The loss of large predator animals across the globe is having unanticipated impacts on processes as diverse as human disease dynamics, wildfires and biogeochemical cycles, according to new research by an international team of scientists that includes UBC zoologists.
The report, published today in the journal Science by two dozen researchers from institutions in the United States, Europe and Canada, calls for increased scientific scrutiny of the 'top-down' ecological role played by large predator species.
"Most ecosystems in the world require predators to be in the system because they control the next level down--the plant eaters," says Tony Sinclair, a professor with the UBC Department of Zoology and one of the authors of the study.
"If you take away the predators then things start to go wrong. Too many plant eaters remove the plants, having all sorts of anticipated and unanticipated impacts. The problem is that humans are systematically removing the predators--in the ocean they are the big fish, on land they are the large predators like lions and leopards."
While widely viewed as an ethical issue, the study compiles recent research revealing the extensive cascading effects of the disappearance of 'large apex consumer' in marine, terrestrial and freshwater ecosystems worldwide.
The researchers note the impact of the viral disease rinderpest in East Africa in the 1890s which decimated the large plant feeders, an example of a species loss that in turn increased plant biomass and fueled increased wildfires. The effects are still being seen over a century later.
The study also points to health issues caused by increases in baboon populations in parts of sub-Saharan Africa. As populations of the baboons' natural predators--lions and leopards--were reduced, increased populations of baboons contributed to the spread of intestinal parasites among humans.
"Many practicing ecologists still view large animals in general, and apex consumers in particular, as ecological passengers riding atop the trophic pyramid but having little impact on the structure below," note the authors.
"These findings emphasize the urgent need for interdisciplinary research to forecast the effects of trophic downgrading on process, function and resilience in global ecosystems."
The study was supported by the Natural Sciences and Engineering Research Council of Canada. The report's principal author is James Estes, University of California, Santa Cruz, and UBC zoologist Jonathan Shurin also contributed to the study.
Science
www.sciencemag.org
Tony Sinclair, UBC Zoology
www.zoology.ubc.ca/person/sinclair
