Tree frog at Sungei Buloh Wetland Reserve in Singapore. Credit: Nir Sinay
Tree frog at Sungei Buloh Wetland Reserve in Singapore. Credit: Nir Sinay

When I was little, one of my favorite books was a picture book about rainforests that took the reader through all the layers of the tropical rainforest — from the ground on up to the canopy — and the plants and animals that live there. The idea that entire worlds existed one on top of the other like this was fascinating to me.

A study recently published in the journal Proceedings of the Royal Society B has provided new insight into these strata and what the future may hold for them as the climate changes. Led by Brett Scheffers of James Cook University in Australia, the researchers climbed hundreds of trees in the rainforests of Singapore and the Philippines — some more than 160 feet tall — to collect data on a variety of tree frogs and other canopy species. They found that just as biodiversity exists in gradients of latitude and elevation, the vertical strata of the rainforest are also a type of climatic gradient. And, just as we’re seeing more adaptable species shift their range by moving north or by moving uphill as the climate changes, these arboreal species can adjust to the climate by moving up or down the canopy layers.

In fact, the study’s authors find that this allows these frogs and other tree-dwelling species to take advantage of a wider habitat range because as the habitat changes in elevation they can move up or down the trees accordingly. The same species of frog that lives in the canopy at one elevation might call the understory home a little further downhill.

Philippine tree frog Rhacophorus pardalis
Rhacophorus pardalis, a tree frog of the Philippines. Credit: Thomas H Brown

But, as temperatures continue to rise and the climate becomes drier, we can expect to see more of these species descending from the trees at higher and higher elevations — a process the study’s authors have dubbed “flattening” — all that vertical biodiversity getting pushed to the ground. According to the research, these species’ descent from the trees could lead to an 80 percent increase in density on the ground. That’s a lot of increased competition for resources.

“We discovered a whole new dimension to biodiversity on Earth, but in doing so, we uncovered new consequences of climate change,” says Scheffers in a James Cook University statement. “The Earth’s rainforests are certainly not flat, but if citizens and governments do not take the necessary actions to prevent strong changes in climate … they could be.”

That’s why we’re telling President Obama that forests need to be a priority in his Climate Action Plan since they help mitigate climate change and need our help to stay healthy. You can tell him, too, by signing our letter.