Global study shows impact of climate change on rangelands

A team of international researchers, including Dr Matt Tighe from the University of New England (UNE), has found that the arid rangelands which cover around 70% of Australia may be profoundly altered by the impact of climate change. This will be due to a relatively small change in soil nutrient levels over the next 100 years, as reported in the journal Nature.

“The study is the first to examine this type of effect at a global scale,” said Dr Tighe. Information was collected from 224 dryland test sites across six continents in 16 countries.

“[The study] has found that as systems became more arid, carbon and nitrogen levels were reduced, while phosphorus levels in the soil increased,” said Dr Tighe.

The researchers explained, “It has been suggested that the [carbon, nitrogen and phosphorus] cycles could become uncoupled under rapid climate change because of the different degrees of control exerted on the supply of these elements by biological and geochemical processes.

“Climatic controls on biogeochemical cycles are particularly relevant in arid, semi-arid and dry sub-humid ecosystems (drylands) because their biological activity is mainly driven by water availability. The increase in aridity predicted for the 21st century in many drylands worldwide may therefore threaten the balance between these cycles, differentially affecting the availability of essential nutrients.”

Dr Tighe says it is hard to predict exactly what changes this will have on the agricultural production capacity of these areas, though as around 38% of the world’s human population rely on semi-arid, arid and dry sub-humid environments, the result will surely have wide-reaching impacts.

“A rapidly expanding world population means farmers and graziers are under continual pressure to grow more and more from the limited supply of land available for agriculture,” Dr Tighe said. “This research reveals that these changes to our landscape could mean many of the farming practices now used to gain maximum productivity from the land may no longer provide the same results.

“As soil carbon levels decline, the Earth’s soil will tend to revert to resemble simpler ecological systems. Essentially, climate change will cause the soil to ‘reset’ to a system that has less complex biological interactions.”

Dr Tighe said the results follow UNE’s partnership in a global collaborative network of researchers, who have been examining dryland systems for several years.