Environmental Problems, Their Causes, and Sustainability 1

11 ManagingSustaining Terrestrial Biodiversity:and Protecting EcosystemsBiodiversityCASE STUDYReintroducing Wolvesto YellowstoneFigure 11-1 The gray wolf is a threatenedspecies in the lower 48 states. Ranchers,hunters, miners, and loggers have vigorouslyopposed efforts to return this keystonespecies to its former habitat in the YellowstoneNational Park area. However, wolveswere reintroduced beginning in 1995 andnow number several hundred.At one time the gray wolf (Figure 11-1) ranged overmost of North America. But between 1850 and 1900 anestimated 2 million wolves were shot, trapped, andpoisoned by ranchers, hunters, andgovernment employees. The idea wasto make the West and the Great Plainssafe for livestock and for big game animalsprized by hunters.It worked. When Congresspassed the U.S. Endangered SpeciesAct in 1973, only about 400–500 graywolves remained in the lower 48states, primarily in Minnesota andMichigan. In 1974 the U.S. Fish andWildlife Service (USFWS) listed thegray wolf as endangered in all 48lower states except Minnesota. Alaskawas also not included because it had6,000–8,000 gray wolves.Ecologists recognize the importantrole this keystone predatorspecies once played in parts of theWest and the Great Plains. Thesewolves culled herds of bison, elk, caribou,and mule deer, and kept downcoyote populations. They also provideduneaten meat for scavengerssuch as ravens, bald eagles, bears,ermines, and foxes.In recent years, herds of elk,moose, and antelope have expanded.Their larger numbers have devastatedsome vegetation, increased erosion, and threatenedthe niches of other wildlife species. Reintroducing akeystone species such as the gray wolf into a terrestrialecosystem is one way to help sustain its biodiversityand prevent environmental degradation.In 1987, the USFWS proposed reintroducing graywolves into the Yellowstone ecosystem. This broughtangry protests. Some objections came from rancherswho feared the wolves would attack their cattle andsheep; one enraged rancher said that it was “like reintroducingsmallpox.” Other protests came fromhunters who feared the wolves would kill too manybig game animals, and from mining and logging companieswho worried the government would halt theiroperations on wolf-populated federal lands.Since 1995, federal wildlife officials have caughtgray wolves in Canada and relocated them in YellowstoneNational Park and northern Idaho. By 2004 therewere about 760 gray wolves in thesetwo areas.Their presence is causing a cascadeof ecological changes in Yellowstone.With wolves around, elk aregathering less near streams andrivers. This has spurred the growthof aspen and willow trees that attractbeavers, and elk killed by wolvesare an important food source forgrizzlies.The wolves have cut coyotepopulations in half. This has increasedpopulations of smaller animalssuch as ground squirrels andfoxes hunted by coyotes, providingmore food for eagles and hawks. Between1995 and 2002 the wolves alsokilled 792 sheep, 278 cattle, and 62dogs in the Northern Rockies.In 2003, the U.S. Fish andWildlife Service downgraded thegray wolf throughout most of thelower 48 states from endangered tothreatened. In 2004, the agency proposedremoving wolves from protectionunder the Endangered SpeciesAct in Idaho and Montana. Thiswould allow private citizens in thesestates to kill wolves that are attacking livestock orpets on private lands. Conservationists say this actionis premature, warning that it could undermine one ofthe nation’s most successful conservation efforts.Population growth, economic development, andpoverty are exerting increasing pressure on theworld’s forests, grasslands, parks, wilderness, andother terrestrial storehouses of biodiversity. This chapterand the two that follow are devoted to helping usunderstand and sustain the earth’s biodiversity.