April 29, 2008
"It's a double whammy," Osvaldo Sala explained. "We not only are disturbing our planet by putting more carbon into the atmosphere, but we're reducing the ability of ecosystems to capture and store it." Sala is the director of the Environmental Change Initiative and the Sloan Lindeman Professor of Biology at Brown.
The Brown scientists conducted their study for six years in Patagonia. They divided an area into ninety plots then began to systematically remove native species from each plot and chart the changes in the plot's productivity. Productivity dropped as species were removed.
The scientists believe that productivity is linked to the diversity of species because of "niche complementarity". In other words, in an intact environment each species has evolved its own niche without interrupting other species' niches. This harmony between species allows them to positively interact with each other and fully utilize the resources of a given space.
In the experiments "the water is the same, the nitrogen is the same, the sunlight is the same, what is different is the diversity of the plants," said Sala. Artificial landscapes proved far less productive than natural ones. According to the paper: "In contrast [with artificial landscapes] natural ecosystems presented mature individuals, populations, and species coexisting for long periods of time in natural soils without chemical treatments and low artificial disturbance regimes."
The findings appear to have important ramifications beyond plant species, since high biodiversity of plants depends on non-plant species. Insects, birds, and bats are major pollinators for plant species; some plant species depend on a single insect or animal species for pollination. Therefore, to have a truly productive ecosystem all of the region's biodiversity must be retained.
According to the paper, "this result supports previous findings and also suggests that the effect of biodiversity in natural ecosystems may be much larger than currently thought." The findings give wildlife conservationists a new powerful argument for species protections. Many biologists believe that we are currently entering a mass extinction, entitled the Holocene Extinction Event, estimations range from 20-50 percent of species becoming extinct within approximately hundred years. The reasons are varied for species extinction but include climate change, habitat loss, pollution, the bush-trade, invasive species, and the trafficking of species for medicinal products.
Citation: Pedro Flaumbaum and Osvaldo E. Sala (2008). "Higher effect of plant species diversity on productivity in natural than artificial ecosystems". Proceedings of the National Academy of Science in the United States of America, April 22nd 2008.
blog comments powered by Disqus