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Making small changes to how we manage wildlife can have major benefits to wildlife communities

Written by Travis Gallo, 2014-2015 Sustainaiblity Leadership Fellow and Ph.D. Student in the Department of Fish, Wildlife and Conservation Biology.

Altering natural areas to benefit economically important wildlife, such as deer and elk, has been underway for centuries. Game management is widespread across the globe – from tree reductions in the United States to increase grasses and plants that deer and elk prefer to eat, to burning moorlands in Scotland to increase open areas for game birds – yet their effects on non-targeted animals and natural communities are poorly understood. For decades, this game management model has assumed that measures benefiting hunted species also positively affect all wildlife in the area. However, there is little evidence to support this notion. We found remarkably few studies that directly evaluated the effect of game management on non-targeted wildlife. Decisions based primarily on a single-species generally target a small subset of the animal community. With species going extinct at alarming rates, it is critical that we re-evaluate that assumption and investigate how land management decisions are impacting all wildlife – not just economically important species.

Here in Colorado, pinyon-juniper woodlands have been the objects of efforts to covert woodlands into grazing lands for livestock and big game species for the last half century. Pinyon-juniper woodlands are the third largest vegetative community in the United States – covering over 40 million hectares. These woodlands offer valuable resources – supplying food and shelter for woodland-dependent wildlife, food and fuel for humans, and forage for livestock. However, both pinyon and juniper trees have been expanding into grasslands and shrublands for the past 150 years, and the removal of these woodlands has been a major focus of wildlife managers and ranchers throughout the Western United States. The mechanisms driving the increase of pinyon-juniper woodlands are not well known, but may include long-term recovery from past natural disturbances, Holocene range expansion, livestock grazing, fire exclusion, and/or the effects of climatic change and rising atmospheric CO2 Tree-reduction efforts have been applied to a large amount of public lands for the last 50 years, and future tree-reduction efforts are expected to increase as managers are tasked with multiple objectives – including fire prevention and enhancing wildlife habitat in areas of increasing urbanization and energy development. With the increase in human-induced pressures on wildlife and the increase demand for more land management activities, it is imperative that we understand the effects of habitat manipulation efforts on the entire animal community that resides in the area.

We have been investigating the long-term and short-term effects of pinyon-juniper removal designed to benefit mule deer, an economically important game species in the western United States, on non-target animal communities in the Piceance Basin in Northwest Colorado. We want to know, is the best practice to remove these woodlands?  If we do, what happens to the other animals living in the forest?  How does displacing some of those other animals affect the rest of the ecosystem?

Our preliminary results suggest that the reduction of pinyon and juniper trees catalyzes a long-term change from dense pinyon-juniper forest to sagebrush scrub, consequently changing the wildlife that uses these areas. For example, woodland preferring birds like the black-throated gray warblers are rarely found in cleared sites, whereas shrubland birds like the green-tailed towhee have become common. We also found that particular wildlife groups were influenced by specific vegetative characteristics, and these characteristics could easily be maintained or created by land managers. For example, bark-gleaning birds (birds who hunt for insects up and down the trunks of trees) were more likely to use undisturbed woodlands, and tree diameter had the greatest positive influence on the probability of these birds occurring at a site. Therefore, using forest-clearing techniques that retain some large standing trees may reduce the negative impacts on bark gleaning birds.

This is just one example of how single-species management can have unintended consequences for other animals that reside in the same area. But, by understanding both the short and long-term consequences of these practices and making small changes to how we manage land, we can enhance our ability to protect and restore the biodiversity of natural communities. Given the broad and increasing impact of human activities on biodiversity, advancing our understanding of the costs and benefits of single-species management for other species of concern should be a priority for land managers and society. A large percentage of the earth’s surface has been altered through land management, and whether ecosystems can recover their natural arrangement after substantial human-disturbance remains one of the critical questions facing ecologists.

You can follow Travis Gallo and the Liba Pejchar lab on Twitter - @mellamorooster (Travis) and @thelibalab (Liba Pejchar Lab). You can also read more about Travis’ research and interests at his website.

Figure 1. The Cathedral Bluffs, Garfield County, Colorado.

Figure 2. Mule deer doe and fawns using a cleared area of pinyon-juniper forest.

Figure 3. Black-throated gray warbler (Setophaga nigrescens), a common woodland bird found in the Piceance Basin, Colorado.

Figure 4. Green-tailed towhee (Pipilo chlorurus), a common shrubland bird found in the Piceance Basin, Colorado.

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