Much of the time we focus primarily on the climate and how it is affecting our ecosystems. However, in doing so, we manage to overlook issues that we have brought with us as we’ve conquered other lands for centuries; invasive plants.
A new study to be published in the Proceedings of the National Academy of Sciences that non-native trees are encroaching upon rainforests. As a result, nutrients are lost to the non-natives which are often more aggressive, and thus change the rainforests natural ecological structure.
Led by Gregory Asner of the Carnegie Institution’s Department of Global Ecology, the research team used new remote sensing technology on aircraft to survey an area more than 220,000 hectares (850 square miles) in size of Hawaiian rainforest. Using instruments aboard the Carnegie Airborne Observatory (CAO) they were able to penetrate the forest canopy and essentially create a “CAT scan” of the ecosystem.
“Invasive tree species often show biochemical, physiological, and structural properties that are different from native species,” says Asner. “We can use these ‘fingerprints’ combined with the 3-D images to see how the invasives are changing the forest.”
This is the first time that technology such as this has been used to track invasives in Hawaii.
Hawaii’s ecosystem is roughly made up 50/50 of native and non-native flora, including 120 species of plan that are considered highly invasive. The ohia tree (Metrosideros polymorpha) makes up much of Hawaii’s undisturbed rainforests, but as time goes by, trees such as the tropical ash (Fraxinus uhdei) and the Canary Island fire tree (Morella faya) are intruding.
These two invasive species have a substantial detrimental effect on the native understory plants. Both the tropical ash and the Canary Island fire tree create a much heavier canopy than the ohia tree, and thus deprive the ground level plants of the much needed light.
“All of our invasive species detections were made in protected state and federal rainforest reserves,” says Asner. “These species can spread across protected areas without the help of land use changes or other human activities, suggesting that traditional conservation approaches on the ground aren’t enough for the long-term survival of Hawaii’s rainforests.”
“These new airborne technologies, which are sensitive enough to discern saplings and young trees, may make the problem more tractable,”comments study co-author Flint Hughes of the US Forest Service. “They allow scientists to probe the make-up of forests over large areas and detect invasions at earlier stages.”
Photo Courtesy of stevecadman via Flickr