Lianas are woody climbing plants that root in the ground but depend on other structures, usually trees, to reach the forest canopy. They are among the most influential players in tropical forests, making up roughly a quarter of woody stems in many areas and shaping everything from how much carbon a forest stores to which tree species survive. Despite looking like passive hangers-on, lianas are aggressive competitors with a suite of physiological tricks that let them thrive where most plants would struggle, and their numbers appear to be rising across the tropics.
What Makes a Liana Different from a Vine or a Tree
The word “liana” refers specifically to woody climbers. Herbaceous vines like morning glories or sweet peas share the climbing habit but lack the persistent woody stems that let lianas grow for decades, sometimes reaching lengths well over 100 meters as they snake through the canopy. What sets lianas apart from trees is not just their climbing habit but the internal architecture of their stems. When a liana latches onto a support, its wood undergoes dramatic changes: the water-conducting vessels become larger, the wood produces fewer dense support fibers, and overall water-transport capacity increases compared to the same species growing without a support.1PubMed. Liana attachment to supports leads to profound changes in xylem anatomy and transcriptional profile of cambium and differentiating xylem This makes sense as a trade-off: a liana outsources its structural support to the host tree and reinvests the savings into a plumbing system that can move water and nutrients fast.
The climbing habit has evolved independently many times across the plant kingdom. Some families are dominated by lianas, including grape relatives, passionflowers, and certain members of the dogbane family.2Annals of Botany. Phenotypic correlates of the lianescent growth form: a review Different liana species use different strategies to climb: tendrils, twining stems, hooks, adhesive roots, or simply leaning and scrambling over neighboring branches. The end result is the same. The liana reaches the canopy light without investing heavily in a thick, self-supporting trunk.
The Dry-Season Advantage
One of the most consequential traits of lianas is their ability to keep photosynthesizing during seasonal drought, a period when many tropical trees slow down. In a study comparing lianas and trees in a tropical seasonal forest, lianas maintained about 87% of their wet-season photosynthetic rate during the dry season, while trees dropped to roughly 61%.3PubMed Central. Seasonal differences in leaf-level physiology give lianas a competitive advantage over trees in a tropical seasonal forest Lianas also used water and nitrogen more efficiently during drought, meaning they squeezed more carbon out of every unit of resource consumed.
How do they pull this off? Part of the answer is that many lianas tap deeper soil water during the dry season. Research in seasonal forests in China found that lianas shifted to using a higher proportion of deep soil water when surface moisture dried up, which allowed them to maintain leaf water status as good as or better than neighboring trees.4PubMed. Water-use advantage for lianas over trees in tropical seasonal forests Lianas also showed strong stomatal control, tightly managing the pores on their leaves to maximize carbon gain while minimizing water loss. During the wet season, when water is plentiful, lianas ran their photosynthetic machinery at full blast, with higher maximum rates and sap flow than trees. Then in the dry season, they throttled back less than trees did. This combination of aggressive wet-season growth and resilient dry-season performance helps explain why lianas are so abundant in forests with pronounced dry periods.
Isotope analysis of xylem water from a French Guiana forest supports this picture of underground resource partitioning. Liana water signatures were distinct from those of neighboring trees, indicating that the two growth forms were drawing from different soil layers even when growing side by side.5Tree Physiology. Liana and tree below-ground water competition—evidence for water resource partitioning during the dry season
How Lianas Compete with Trees
Lianas are not benign passengers. They compete fiercely with their host trees, and the effects are large enough to reshape forest structure. A field experiment in Panama found that tree saplings growing in the presence of lianas accumulated only about 17–19% of the aboveground biomass of saplings growing without liana competition.6Journal of Ecology. Disentangling above‐ and below‐ground competition between lianas and trees in a tropical forest That is a staggering reduction. Surprisingly, the study found that belowground competition, the fight for water and soil nutrients, was the primary driver. Aboveground shading mattered too, producing shorter and thicker-stemmed saplings with stunted crowns, but saplings that experienced only belowground liana competition fared just as poorly as those dealing with both above- and belowground competition combined.
Modeling work has reinforced the idea that water competition between lianas and trees is more important than scientists once thought. Simulations from two contrasting Neotropical forest sites showed that water limitation was the dominant competitive force at the drier site and during dry-season months even at the wetter site.7PubMed Central. Unraveling the relative role of light and water competition between lianas and trees in tropical forests: A vegetation model analysis Light competition was the main factor only in young, regrowing forest patches during the wet season. This challenges the long-standing intuition that canopy light competition is the whole story. Lianas are fighting a two-front war against their hosts, and the underground front may be the decisive one in most conditions.
