Umbrella species management may have unforeseen consequences
Conservationists often focus habitat management efforts on one particular high-profile species, known as an “umbrella species,” with the aim of indirectly supporting other species that share the same ecological community, but a new study has revealed that this is not always the best strategy.
Researchers at the University of Wyoming focused an analysis on the Greater-Sage Grouse and its neighboring songbird species. Shrub mowing is a strategy used to protect sage-grouse, which require less shrubs and more grass and flowering plants during chick-rearing season.
The team tracked the numbers and nesting success rates of three songbird species before and after shrub mowing in central Wyoming. They collected data in sites that had not been mowed for comparison.
Two of the species which use shrubs for nesting, Brewer’s Sparrows and Sage Thrashers, had no nests where shrubs had been mowed. In these areas, it could be decades before shrubs have recovered enough for nesting. In addition, the overall abundance of Sage Thrashers was reduced by 50 percent after shrub mowing.
The third species examined in the study, Vesper Sparrows, were found to be more abundant in areas that were mowed extensively.
“The umbrella species concept is an appealing shortcut,” said study lead author Jason Carlisle. “However, when conservation practitioners go beyond protecting the umbrella species’ habitat and start manipulating habitat conditions to meet the needs of the umbrella species, they risk harm to other species that also rely on those areas.”
Because shrub mowing only covered a region of about five square kilometers in this particular case, the researchers explained that the benefits would likely outweigh the costs. However, the study authors highlighted a need for improved overall monitoring of umbrella-species management.
Russell Norvell is an Avian Conservation Program Coordinator at the Utah Division of Wildlife Resources who was not involved in the study.
“It is clear that the observed effects on ‘background’ species are not consistent across the range of potential beneficiaries, and that the assumed benefits do not accrue to many,” said Norvell.
“It is likely these effects will persist, given the relatively slow growth rates in this arid system. While the conservation of Greater Sage-Grouse habitats across its range is likely to encompass much good, local habitat manipulations driven by unexamined assumptions or uninformed by landscape context have much to prove.”
The research is published in The Condor: Ornithological Applications.
Image Credit: J. Carlisle