Vines strangle forests in hot weather and threaten planet’s cooling ‘carbon sink’

As Earth records its hottest year on record, a global research collaboration has found that warmer temperatures are a key factor in woody vines taking over the world’s forests, threatening their vital role in cooling of the atmosphere by storing carbon.

Covering 44 countries on five continents, the study led by the University of the Sunshine Coast, published in Biology of global change identified which forests around the world are most vulnerable, based on their climate.

The identified hotspots are low-lying rainforests, examples of which can be found in East Africa, Vietnam, Colombia, the humid tropics of Australia, and many other locations around the world.

Professor Andy Marshall, from the UniSC Forestry Research Institute, said the team had confirmed a “tipping point” in the conditions that led to the dominance of the liana, a woody vine that chokes out trees and prevents them from growing, as it climbs to reach the forest canopy. .

This crucial time for forests already disturbed by logging, land clearing and other impacts occurs when the average annual temperature exceeds 27.8° Celsius and precipitation is less than 1,614 mm.

“Woody vines are increasingly taking over the world’s forests. For the first time, we have a global assessment that confirms that forest disturbance and climatic factors are the main drivers of liana dominance,” said the Professor Marshall.

“These results are critical to successfully restoring the world’s forests, allowing us to know where to focus our restoration efforts and future areas of concern in a changing climate,” Professor Marshall said.

“It is important to identify the environmental conditions under which lianas are likely to outcompete trees and block recovery in disturbed native forests around the world,” Professor Marshall said.

“In Australia, the coastal and lowland forests of northern Queensland are the most vulnerable…
This adds to the ongoing threat of deforestation which in Queensland is already greater than in any other developed country,” he said.

“With warmer temperatures and continued disturbance from logging and land clearing, the forest areas threatened by lianas around the world will only increase.”

Professor Marshall said the study was the culmination of more than 20 years of research and filled a critical gap in the understanding of grapevine dominance internationally.

“On my very first expedition to a rainforest in East Africa in 1998, I noticed these vines growing on all the trees and wondered what on Earth was happening and why no one was investigating “Since then, research has exploded in scale, but it’s mostly a local or regional approach,” he said.

This global study used “an unprecedented dataset” from 651 vegetation samples representing 26,538 lianas and 82,802 trees, from 556 unique locations around the world, from 83 research publications.

Twenty co-authors contributed to the research paper, representing research institutes from Australia, South Africa, the United Kingdom, Singapore, Panama, Brazil, the United States and China.

Threats to Earth’s carbon sink

Lead author Alain Ngute, who is studying forest recovery as part of his doctoral studies at UniSC, said the results showed lianas were better adapted to cope with climate change, including warmer temperatures. and lower precipitation, as well as other disturbances such as fires, logging and clearing.

Lianas dominate trees and hinder their ability to recover following disturbance, a situation that can persist for decades.

“Understanding how this situation varies over time in different climates is crucial for predicting responses of degraded forest landscapes and for guiding forest management strategies in the face of global environmental changes,” said Ngute.

The impact of these vines on the carbon sink was another critical area highlighted in the results.

Along with the ocean and soil, forests are the world’s largest carbon sinks, absorbing and storing carbon dioxide from the atmosphere.

Already severely affected by the loss and degradation of forests through tree felling, Mr Ngute said the findings suggest the vines add to the threat to the carbon sink by preventing trees from growing and slowing down forest regeneration following disturbance.

Looking for solutions

The next step is to find sensitive and effective solutions to help vines recover and help restore the global carbon sink.

However, Professor Marshall said large-scale clearing of vineyards was not the solution.

“We certainly wouldn’t want this work to lead to forest managers cutting all these vines out of their forests,” he said.

“Liana plays its role in the forest ecosystem and biodiversity by increasing soil fertility and carbon cycling, and can benefit other plants, animals, soils and overall ecosystem functioning, in intact forests and disturbed.

“It’s just that the human impact is so great in some areas, that it’s increasing in very large numbers, but not in a natural way.”

UniSC is continuing its research into the effects of vines on forests and how to manage their impact through Professor Marshall’s Forest Restoration and Climate Experiment. These results are the first step toward confirming the team’s recently published theory on global forest recovery from disturbance and vines.