The Carbon Problem
Tropical forests are the largest land-based carbon sink on Earth, so anything that changes how they store carbon has global implications. Lianas are a problem for carbon storage because they reduce the growth and survival of the large trees that hold the vast majority of a forest’s carbon. Across 145 tropical forests worldwide, higher liana abundance was linked to lower carbon stocks in large trees, which store about 90% of total forest carbon.8PubMed Central. Carbon stocks in tropical forests decrease with liana density
A large-scale liana-removal experiment in Panama quantified just how big this effect can be. Three years after lianas were cut, the forests where lianas had been present showed about 76% less net aboveground carbon uptake than forests freed from lianas.9PubMed Central. Lianas reduce carbon accumulation and storage in tropical forests Lianas also changed how carbon was allocated within the forest. In forests with lianas, more than half of aboveground net primary production went to leaves rather than wood. In liana-free forests, that balance flipped, with about 44% going to woody stems. Since leaves decompose quickly and return their carbon to the atmosphere within a year or two, liana-heavy forests were effectively cycling carbon faster rather than locking it up in long-lived wood.
More recent monitoring on the same Panamanian island (Barro Colorado Island) found that canopy liana density increased over 8% in a decade, and canopy lianas outnumbered canopy trees by nearly four to one. Where liana density rose, tree carbon storage fell, and vice versa.10PubMed. Does increasing canopy liana density decrease the tropical forest carbon sink? The authors suggested this dynamic could help explain the weakening carbon sink observed in American tropical forests in recent years.
A Pantropical Increase
The trend on Barro Colorado Island is not an isolated case. A meta-analysis synthesizing data from across the tropics found that liana abundance is increasing at an average rate of roughly 1.7% per year, translating to somewhere between a 10% and 24% increase per decade.11PubMed. Global increase of lianas in tropical forests This trend was robust against publication bias and extended beyond the Neotropics, where it was first documented, to include forests in Africa and Asia as well.
Long-term plot monitoring in undisturbed Amazonian forests tells a consistent story. Liana stem counts increased by about 1% per year over the monitoring period, a small annual rate that compounds into large changes over decades.12PubMed. Long-term changes in liana abundance and forest dynamics in undisturbed Amazonian forests Liana biomass, however, rose more slowly and the increase was not statistically clear in that study. This means forests are gaining more liana stems, but the individual lianas may not be getting bigger on average, possibly because of turnover or because younger, smaller lianas are the ones proliferating.
Why the increase? The leading hypotheses center on rising atmospheric CO₂, more frequent or more intense droughts, and accelerating forest disturbance dynamics. Rising CO₂ can benefit lianas disproportionately because they invest more of their resources into rapid leaf and stem growth rather than structural wood. More frequent droughts favor lianas because of their dry-season physiological advantages described earlier. And more disturbance creates more canopy gaps, the very environments where lianas excel. These factors likely work together, though disentangling their individual contributions remains an active area of research.
What Happens When Lianas Take Over a Canopy Gap
When a large tree falls in a tropical forest, the gap it creates is usually described as a regeneration opportunity, a patch of light where young trees race skyward. Lianas can disrupt that process. In some gaps, lianas proliferate so densely that tree seedlings and saplings are suppressed, and the gap stalls in a low-canopy state dominated by a tangle of climbing stems. Research on Barro Colorado Island estimated that at least 7.5% of newly forming gaps follow this liana-dominated pathway, and many of these stalled gaps persist for well over a decade.13Journal of Ecology. The impact of lianas on tree regeneration in tropical forest canopy gaps: evidence for an alternative pathway of gap‐phase regeneration
An eight-year experiment that removed lianas from treefall gaps demonstrated the magnitude of their suppressive effect. With lianas gone, tree growth increased by 55%, recruitment of new tree stems rose by 46%, and tree species richness jumped by 65%.14PubMed. Lianas suppress tree regeneration and diversity in treefall gaps The hit was not spread evenly across tree species. Shade-tolerant species, the ones that form the backbone of mature forest, were disproportionately harmed. Pioneer species that specialize in gap colonization were less affected. The implication is that heavy liana loads do not just slow forest recovery, they can steer the recovering community toward a different species composition, potentially one with fewer of the slow-growing, long-lived trees that store the most carbon.
An Unexpected Role in Storms
Not everything lianas do to trees is harmful. One intriguing finding from a Belizean forest exposed to tropical cyclones suggests that lianas can stabilize trees during high winds. Liana-laden trees grew more slowly and died at higher rates under normal conditions, consistent with the competitive effects described above. But as wind exposure increased, those differences shrank. Mortality risk for liana-free trees rose more steeply with increasing cyclone exposure, while liana-laden trees appeared comparatively buffered.15Journal of Ecology. Cyclones reduce growth and mortality differences between liana‐laden and liana‐free trees in Belize The mechanism could involve lianas physically tethering tree crowns to their neighbors, effectively creating a web that distributes wind stress, or it could reflect the fact that lianas tend to associate with certain cyclone-resistant tree species. Either way, it complicates the simple narrative of lianas as purely parasitic.
Why Lianas Are Rare Outside the Tropics
Anyone who has walked through a temperate forest has noticed the relative scarcity of thick woody climbers compared to a tropical jungle. The leading explanation involves freezing. Lianas depend on wide water-conducting vessels for their efficient plumbing, and wide vessels are vulnerable to air bubbles that form when water inside them freezes and thaws. These bubbles, called embolisms, can block water flow and effectively shut down the stem’s hydraulic system.
