Lianas are taking over the rainforests – and it’s visible from space
by Rianne Lindhout, Leiden University
May 6, 2025
Tropical forests annually absorb roughly the amount of CO₂ emitted by the whole of Europe. They also house around half of the world’s biodiversity. However, their contribution to climate regulation and biodiversity is under threat—not only from deforestation but also from an extraordinary surge in lianas. Ecologist Marco Visser from Leiden’s Centre for Environmental Sciences (CML) explains: ‘Lianas can smother and kill trees. When they dominate, the forest becomes choked, and mainly lianas continue growing over fallen trees.’
During his doctoral research in 2016, Visser was the first to model lianas as if they were infectious diseases. ‘Lianas—such as passionflowers and numerous other species—can be compared to tapeworms. They intercept trees’ resources and can more than double tree mortality.’ At CML, Visser now supervises PhD candidate Manuela Rueda-Trujillo, who has analysed hundreds of liana studies. Their paper, published last summer, reveals that the increase is not confined to South and Latin America, as previously thought, but is happening wherever tropical forests exist. ‘A liana pandemic has been raging for over thirty years, with their prevalence rising by 10 to 24 percent every decade,’ Visser states.
Lianas are rapidly expanding their territory in tropical forests, sometimes suppressing tree growth entirely in certain locations. In such areas, forest regeneration halts, and carbon storage can decline by as much as 95 percent. ‘That’s almost equivalent to deforestation’, Visser says. He attributes this to rising atmospheric CO₂ levels. ‘All plants grow faster with more CO₂, but lianas benefit even more. They cheat—they don’t invest in structural support, borrowing it from trees instead, and their leaves require less energy and nutrients to produce.’ A liana can quickly climb to the canopy, spread a leafy cover over tree crowns, and steal all the sunlight for itself.
On 28 April Visser published research demonstrating that lianas are visible from space. Collaborating with American and British colleagues, he has now shown why this is the case. Visser developed mathematical models predicting how light interactions occur. ‘Then, we used cranes to access treetops in Panama to measure leaf properties. Our findings confirmed the models were correct.’
Keep reading: https://www.universiteitleiden.nl/en/news/2025/05/lianas-are-taking-over-the-rainforests—and-its-visible-from-space
Read the Ecology paper: https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecy.70082