The Latest Threat to Tropical Rainforests is... More Trees

invasive trees in hawaii

Images courtesy of Gregory Asner/Carnegie Institution

Never let it be said that we at TreeHugger, out of our unconditional love for trees, judiciously avoided recognizing the threat posed by invasive tree species... to other trees (cue the sound of crickets chirping). Yes, according to a new study published in the Proceedings of the National Academy of Sciences by scientists at the Carnegie Institution, non-native trees have been steadily invading Hawaii's lush tropical rainforests - putting their basic ecological structure (and resources) at great risk.

invasive albizia trees

Gregory Asner of the Department of Global Ecology led the project, using remote sensing technology on an aircraft to survey the invasive species' impact on Hawaii's 850 sq. mi of rainforest. The result, seen above and on the first page, was the "CAT scan" image of the forest, which helped the scientists map its complete 3-D structure and identify key plant species; the red/pink blotches depict the invasive species while the green/blue blotches depict the island's natural flora, dominated by the ohia tree.

The scientists observed that the stands of two invasive species in particular - Fraxinus uhdei and Morella faya - formed much denser canopies than did the ohia trees, resulting in less light filtering to the forests' lower levels and blunting the growth of native understory plants. These observations were all made in protected state and federal forest reserves, suggesting that the species were able to widely disperse without the help of anthropogenic activities.

Asner and his colleagues hope the innovative technology will help Forest Service officials and local authorities more effectively monitor the make-up of forests and nip future invasions in the bud.

Via ::ScienceNOW: Trouble in Paradise (news website)

See also: ::Report Offers Recommendations to Help States Address Invasive Forest Pests, Pathogens, ::Zimbabwe Fights Back Against Invasive Species