Research comparing liana performance across climates found that species growing in cold environments had vessels about three times narrower than their tropical counterparts, and their water transport efficiency dropped by more than 25-fold. Despite these narrower, “safer” vessels, cold-climate lianas still lost over a third of their hydraulic conductivity to freeze-thaw events.16PubMed Central. The functional mechanism behind the latitudinal pattern of liana diversity: Freeze-thaw embolism reduces the ecological performance of liana species This trade-off between efficiency and safety helps explain why liana diversity drops sharply as you move away from the equator.
The picture has some nuance, though. A study of cool-temperate forest lianas in Japan found that the vulnerability story is not quite so simple. Some temperate lianas were no more vulnerable to freeze-thaw damage than neighboring trees, and their ecological success in cooler regions seemed to depend more on their ability to restore hydraulic function after winter than on resisting damage in the first place.17PubMed. Hydraulic Strategies of Cool-Temperate Trees and Lianas Against Freeze-Thaw Embolism: Is Cold Winter More Severe on Lianas? In other words, some lianas survive cold winters not by preventing embolisms but by repairing them come spring. This recovery mechanism may be why a handful of liana species manage to persist in temperate forests, even though they never approach tropical abundance.
Leaf Chemistry and Nutrient Cycling
Liana leaves are chemically distinct from tree leaves in ways that ripple through the forest nutrient cycle. Globally, liana leaves have higher concentrations of chemicals associated with light capture and metabolism, averaging about 15–17% higher than trees on a mass basis. At the same time, liana leaves contain about 9% less structural and defensive compounds.18PubMed. Contrasting leaf chemical traits in tropical lianas and trees: implications for future forest composition This chemical profile, more nitrogen and less tough structural tissue, fits a “live fast” strategy. Lianas build cheap, productive leaves, then drop them.
The consequences for decomposition are predictable. A multisite experiment across the Neotropics found that liana leaf litter decomposed faster than tree leaf litter. Liana litter had higher nitrogen content, was thinner, and was less tough, all traits that make it easier for microbes and soil fauna to break down.19Journal of Ecology. Liana litter decomposes faster than tree litter in a multispecies and multisite experiment Faster litter decomposition returns nutrients to the soil more quickly, which could accelerate the nutrient cycle in liana-heavy forests. But faster decomposition also means faster release of the carbon stored in that litter back to the atmosphere, reinforcing the pattern seen in the carbon studies: lianas push the forest’s carbon budget toward rapid cycling and away from long-term storage.
Lianas and the Insects That Patrol Them
Lianas do not exist in isolation from the animal community. One less obvious ecological role involves their relationship with ants. Many tropical plants produce nectar from glands located outside their flowers, called extrafloral nectaries, which attract ants. These ants patrol the plant and attack herbivorous insects, providing an indirect defense. A study in a Brazilian seasonal forest found that liana species growing on host plants that also bore extrafloral nectaries benefited from shared ant patrols. The climbing plant had a more diverse ant community visiting it, more individual ants, and nearly three times less leaf damage from herbivores compared to lianas growing on hosts without nectaries.20PubMed. Plants with extrafloral nectaries share indirect defenses and shape the local arboreal ant community This kind of indirect mutualism adds another layer to the ecological web that lianas participate in. They are not just competing with trees; they are embedded in a network of animal interactions that can influence their growth and survival.
Liana Cutting as a Forest Management Tool
Given the evidence that lianas suppress tree growth and reduce carbon storage, forest managers have started to consider liana cutting as a practical intervention, particularly in selectively logged tropical forests. Logging opens up the canopy and creates the kind of disturbed conditions where lianas proliferate, often smothering the remaining crop trees that loggers expect to harvest in future cutting cycles.
An analysis of selectively logged forests estimated that cutting lianas around just five future crop trees per hectare, applied across the roughly 250 million hectares of selectively logged tropical forest worldwide, could yield an additional 0.8 billion tonnes of CO₂ in carbon removals over 30 years. The direct cost would be well under one dollar per tonne of CO₂.21Forest Ecology and Management. Liana cutting in selectively logged forests increases both carbon sequestration and timber yields At that price, liana cutting would rank among the cheapest forest-based carbon interventions available. The treatment also increases future timber yields, giving a financial incentive to logging concessions. Whether this approach works at scale and across different forest types remains to be tested, but the combination of low cost, carbon benefit, and timber value has attracted serious attention from tropical forestry researchers.
Of course, cutting lianas is not ecologically free. Lianas provide food and travel routes for arboreal animals, contribute to canopy connectivity that lets primates and other animals move through the forest without descending to the ground, and their fast-decomposing litter helps cycle nutrients. Any large-scale cutting program would need to weigh these tradeoffs. The ethnobotanical record also offers a reminder that lianas have direct human uses: surveys in regions like southern India have documented dozens of liana species used in traditional medicine, spanning numerous plant families.22Scholars Academic Journal of Biosciences. Ethnomedicinal Uses of Climbers and Woody Lianas Species in Alluri Sitarama Raju District, Andhra Pradesh, India The most famous liana of all in terms of human use is probably ayahuasca (Banisteriopsis caapi), a South American liana central to indigenous ritual practice, though countless other species yield fibers, dyes, and construction materials in tropical communities worldwide.