A warming climate could affect the stability of alpine grasslands in the Tibetan Plateau, threatening the ability of farmers and herders to maintain the animals that are key to their existence, warned a team of researchers from the US and China.

Though temperature changes could destabilise the fragile ecosystem of the area, variations in rainfall appear to have no similar effect, according to the study published in the journal Nature Communications. 

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The study involved two varying factors likely to change with a warming climate — temperature and rainfall — in test plots over a five-year period. 

"We were concerned about the variability of the total community plant cover over time," said Lin Jiang, Professor at Georgia Institute of Technology in the US.

"Significant warming could reduce the stability of the grasslands, which would increase the variability of plant biomass production that could be a significant issue for people living in the region. We believe the effects of climate change could be particularly dramatic in this area," Jiang said. 

The Tibetan Plateau is an area of about 2.5 million square kilometres in which summertime high temperatures seldom rise above 25 degrees Celsius and night time temperatures could drop below freezing even in the summer. 

Because of the altitude, temperature extremes and high winds, more than two-thirds of the Plateau is grassland which is used for grazing yak, sheep and other animals.

About 9.8 million people live in the area, which is also the source for several of Asia's major river systems.

"Our results suggest that under a warmer climate, the ecosystem would provide less forage production in drought years, and more biomass production in wet years – which is undesirable," said Jin-Sheng He, Professor at Peking University in Beijing, China. 

The researchers found that the stability of the grasslands was affected not by the richness of plant species, but by the effects on dominant species and the asynchrony of the species.

"We found that climate warming lowers stability through increasing species synchrony in which the biomass of a few dominant species increased while that of most rare species declined," said He. 

"That indicates the alpine grasslands that have well adapted to cold environments owing to their long-term evolutionary history may be jeopardised in the future," He said.