Water management could boost crop yield, but not enough, study suggests
A team of German and Swedish researchers has found that moderate on-farm water management using certain strategies could increase global crop production by a total of 19%. However, further substantial improvements in agriculture would be needed to meet the food demands of the world's growing population. The findings are part of the team's modelling study published in the open-access journal Environmental Research Letters.
This research was partly funded under the 'Sustainable Development, Global
Change and Ecosystems' Theme of the Sixth Framework Programme (FP6) through the
ENSEMBLES ('ENSEMBLE-based predictions of climate changes and their impacts')
'Use of water in agriculture is a key problem for the 21st
century: without improvements neither the consequences of climate change will be
manageable nor [will] the demand of 2 or 3 billion additional people for food be
met,' says co-author Professor Wolfgang Lucht of the Potsdam Institute for
Climate Impact Research (PIK) in Germany. 'In this study we therefore
investigated whether there are realistic opportunities to close the emerging gap
in water supply for agriculture at least partially for many world regions. The
results are quite encouraging.'
Using a vegetation-water model, the
researchers identified two key strategies: the reduction of soil evaporation and
the harvesting of rainwater. Through mulching and different tillage systems,
water evaporation from the soil could be cut by 50%, at the same time turning
the unproductive evaporation into productive plant transpiration. According to
the researchers, such measures alone could increase global crop yield by 2% to
25%. The most promising regions for this strategy are the semi-arid regions of
the midwestern United States, the Sahel, southern Africa and central Asia.
In addition, the researchers suggest that rainwater should be harvested
in ponds or with the help of dikes and subsurface dams to compensate for dry
periods. In this way, global crop yields have the potential to be augmented by
between 4% and 31%. 'However, the detrimental effects of climate change could
reduce global crop production by almost 10% by 2050,' explained PIK's Stefanie
In order to meet the food needs of a world population of 10
billion in 2050 - an estimate of the Intergovernmental Panel on Climate Change
(IPCC) - the portion of land used for crops would have to be expanded by 10
million square kilometres (km2) to 25 million km2 worldwide. This would also
result in a substantial increase of freshwater consumption by 4,500 cubic
kilometres (km3) to 13,300 km3.
'However, in many regions of the world
that already face limits of water availability, that is not an option,' pointed
out Dr Dieter Gerten, hydrologist at PIK. 'Instead, we need to think of better
ways to use the water that is there.'
The researchers conclude that even
large-scale water management efforts on current cropland will not be sufficient
to ensure that the food needs of the growing global population are met. 'This
evidence poses crucial questions about trade-offs between future land and water
use for irrigated and rain-fed agriculture, natural ecosystems and bioenergy,'
'It furthermore highlights the need for exploring and
combining all options of more efficient irrigation and/or expansion of irrigated
agriculture, of plant breeding and genetic development, and of more effective
virtual water trade.'