Plant Biodiversity Shields Natural Ecosystems From Man-Made Perils

April Flowers for – Your Universe Online
A new study led by integrative biologists at the University of Guelph warns of the perils inherent in an ecosystem breakdown. The findings of the study, which appeared as the cover story in today´s issue of the journal Nature, suggest that resource managers and farmers should not rely on single crop monocultures, no matter how stable they may appear to be. The team suggests instead that farmers should cultivate the growth of more kinds of plants in fields and woods as a buffer against sudden ecosystem disturbances.
Based on a ten-year study, the team´s findings lend scientific weight to moral and esthetic arguments for preserving species biodiversity and confirm that greater species diversity in an area helps ecosystems avoid irreversible collapse after human disturbances.
“Species are more important than we think,” said Professor Andrew MacDougall. “We need to protect biodiversity.”
Previous studies have relied on short-term, artificial study plots. The Guelph team, along with colleagues from the University of British Columbia, studied long-standing pasture grasslands on southern Vancouver Island. Owned by the Nature Conservancy of Canada, the 10-hectare site is made up of oak savannah where fires have been suppressed for some 150 years.
To compare areas of mostly grasses with areas of mixed grasses and diverse native plants, the team chose to selectively burn plots. They found that seemingly stable grassland plots collapsed after one growing season and were subsequently overrun by invasive species of trees. The more diverse sites, however, were able to resist tree invasion.
Species diversity in the plots affected how the fire itself burned and spread as well. The team found that areas with more biodiversity had less persistent ground litter, which decreased the likelihood of high-intensity fires. In single-species plots where there was more more litter to serve as fuel, high-intensity fires were much more likely.
According to MacDougall, the study findings support the case for developing resource management strategies that increase biodiversity in both terrestrial and aquatic ecosystems. No matter how stable and productive a monoculture stand of trees or crops might appear, the team says it is almost inevitably more vulnerable to collapse than a well-diversified one.
Kevin McCann studies food webs and ecosystem stability. He says many ecosystems, including grasslands that may easily become either woodlands or deserts, are at “tipping points.”
“They’re a really productive ecosystem that produces year in and year out and seems stable and then suddenly a major perturbation happens, and all of that biodiversity that was lost earlier is important now,” said McCann.