Climate Change Threatens Cloud Forest Ecosystem
December 14, 2012

Costa Rica Cloud Forest Ecosystem At Risk From Climate Change

April Flowers for - Your Universe Online

A research team from the University of California, Berkeley, has discovered that tropical montane cloud forest trees drink water from clouds, directly through their leaves. There is just one small problem with this fact, the clouds necessary for the trees survival are disappearing due to climate change.

Declines and disappearances of cloud forest animals such as frogs and salamanders have already been correlated to changes in cloud cover.

"The study highlights the vulnerability of this rare and already endangered ecosystem to climate change,” said Todd Dawson, UC Berkeley professor of integrative biology.

The trees in a cloud forest gain some water through their roots, as other trees do. It isn't enough, however, to sustain the trees in what is essentially a very dry area, despite the constant fog or cloud cover. The leaves in a tropical montane cloud forest are constantly bathed in clouds, keeping them wet. When the moisture of the soil is not enough, the leaves of the most common cloud forest trees drink this cloud water.

“Many cloud forests experience an annual dry season when the primary water source isn´t rain, but rather, the moisture from the clouds,” he said. “This is when the trees are most likely to draw water in through their leaves," said Greg Goldsmith, a graduate student in Dawson's lab.

The team worked in Monteverde, Costa Rica, to study patterns of leaf wetness caused by the clouds. They set up small plastic "leaves" that used changes in the voltage of an embedded electrical circuit to detect moisture. Miniature sensors, installed on the branches of cloud forest plants, were used to tell whether water was entering the leaves when they were wet.

“The textbooks teach us that water enters roots, moves up the trunk and into the branches, then finally exits the leaves. That´s true, but it´s not the whole story,” Goldsmith said. “With our sensors, we observed water entering the leaves and actually moving back down the branches toward the trunk.”

The new findings build upon previous work by Dawson demonstrating a similar phenomenon in California redwoods.

The current study found that not all species of trees are able to drink the same amount of cloud water.

“The trees that are drinking the most water through their leaves may be more vulnerable to decreases in cloud cover resulting from rising temperatures,” said Goldsmith.

“The study provides a clear demonstration of the interactions between clouds and cloud forest plants and will serve as a cornerstone for future research on the effects of climate change on tropical montane cloud forest ecosystems,” Dawson added.

The findings of the new UC Berkeley study will be published next year in the journal Ecology Letters.