A new study involving Professor David Coomes from the Department of Plant Sciences has found that cutting lianas increases canopy height in regenerating logged forests three times faster than tree planting alone.
As the world faces the twin crises of climate change and biodiversity loss, researchers are trying to understand how to restore degraded forests to most effectively sequester carbon, benefit biodiversity, and promote sustainable land use. A new study published in Current Biology adds to this endeavor, finding that cutting vining plants called lianas dramatically boosts canopy height in previously logged forests in Borneo.
Lianas are a signature part of tropical forests, with their abundant flowers and fruits attracting insects, birds and mammals, and their looping woody vines creating natural bridges in the canopy.
But in logged or disturbed forests, lianas can grow out of control - and they aren’t always the most considerate of neighbours. Proliferating in sunlit gaps, lianas use trees as scaffolding to fast-track their way to the very top of the canopy, while their roots pull water and nutrients from the ground. This can smother trees and change the way they grow, inhibiting forest regeneration.
A number of studies have found that removing lianas by severing their stems can boost tree growth in disturbed forests; for example, a 2022 meta-analysis in Ecology and Evolution found that removing lianas more than doubled tree growth and biomass accumulation. So far, though, most of this research has been done in Latin America; less is known about tropical forests elsewhere.
Southeast Asia’s tropical forests are among the world’s tallest, with dipterocarp trees reaching 100 meters (about 330 feet) in height. Selective logging typically targets these giants, and because dipterocarp seeds don’t survive well in the soil, restoration often involves planting nursery-reared saplings. However, saplings take many years to reach the canopy, and, for the first few decades after planting, do little for the diminished forest structure.
Now, in a large-scale experiment in Borneo, researchers have found that cutting lianas turbocharges forest regeneration, with canopy height and carbon sequestration increasing three times faster following liana cutting, compared to planting saplings.
The findings offer tangible guidance on how to restore Borneo’s logged forests, according to Dr Toby Jackson, senior research associate at the University of Bristol and the study’s first author.
“This [liana cutting] could be a good way … and a reasonably cost-effective way, to go in and restore” selectively logged forests, Jackson said.
The study took place in Malaysian Borneo, and was part of the Sabah Biodiversity Experiment, a large ecological experiment covering 500 hectares (about 1,240 acres).
The study area’s secondary forests were logged once, in the 1980s, and are now a “slightly toned-down” version of the nearby primary forests in the Danum Valley, Jackson said: still rich in biodiversity, but with a lower canopy and more lianas.
To understand the impact of liana cutting on forest regeneration, the researchers set up two treatments. In 2002, they planted dipterocarp saplings in 4-hectare (10-acre) experimental plots across the study area, a treatment called enrichment planting. In some of those plots, they subsequently killed all lianas by cutting them. The researchers also established control plots where the forest was left to regenerate without intervention.
In 2013 and 2020, they mapped the study area and nearby primary forest using lidar, a system of rapid laser pulses that can build up extremely accurate 3D pictures of landscapes. The data allowed the researchers to compare changes in forest structure between the two experimental treatments (enrichment planting, and enrichment planting with liana cutting), control plots, and primary forest.
The differences were stark.
When freed from their liana load, forests grew taller faster, with a denser and more complex canopy, accumulating carbon three times faster than enrichment planting alone. Liana cutting resulted in an extra 27 centimetres (nearly 11 inches) of canopy height per year. The lidar data also revealed that increased growth and lower tree mortality were equally important in boosting canopy height.
“The intact canopy was growing faster after liana cutting. But also in the control plots, and in the enrichment planting plots, and in the primary forest, there’s more tree mortality,” Jackson said.
Cutting the lianas was relatively inexpensive - as much as 10 times cheaper than enrichment planting, the researchers estimate.
In lightly logged forests, such as those in the study area, liana cutting alone would likely be enough to give forests a boost, Jackson said. But he added that in more heavily logged areas, enrichment planting might be needed as well. The study also shows how financial resources can be allocated for the best results.
The study offers a “rare” comparison between two different restoration methods used in identical physical locations, and monitored over a long period of time, said Dr Catherine Finlayson, an associate scientist with Conservation International, a nonprofit, who wasn’t involved in the study.
Finlayson said she also liked how the researchers used lidar data to take a closer look at what was happening in the forest, especially for parameters like tree mortality, which are hard to track with conventional field-based studies.
“It’s a great experiment, and I think they’ve done some nice things with the lidar data as well,” Finlayson said.
Jackson noted that this study did not look at biodiversity, an important consideration when evaluating forest treatments, he said. Lidar data are an excellent way to look at changes in forest structure, and a good proxy for carbon sequestration, but don’t give any information on individual plant species, insects, birds, animals, or other facets of biodiversity, he said.
Biodiversity impacts are tricky to pin down, he added, and depend on what groups of species you’re looking at.
He said he suspects that cutting all lianas within a regenerating forest is “probably a bit extreme,” and a partial cut, designed to bring lianas back to a more natural pre-logging density, would be “kinder to biodiversity.” The team is awaiting results from a second experiment, designed to answer some of those questions, he said.
If done wisely, liana cutting could become a “massive part” of forest management, Finlayson said.
“[W]e need to make sure we’re doing it carefully and responsibly, and thinking about the biodiversity as well.” she said. “[I]t’s always a balance, but I think it could really improve the sustainability of forestry.”
She added the idea is that if liana cutting accelerates regeneration, forests will regain timber value more quickly and that the same land can be logged again, so that loggers won’t have to target new areas; more intact forests mean that over the long term, landscape-level biodiversity benefits. Liana cutting could also add value to forests in terms of carbon sequestration, and, as it’s a labor-intensive management technique, provide local employment.
Finlayson is now working on Conservation International’s Liana Impacted Forest Treatment (LIFT) pilot projects in Brazil, Peru and Indonesia. Through these pilots, she and her colleagues say they hope to move liana cutting from theory to practice by standardizing data collecting and monitoring factors like tree growth, carbon sequestration, and biodiversity responses.
One of the goals of this project is to figure out how to balance tree growth with biodiversity benefits. Some options include focusing on certain tree or liana species, only cutting lianas of a certain size, or leaving sensitive habitats, like riparian areas, aside.
“There’s lots of different ways you can kind of slice up the treatment activities to maximize the growth of the trees while minimizing any of the other impacts,” Finlayson said.
Reference: Jackson T, et al, 'Liana cutting accelerates the structural recovery of once-logged tropical forests at a fraction of the cost of tree planting.' Current Biology. DOI: 10.1016/j.cub.2026.04.056.
Image: A Malaysian field assistant cutting lianas with a machete at the Sabah Biodiversity Experiment. Killing lianas by cutting boosts tree growth and lowers tree mortality, the study found. Image courtesy of Gianluca Cerullo.
From an article by Ruth Kamnitzer originally published on the conservation and environmental news website, Mongabay, on 13 July 2026. Read the original article.