Lead researcher Brett Scheffers of the Centre for Climate Change and Tropical Biology at James Cook University in Townsville, Australia, said “our findings suggest that the biodiversity that lives in the tree tops of rainforests may be pushed toward the cooler and wetter ground as the climate warms.”
If this happens, it could alter the way rainforests function, he warned.
Almost half of all known species in the tropics live in rainforest canopies, but according to the researchers climate change may create an extinction zone in the lowlands that starts in the canopy and moves down towards the ground. As the Earth continues to warm, this zone will then expand upward in elevation.
Mr Scheffers said that species were already moving uphill or towards the poles in search of cooler and wetter climates as the Earth warms and dries from climate change. But he and his colleagues are the first to suggest that before this happens, species will first move out of the trees and towards the ground.
To collect data, Mr Scheffers and a large group of field researchers traversed a mountain in the tropical rainforests of the Philippines in search of frogs and other animals that live in the treetops.
The JCU researcher said that a major reason why their study is unique is that rainforests consist of towering trees that are incredibly difficult to access, with some more than 50 metres in height.
“This discourages many researchers from conducting canopy research. Over the course of several months, we had to climb hundreds of trees to get our data,” Scheffers said.
The researchers “flattening” forest hypothesis is based on a century-old debate over what causes patterns of biodiversity.
Their report says that rainforest vegetation creates a climate gradient over a distance of just 20 to 30 metres that is far steeper than the changes in climate that may occur over hundreds of meters of elevation or kilometres of latitude.
Biodiversity in tropical rainforests was found to organize along this height gradient—from the tops of trees down to the ground. The organization of species from ground to canopy changes with altitude as species tend to move upwards in the rainforest strata as elevation increases.
“We discovered a whole new dimension to biodiversity on Earth but in doing so we uncovered new consequences of climate change. We should carefully monitor for downward movements of rainforest species as this could be an early warning that rainforests are under stress,” he said, adding that while the rainforests are certainly not “flat” they could be if we do not take the necessary actions to prevent strong changes in climate.
JCU School of Earth and Environmental SciencesThe School of Earth and Environmental Sciences is located in Townsville and Cairns, central to the Great Barrier Reef and the Wet Tropical Rainforests World Heritage Areas, and at the gateway to the world class mineral fields of north-eastern Australia, Papua New Guinea and the West Pacific.
The school is proud of its multidisciplinary approach, its international outlook, and its extensive network of collaborations with private and government organizations, linked to a strong research tradition and a dynamic learning environment.