Food securityWarming will disturb nutrients balance in drylands, affecting food production
Drylands cover about 41 percent of Earth’s land surface and support more than 38 percent of the world’s population. As the world’s population grows, people will increasingly rely on marginal lands — particularly drylands — for production of food, wood and biofuels. Trouble is, an increase in aridity due to global warming will disturb the balance of nutrients in the soil and reduce productivity of the world’s drylands, a landmark study predicts. Increasing aridity is associated with a reduction in carbon and nitrogen in the soil and an increase in phosphorus.
An increase in aridity due to global warming will disturb the balance of nutrients in the soil and reduce productivity of the world’s drylands, which support millions of people, a landmark study predicts.
The research was conducted by a global collaboration of scientists who carried out the same studies of 224 dryland sites in sixteeen countries on every continent except Antarctica.
A UNSW release reports that in Australia, woodland sites near Mildura in NSW were studied by University of New South Wales’s (UNSW) Adjunct Professor David Eldridge, of the School of Biological, Earth and Environmental Sciences, who is a member of the international research team.
Other sites included areas of the Negev Desert in Israel, the Pampas lowlands in Argentina, and the Altiplano highlands of Peru. Rainfall at the sites ranged from 100 to 800 mm per year, and all soil samples were analyzed in the same laboratory in Spain.
The research shows that increasing aridity is associated with a reduction in carbon and nitrogen in the soil and an increase in phosphorus.
The results are published in the journal Nature.
“Drylands cover about 41 percent of Earth’s land surface and support more than 38 percent of the world’s population,” says Eldridge, who also works for the NSW Office of Environment & Heritage.
“As the world’s population grows, people will increasingly rely on marginal lands — particularly drylands — for production of food, wood and biofuels. But these ecosystems will be severely affected by imbalances in the cycle of carbon, nitrogen and phosphorus.”
A worldwide decrease in soil moisture ranging from 5-15 percent has been predicted for the 2080-2099 period.
Phosphorus in rocks and sediments is released into the soil by weathering, and levels are expected to increase as soils become drier and erode more.
This increase in phosphorus will be accompanied by reductions in carbon and nitrogen, which are more dependent on biological processes such as litter decomposition, photosynthesis and nitrogen fixation. Reduced plant cover will also exacerbate this effect.
“Plants need all of these elements, in the correct amounts and at the right times, but increasing aridity will upset this balance, leading to a breakdown in essential soil processes,” says Eldridge.
— Read more in Manuel Delgado-Baquerizo et al., “Decoupling of soil nutrient cycles as a function of aridity in global drylands,” Nature 502 (31 October 2013): 672–6 (doi:10.1038/nature12670)
