Liberating trees from their burdens of woody vines (lianas) is an extremely cost-effective way to improve the economic value of managed forests and help mitigate climate change, according to new research published in Forest Ecology and Management by scientists from the University of Florida, The Nature Conservancy, Conservation International, and partner institutions.
The paper shows that strategic liana cutting, primarily in selectively logged forests, can substantially increase timber production and provide forest managers with access to voluntary carbon markets. To minimize biodiversity impacts the authors recommend limiting the number of trees liberated from lianas and propose a detailed approach to treatment application, monitoring, and carbon crediting.
Climate change and other human disturbances are causing woody vine infestations to intensify, especially in forests subject to selective logging. While lianas are fundamental components of most tropical and some temperate forest ecosystems, they decrease tree survival and growth rates, thereby decreasing timber yields in managed forests and reducing carbon storage wherever they are abundant. Conversely, dozens of previous experimental studies document that in response to liana removal, tree growth rates often double.
A “low-hanging” natural climate solution
Globally, lianas affect an estimated 250 million hectares of selectively logged forest. The authors calculated that liberating just five future crop trees (FCTs)—or trees destined for harvest—per hectare in these managed forests would remove 800 million metric tons of carbon dioxide (CO2) from the atmosphere over a 30-year period.
“Lianas are great, but they are also potent above- and below-ground competitors with trees,” says senior author Jack Putz, who is continuing his research at Australia’s University of the Sunshine Coast.
“Especially in selectively logged forests, cutting lianas on selected future crop trees would contribute to sustaining timber yields while having minimal impacts on biodiversity. In forests not destined for logging, liana cutting could increase tree fruit production while increasing carbon removal from the atmosphere.”
Liana cutting is easily incorporated into existing forest management practices, and the cost of the treatment is estimated at less than USD $1.00 per ton of CO2. This represents an attractive opportunity for countries to both meet their climate action goals, or Nationally Determined Contributions (NDCs), and—given current carbon market prices of $10-20 per ton of CO2—boost the economic potential of selectively logged forests.
“At a time when the impacts of forest carbon projects are being questioned more than ever, along comes liana removal, a novel and cost-effective approach to climate change mitigation that maintains the ecological integrity of forest ecosystems,” says Alex Finkral, forest investment manager and President and CEO of Eastwood Forests.
“Liana projects in high-biodiversity environments will generate high-quality carbon credits that will command price premiums.”
It is important to caveat that lianas provide critical ecosystem services, act as inter-crown pathways for canopy animals that do not fly, and some are important food sources for wildlife. To minimize the forest biodiversity-tree growth tradeoff, the authors recommend freeing no more than ten trees per hectare of their liana burdens, leaving lianas in the remaining trees untouched. Any biodiversity impacts should also be considered in the wider context of conservation benefits; keeping managed forests economically viable helps prevent their conversion to non-forest land uses.
Co-author Denver Cayetano, a forest biologist from Belize and Ph.D. student at the University of Florida, says this is a low-cost and easy-to-implement natural climate solution grounded in traditional knowledge that can also benefit local communities looking to participate in carbon markets.
“Most carbon projects require large upfront expenditures,” he says, “whereas in this case, owners of small tracts of forest can liberate a few trees and thereby contribute to climate mitigation.”
Natural climate solutions—activities designed to protect, restore, and improve the management of forests and other natural ecosystems so they can absorb and store more carbon—are a crucial part of addressing the climate crisis. Recent studies from the Nature Conservancy and others show that restoring and protecting nature could provide up to a third of the emission reductions needed by 2030, annually capturing up to 11 billion metric tons of CO2. Most of this emissions reduction would come from interventions in forests, particularly in Latin America, Africa, and Southeast Asia.
“Smart liana removal in managed forests is a climate no-brainer with a double win for climate at a cost of pennies per ton of carbon,” says study co-author Peter Ellis, Global Director of Natural Climate Solutions Science at The Nature Conservancy.
“If you’re looking for a ready-made ‘low-hanging’ natural climate solution, I can’t think of a better option.”
Selective liana cutting is an extremely cost-effective natural climate solution and a profitable forestry intervention that should be standard practice in managed forests where liana infestations are prevalent. The authors are now working with voluntary carbon markets programs, such as the Verified Carbon Standard (VCS), to create a streamlined carbon accounting process so that this climate-positive Improved Forest Management strategy can be implemented soon.
“Liana thinning can restore forests, improve local livelihoods, and help reverse climate change,” says Bronson Griscom, Conservation International’s Vice President for Natural Climate Solutions.
“For centuries we have been damaging forests and pumping CO2 into the atmosphere. Both activities have given lianas an advantage over trees and limited the ability of forests to pull CO2 out of the atmosphere. It’s time we flipped the script.”
The Nature Conservancy is a global conservation organization dedicated to conserving the lands and waters on which all life depends. Guided by science, we create innovative, on-the-ground solutions to our world’s toughest challenges so that nature and people can thrive together. We are tackling climate change, conserving lands, waters and oceans at an unprecedented scale, providing food and water sustainably and helping make cities more sustainable. Working in more than 70 countries and territories, we use a collaborative approach that engages local communities, governments, the private sector, and other partners. To learn more, visit nature.org or follow @nature_press on Twitter.