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Better “green water use” can reduce future food crisis |
If overall water resources in river basins were acknowledged and managed better, future food crises could be significantly reduced. This is concluded in a recent analysis carried out by researchers from Stockholm Resilience Centre, Stockholm Environment Institute (SEI) and Potsdam Institute for Climate Impact Research.
The researchers quantify for the first time the opportunities to use effectively both “green” and “blue” water (see box below) to adapt to climate change and to feed the future world population. Their study, entitled “Future water availability for global food production: the potential of green water for increasing resilience to global change” was recently published in the journal Water Resources Research. The findings change fundamentally the conventional bleak predictions for future water scarcity in the world.
Can lift billions out of water poverty
The current approach to water management considers only blue water, that is,
river discharge and groundwater. This limits the options to deal with increasing water scarcity and water risks induced by climate change. Under those conditions, over three billion of the current world population are estimated to suffer from severe water scarcity.
The new analysis which additionally accounts for green water, that is water in the soil that stems directly from rainfall, suggests that the actual number is under one billion. It also shows that wise water management can lift billions out of water poverty.
“This opens a new area of investments for climate adaptation and a window to achieve a much needed new green revolution in poor countries in the world. Our analysis shows that many water-short countries are able to produce enough food for their populations if green water is considered and managed well”, says the analysis.
 – Much of the past debate regarding various water-scarce regions focused on the absence of water rather than the opportunities linked to the presence of water, says lead author Johan Rockström, executive director for the centre and SEI.
An enormous untapped potential
The study applied the latest global hydrological modelling and climate scenarios to analyse down to local village scale how much water farmers actually can access.
– Normally this leads to a very gloomy result as only blue water resources for irrigation are considered but by including the rainfall that infiltrates the soil, which forms the basis for all food production in rainfed agricultural systems, but we discovered an enormous untapped potential due to massive unproductive losses of blue and green water, Rockström says.
Basis for a new green revolution
The study shows how better use of green water can form the basis for a new green revolution. It may also provide the basis for building resilience towards more frequent and intense floods, droughts and dry spells under human-induced climate change.
Many countries that are classified as chronically blue water-short, have enough blue-plus-green water to produce a standard diet for their populations. Kenya, for example, has plenty of unused or not well-managed green water to benefit from.
– Not even by 2050 and under climate change will the country become water-short if both blue and green water are managed well, says says Holger Hoff, researcher at the Potsdam Institute for Climate Impact Research.
Box: “Blue” and “green” water
The concept of blue and green water was coined by Malin Falkenmark for an FAO conference on water and agriculture in 1995.
“Blue water” is the liquid water in rivers, lakes and ground water. It is linked to irrigation-based agriculture.
“Green water” is the water that feeds the system as rain and forms soil moisture that is absorbed by plants (and then exhaled as vapour flow). In Africa, 95% of the agriculture is rain-fed in this way by ‘green water’.
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Major water challenges ahead
The analysis shows that by 2050, 59 percent of the world population will face blue water shortage, and 36 percent will face green-plus-blue water shortage. This means that 36 percent of the world population will live in countries that will not have enough water to produce their own food.
– Unfortunately, despite the new opportunities arising from our green-blue analysis, our findings show that humanity will still face major water challenges by 2050 in certain regions of the world, says Rockström.
Building water resilience
Co-author Louise Karlberg calls for a broadened green-blue approach in order to identify options for better water resilience building.
– Provided the green water was managed better, for example by methods to increase plant transpiration at the expense of unproductive soil evaporation, even under climate change good options would exist to build water resilience in many countries even without expanding cropland, she says.
/Sturle Hauge Simonsen
Source:
Rockström, J., M. Falkenmark, L. Karlberg, H. Hoff, S. Rost, and D. Gerten 2009. Future water availability for global food production: The potential of green water for increasing resilience to global change. Water Resour. Res., 45, W00A12, doi:10.1029/2007WR006767
14 February 2009. |
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