Deforestation of the Amazon rainforest could accelerate as a result of the US-China trade war, researchers have warned.

Increased tariffs saw exports of US soya beans to China halved in 2018, creating a huge shortfall that could trigger extensive tree-felling in Brazil, experts say.

The study, from the University of Edinburgh and Karlsruhe Institute of Technology, warns that Brazil will be under pressure to provide up to 38 million tonnes of soya beans - used principally as livestock feed - for China each year.

Pressure to fill the shortfall could see Brazil increase its land used for crop production by up to 39 percent - 13 million hectares - according to the Food and Agriculture Organisation of the United Nations. Two decades of growth in the global soya bean market has already led to large-scale deforestation in Brazil's rainforests.

Political and legal controls that have prevented the expansion of soya bean production in the Amazon have recently been weakened, researchers say.

They warn that deforestation increased by 29 percent between 2015 and 2016. Brazil's newly elected president has also removed the land rights of many indigenous people.

China's Brazilian imports have increased by 2,000 percent in the past two decades. Researchers say it is highly likely that China's appetite for livestock feed and bioenergy will drive further increases.

By late 2018, 75 percent of China's soya-bean imports came from Brazil, meaning that the entire US shortfall was substituted with Brazilian crops.

With little prospect of China reducing its intake of soya beans, the study, published in Nature, suggests a range of measures to ensure no further loss of the Amazon rainforest.

Researchers say China and the US should acknowledge their roles in driving tropical deforestation and remove trade tariffs on the crop.

China could also seek a wider range of suppliers, including Argentina and Europe.

Researchers also urge Brazil to improve its environmental protection schemes by financially rewarding developers and businesses for not clearing forests.

Dr Peter Alexander, from the University of Edinburgh's School of Geosciences, said: "Governments, producers, regulators and consumers must act now. If they don't, the Amazon rainforest could become the greatest casualty of the US-China trade war."