Scientists are warning the dangers of climate change will be more wide-reaching than rising sea levels and wilder weather, with new research suggesting the nutrition levels of staple foods will fall as the amount of carbon dioxide in the atmosphere rises.

Experts fear climate change will erode decades of progress battling global malnutrition unless a solution can be found.

Carbon dioxide is a major factor driving global warming, but it is also the essential ingredient that allows plants to harness the energy of the sun.

New research published in the journal Nature suggests vegetation can have too much of a good thing.

Samuel Myers from Harvard University's Center for the Environment in the United States headed the research and says important crops such as rice and wheat will be affected.

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"Rising concentrations of carbon dioxide in the atmosphere are threatening global human nutrition by reducing the amounts of very important nutrients for human health in important food crops like rice, wheat and soy beans," he said.

"In particular, we found significant reductions in zinc, iron and protein."

Rice and wheat are two of the major crops used to feed the more than 7 billion humans around the world.

Dr Myers says nutritional changes in those grains in the future risk making a currently significant problem worse.

"There are roughly 2 billion people around the world who suffer from these deficiencies, and ultimately zinc deficiency affects our immune functions," he said.

"So, much of the burden of disease is calculated through early child mortality from infectious diseases like malaria and diarrhoea, pneumonia, measles. For iron deficiency, we see anaemia, but we also see sharp increases in maternal mortality, loss of IQ, reduced work productivity and, when you put all those things together, we calculate about 63 million life years to be lost annually, just in iron and zinc deficiency alone."

Yield increases, protein and zinc levels drop

The study's results are based on trials of six common crops at sites in the US, Japan and Australia.

Glenn Fitzgerald co-authored the study and runs a carbon dioxide testing program at Horsham for Victoria's Department of Environment and Primary Industries.

His team grew wheat and field peas in a specially adapted open field.

"Currently, future levels are around 400 points per million, and we're elevating them to 550, which is predicted for 2050," he said.

"That's done through a series of horizontal pipes that are joined in – we call it a circle, but it's really an octagon or eight-sided shape. There are eight pipes, and they get raised up on posts as the crop grows so that they sit just above the top of the crop and inject CO2.

"It's all computer-controlled in terms for wind speed, direction and central concentration of CO2," he said.

Dr Fitzgerald says the research builds on previous work showing higher carbon dioxide makes some plants grow more quickly.

He says it now appears that quantity comes at the expense of quality.

"It does depend on environment, rainfall, temperature et cetera, but here at Horsham, we're seeing, on average, an increase of about 20 to 25 per cent increase in yield, but you also get then this 5 to 10 per cent decrease in protein and zinc and iron concentrations," he said.

Scientists seek solutions, look to other crops

Those in the developing world are more susceptible to falling nutrition levels in staple plants because they are less likely to have regular access to other foods to fill the gap.

Dr Fitzgerald says they are now looking at potential solutions, including breeding new varieties.

Stable crops such as rice are more likely to be impacted by climate change, according to scientists. ( Matt Brann )

"If we target, more specifically, trying to increase the protein concentration in the micronutrients through breeding, then perhaps we can counteract some of these negative impacts that are occurring due to CO2," he said.

"Another way of doing that potentially is through nitrogen management. Can we add nitrogen fertilisers at the right time or in the right way, meaning slow-release fertilisers or foliate fertilisers et cetera, in order to counteract that negative impact of carbon dioxide?"

However, with the long lead time needed to develop new varieties, alternative staples may also need to be considered.

Dr Fitzgerald says the study suggests crops such as corn may be less-affected.

"It's a different kind of photosynthesis, where the plant takes in carbon and uses sunlight to grow and develop," he said.

"These crops have evolved to be more efficient already in their uptake of carbon dioxide, so adding carbon dioxide doesn't necessarily stimulate them in terms of growth.

"However, we do see some changes in, again reduction in protein and micronutrients, but not as severe as in other crops."