Vines are Choking Forests' Ability to Capture Carbon

Vines, causing them to lose carbon, are literally choking tropical forests, which are often underappreciated for their value in capturing carbon and battling climate change.

Tropical forests cover a mere seven percent of land surface and yet hold 30 percent of the world's terrestrial carbon, making them naturally efficient carbon cleaners. New research by Smithsonian scientists shows increasingly abundant vines could hamper this potential.

This is the first study to demonstrate that plant competition is directly affecting ecosystem-wide carbon uptake.

Lianas, or woody vines, found in Panama are the culprits, reducing net forest biomass accumulation by nearly 20 percent - and that's a "conservative" estimate according to researchers.

"This paper represents the first experimental quantification of the effects of lianas on biomass," lead author Stefan Schnitzer said in a press release. "As lianas increase in tropical forests, they will lower the capacity for tropical forests to accumulate carbon."

Previous research by Schnitzer and others found that, for unknown reasons, lianas are growing in tropical forests worldwide. Scientists suspect rainfall, but lianas are even cropping up in forests that haven't experienced any change in weather patterns.

Lianas climb trees to reach the forest canopy where their leaves blot out the sunlight required for tree growth. They account for 25 percent of the woody planets in a typical tropical forest, but unfortunately do not make up for the carbon lost because of their choking abilities.

Researchers reported that lianas were responsible for reducing tree biomass accumulation by nearly 300 percent.

"Scientists have assumed that the battle for carbon is a zero-sum game, in which the loss of carbon from one plant is balanced by the gain of carbon by another. This assumption, however, is now being challenged because lianas prevent trees from accumulating vast amounts of carbon, but lianas cannot compensate in terms of carbon accumulation," Schnitzer said.

"If lianas continue to increase in tropical forests, they will reduce the capacity for tropical forests to uptake carbon, which will accelerate the rate of increase of atmospheric carbon worldwide," he concluded.