retaining soil moisture to bridge dry spells, urge Johan Rockström and Malin Falkenmark

Ensuring that the world's food needs are met by 2050 will take a doubling of global food production. To improve agricultural yields on that scale will require a radical rethink of global water management strategies and policies. Meeting global food needs requires strategies for storing rainwater and retaining soil moisture to bridge dry spells, urge Johan Rockström and Malin Falkenmark in the latest article published 19 March in the journal "Nature"

Some excerpts from the article...

  • Sub-Saharan Africa is the epicentre of this challenge. The region's population is set to more than double by 2050 to almost 2.5 billion, or 25% of the world's projected  
  • Half of its current one billion inhabitants lives in extreme poverty, one-quarter is undernourished, and one-fifth faces serious water shortages.
  • Although almost two-thirds of the population are rural, agriculture on much of the land is limited by scarce, variable and unpredictable water resources
  • Ninety-five per cent of sub-Saharan agriculture depends on 'green water': moisture from rain held in the soil.
  • In large parts of the continent, most rain evaporates before it generates 'blue water', or run-off, so little of it recharges rivers, lakes and groundwater.
  • Arid deserts and semi-arid savannahs comprise 40% of the region's land area.
  • These receive too little surface run-off (less than 100 millimetres a year) to grow maize (corn), rice, millet and sorghum (which requires at least 400 mm per year) using irrigation alone.
  • Future rainfall will be more variable and could be 25% lower in many semi-arid regions if average global temperatures warm by 2 °C above pre-industrial . Management of green water for rain-fed, small-scale farming is integral to eradicating hunger. But it is missing from the draft United Nations Sustainable Development Goals (SDGs), which will be agreed in September.

In the article the authors propose an approach for the SDG goal that will improve water security, address hunger and poverty and enhance carbon storage. Retaining more rainwater in soils and storing run-off would bridge dry spells that last weeks, the major challenge to rain-fed food production. For longer droughts, social and economic strategies are needed to assure food security.

  • Regions in which irrigation is not viable include highly populated places such as Africa's Sahel region, northern China and central India.
  • In sub-Saharan Africa, almost 500 million people live in dry zones — deserts, grasslands and bush savannahs — in countries such as Mali, Niger and Zimbabwe.
  • Another 245 million live in slightly wetter zones with forest savannahs, for example in large parts of Tanzania and Zambia, where run-off is still too low to irrigate fields (see 'African drylands' map!!!!!Please scroll down the article here  ...an excellent visual presentation