Trees spreading across the savannah could have dramatic impact on Earth

Treeless landscapes are becoming more wooded, which could result in a drastic shift in global temperatures.

While vast areas of woodland such as rainforests are increasingly under threat from the climate crisis, researchers from the University of Edinburgh have discovered something else is happening in other parts of the world: land that is typically wild and treeless is becoming increasingly wooded.

In a paper published to the journal Global Ecology and Biogeography, the researchers found that trees and shrubs are spreading across the tundra and savannah, transforming these vast plains and the fragile biodiversity within them.

The dramatic changes to these regions – which account for approximately 40pc of the world’s land – could alter the planet’s carbon balance and climate system, the researchers said. This is because trees store carbon, provide fuel for fires and influence how much of the sun’s heat is reflected back into space.

In Arctic tundra, spanning parts of northern Canada, the US and northern Europe, shrub plant cover has increased by 20pc over the past 50 years, the study found. This expanding shrub cover could raise soil temperature in the tundra, leading to the thawing of permafrost. Such an event would release nearly half of the world’s soil carbon.

Largest study of its kind

Meanwhile, in the savannah regions of the world such as in Africa and Australia, shrub and tree cover rose by 30pc over the past 50 years, while there was also an increase in rainfall.

To come to these conclusions, the researchers carried out the largest global woody cover change study of its kind to date. This involved comparing temperature and rainfall data with more than 1,000 records of plant coverage from almost 900 sites across six continents.

The study also found that wildfires and animal grazing patterns are affecting shrub and tree cover. This adds variables to our understanding of the future of the tundra and savannah regions, showing they are more complex than previously thought.

“This research indicates the far-reaching effects of climate change across the planet,” said Mariana García Criado, who led the study.

“Uncovering the ways in which different landscapes are responding requires collaboration among scientists, and cooperation with local peoples to better understand the changes we’re seeing and their impacts from different perspectives.”