Lianas are long, woody vines that are rooted in the ground and use trees as vertical support as they grow. They can be found in a range of ecosystems across the planet, but are most abundant and diverse in tropical forests.
Lianas are important structural components of tropical forests and also play a key role within the ecosystem. In tropical forests, between 10 and 45% of woody stem growth occurs in the form of lianas.
On the one hand, in addition to being an important element in the forest regeneration process, they serve as “highways” for the circulation of animals among the treetops, and their fruits serve as food for many species.
On the other hand, lianas compete intensively with trees. They function as structural parasites on major tree species, limiting their growth, altering their vital functions, and increasing their mortality. Where they grow in particularly high densities, they can monopolize the nutrients in soils and slow the regeneration of the forest (Makowski, 2009). As the great English naturalist Charles Darwin observed, this means that an overabundance of woody vines can have negative consequences, not only on tree communities, but also on the overall ecosystem and the general health of the forest.
Some scientists believe that deforestation and climate change are affecting the delicate balance of the forest ecosystems in which the many species of liana play a vital role. In areas where forests have been disturbed by human activity –so-called “secondary forest”- lianas have been found to be more abundant than in undisturbed, so-called virgin forests, like those we help to protect in the Tambopata region of southern Peru, where we operate our ecotourism vacation programs.
Such seemingly subtle variations in the composition of tropical forest ecosystems can have profound repercussions on life in the forest, affecting both flora and fauna. Where lianas thrive in disturbed forest, once they reach the canopy their dense leaf cover spreads sideways, competing successfully with tree species for available sunlight, and multiplying the initial effects of human activity. In the battle for sunlight in tropical forests, it is those trees which remain free of lianas that gain an advantage.
Lianas are particularly important to the life of the forest thanks to the services they provide to several species of tropical fauna. Many animals that use lianas to travel through the forest would otherwise have to move around on the ground, where they would fall prey easily to predators. Many of these same animals also feed on the fruits or flowers of certain species of liana. The animals that depend on lianas range from ants to lizards, rodents, sloths and monkeys.
In South America, including Peru, humans have also traditionally benefited from some liana species. Ayahuasca (Banisteriopsis caapi), a psychoactive plant used for centuries in spiritual medicine ceremonies and now popular with many travelers from the west, is a species of liana. So, too, is uña de gato (Uncaria tomentosa), better known in English as “cat’s claw”. The root bark from uña de gato is used in herbal medicine, and in our modern world it is also marketed as a dietary supplement.