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Freshwater shortage could double climate change effects on agriculture

The loss of freshwater supplies, which has led to a large shift from irrigation-fed fields to rain-fed fields, could lower output estimates for crops by as much as 43 percent.

By Ananth Baliga

Global water shortages could double the effects of climate change on agricultural output, said a report based on the analysis of hydrological, agricultural and climate models.

It has been known for sometime that climate change will affect food production numbers, dropping output for crops like soybean, rice and maize by almost 43 percent. But further analysis of hydrological models estimate that this drop could be made worse by depleting freshwater supplies and the reversion of 20 to 60 million hectares of irrigated fields to rain-dependent fields.

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"It's a huge effect, and an effect that's basically on the same order of magnitude as the direct effect of climate change," said lead author Joshua Elliott, a research scientist with Argonne National Laboratory. "So the effect of limited irrigation availability in some regions could end up doubling the effect of climate change."

Agricultural and hydrological models have incorporated the effects of the Earth's warming but since they were designed for different purposes researchers never looked at the crossover effects of each model. Elliot and other researchers fed each type of model with similar data and were able to make these predictions about the future demand for freshwater irrigation.

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Climate change, according to previous models, alone would have accounted a loss of between 400 and 2600 petacalories of food supply, 8 to 43 percent of present day levels. One petacalorie is ten to the power fifteen calories. But if you factor in the freshwater supplies the loss increases to 600 to 2900 petacalories of food supply.

But while some parts of the world like the U.S., India and China could face face such shortages other parts may end up with a surplus of water and researchers said that equitable redistribution and use of this water could lessen the negative effects on crop output.

"We found that maximal usage of available surplus freshwater could end up ameliorating between 12 and 57 percent of the negative direct effects of climate change on food production," Elliott said.

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[Argonne National Laboratory] [PNAS]

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