Securing enough water to grow crops to feed our increasing population is going to require innovation as climate instability worsens in the future.
The situation facing Cape Town in South Africa — a city running completely dry — is likely to become more commonplace if we can't find new ways to harvest water, and make it travel further.
Researchers now believe they are a step closer to developing crops that use significantly less water.
A team reporting today in the journal Nature Communications, have genetically engineered a test tobacco crop that uses 25 per cent less water for essentially the same harvest.
"We tested them in the field and we didn't see a big penalty — the plants were not significantly smaller than the wild type," said researcher Katarzyna Glowacka, from the University of Illinois, Urbana.
The researchers modified the expression of a protein that regulates the opening and closing of stomata — small pores on plant leaves that let in CO2 and let out oxygen and water.
They found that when they increased the expression of the protein, called Photosystem II Subunit S (PsbS), the stomatal opening was restricted and the plants lost less water, while still appearing to absorb similar amounts of CO2 — crucial to plant energy production.
"By overexpressing only one protein we could achieve something like 25 per cent, one-fourth better water efficiency, this is very big," Dr Glowacka said.
Food crops may be engineered to save even more water
The researchers used tobacco plants as the trial species because of its fast lifecycle, but believe the research can have wide applications because the PsbS protein is found in all plants.
"In tobacco it works and it should work the same way in other plants. In C4 plants, which are most [food] yielding plants like corn and sugarcane, it has even bigger promise," Dr Glowacka said.
C4 plants are more efficient at fixing CO2 during photosynthesis and the researchers think this means they will tolerate even greater manipulation of their stomata.
"Our next step is to look at C4 crops… like corn, soy bean, sugarcane, sorghum."
The tobacco research was carried out in controlled environments where plants were given plenty of water and sunlight.
To test whether the technology may be adapted to real-world scenarios, the researchers will need to carry out extensive subsequent studies.
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Although the research is in its infancy, University of Western Australia Institute of Agriculture chair and director Professor Kadambot Siddique believes the study is significant.
"It's definitely an important finding," he said.
"The challenge for all of us in agriculture is to produce more, especially in the next 50-70 years because there's a lot of demand, and water is the biggest challenge.
"With the predicted change in climate which is happening, we've seen that in Australia and in Cape Town and many other places, [rainfall is] declining in many places."
After years of drought, Cape Town in South Africa is only a few months away from "day zero" — when the city will completely run out of water.
But Professor Siddique warns it will probably be a number of years before agriculture will be able to use the research to reduce water consumption in crops.
"It's early days in the glasshouse with this," he said.
Professor Siddique said it was important to consider possible negative impacts of creating water-efficient crops.
"Sometimes what happens is that the photosynthesis can be reduced as well," he said.
Professor Siddique is recognised internationally as a leader in crop science and agriculture and his research includes developing legumes adapted to dryland environments, and working to increase wheat yield.
He said that selection pressure has driven some high yielding commercial crops toward higher water consumption, and it was important to develop more water efficient farming practices, including the use of GM crops, to feed our growing population.
"Australia is the driest human-inhabited continent in the world," he said.
"The prediction is that we'll need at least 75 per cent more food crops than what we produce now, by 2050.
"But we have our own limitations. Climate change is really happening and threatening Australia. So we need in this case definitely water-efficient [crops]."
Dr Glowacka agreed that water security will be a key challenge to feeding growing populations in a changing climate.
"By the end of this century, a lot of the most populated areas of the world will be constrained by water," she said.