Lianas are taking over the rainforests, and it's visible from space

Summary

Credit: Pixabay/CC0 Public Domain A pandemic of lianas is sweeping through tropical forests, reducing their ability to store carbon and limiting their role in mitigating climate change. Two recent studies from Leiden University highlight the issue. "We now understand why lianas are visible in satellite imagery," say the researchers. 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 Center 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." A liana pandemic for more than 30 years 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 Ph.D. candidate Manuela Rueda-Trujillo, who has analyzed hundreds of liana studies. Their paper, published last summer in Global Change Biology, 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 more than 30 years, with their prevalence rising by 10% to 24% 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%. "That's almost equivalent to deforestation," Visser says. He attributes this to rising atmospheric CO₂ levels. "All plants grow faster with more CO...