Monday, October 1, 2012
SAGE GROUSE: PROXIMATE AND ULTIMATE CAUSES
When I was in college, one of my favorite courses was animal behavior. One of the more memorable lessons I learned was the difference between proximate and ultimate causes of behavior. Proximate and ultimate causes of events are important to distinguish.
For instance, say a researcher finds that sedimentation in streams is causing reproduction failure in trout. That is the proximate cause. Often the sedimentation is the result of logging roads—the ultimate causes. But agencies and even far too many environmental groups do not want to identify the ultimate factors causing environmental degradation because naming names is politically risky.
Worse, they often fail to connect the dots. Land management agencies tend to want to treat the symptoms, rather than confront the ultimate causes of these environmental problems. The reason for this is easy to understand from a bureaucrat’s perspective—confronting the causes for environmental degradation usually involves directly confronting some economic interest that is financially benefiting from the activity.
Livestock production and its impact on other species is one of the best examples of how ultimate causes are ignored. When we look around the West and enumerate many of the factors causing environmental concern, knowledgeable folks can easily trace the cause directly back to livestock production. For example, when streams are dried up to support irrigated hay fields, and trout/salmon populations decline due to removal of water, the proximate reason is lack of water. However, if the dewatering is used to produce hay that is fed to cattle, than the ultimate cause of aquatic ecosystem degradation is livestock production.
We see these kinds of proximate and ultimate factors with many endangered species throughout the West. Nowhere is this connection between livestock production and species decline more apparent than with sage grouse. Yet the United States Fish and Wildlife Service doesn’t even consider livestock production among the major factors in sage grouse decline.
This past week I attended the Desert Conference held in Bend, Oregon I saw yet another example of this blindness to livestock.
Among the representatives on a sage grouse discussion panel, there was a representative of the Oregon Fish and Game (ODFW). During her presentation, she commented upon the agency’s policies regarding sage grouse and she listed the threats that Oregon Department of Fish and Wildlife (ODFW) thought were a threat to the bird. ODFW identified factors like energy development, wildfire, invasive species (cheatgrass), vulnerability to predators, and climate change among the issues, nowhere was livestock grazing considered. When questioned about this seemingly inexplicable omission, she explained that ODFW thought livestock grazing benefited sage grouse.
The omission of livestock production as a major factor in sage grouse endangerment points out a serious flaw in the way agencies articulate and characterize the threats to wildlife. What the ODFW biologist did was a common error, often seen when studying natural resources issues, as well as in many other controversial topics. People often focus on the symptoms rather than the causes of observations. In this case, nearly all of the threats to sage grouse with the exception of energy development are ultimately caused by livestock production—yet the ODFW did not want to discuss, much less, mention the cow factor.
Invasive plants like cheatgrass are a problem for sage grouse, in part, because the annual cheatgrass out completes native grasses which are better hiding cover for the grouse. Cheatgrass is highly flammable and burns frequently. Due to the widespread occurrence of cheatgrass in the West, fire regimes have been altered, and we now see more frequent fires in many of our sagebrush steppe ecosystems. While the native species like sagebrush and bunchgrasses are adapted to occasional fires, they cannot survive fire year after year—a situation that often occurs when cheatgrass takes over.
Thus, as more and more cheatgrass dominates the West, there is less and less good sagebrush habitat.
But why is cheatgrass so prevalent in much of the West? The short answer is livestock. By trampling soil crusts which otherwise cover the bare spaces between native bunchgrasses, cattle often create perfect disturbed sites for cheatgrass seeds to colonize. More over cheatgrass seeds are carried from place to place on the fur of livestock, helping to ensure its widespread distribution.
Livestock also impacts sage grouse in other ways. For instance, wet meadows and riparian areas by streams are important foraging areas for sage grouse chicks during the first 3-4 weeks of life. They hunt insects in these areas and the usually dense vegetation provides cover from predators. But cattle love grazing in riparian areas and wet meadows, eliminating the cover, and often due to ”down cutting” as a result of cattle trampling of stream bank vegetation, even eliminating the wet meadows entirely.
Another factor of sage grouse mortality is fence collisions. Sage grouse are slow fliers and tend to fly only a little above the ground. As a result, they frequently run into barbed wire fences. The ODFW did not mention this as a problem, but a number of studies have shown that fences may be a major mortality factor. So the proximate cause of this mortality is collisions with fences, but again one must ask why are the fences here? They facilitate livestock production. So once again livestock is again the ultimate cause of sage grouse mortality.
Fences also impact sage grouse in yet another way. The fence posts make natural perches for birds of prey that often predate on sage grouse. So predation by a hawk or eagle maybe the proximate cause of mortality, but again livestock production is the ultimate cause of mortality. Without the fences strewn across miles and miles of sage grouse habitat, birds of prey would not be a major issue.
Another cause of sage grouse mortality is West Nile Virus. In some sage grouse populations as much as 25% of the females have died from the disease. The virus is carried by mosquitoes. so while West Nile Virus is the proximate cause of sage grouse mortality, the presence of mosquitoes is greatly enhanced by livestock stock tanks where the mosquitoes find ideal breeding habitat. So again livestock production is the ultimate cause of sage grouse mortality.
Climate change is yet another factor. Changing climate is one of the factors which includes severe drought and extended warm season are driving the fire cycles that converting many millions of acres of sage brush habitat to annual grasslands of cheatgrass and other invasive species. The reason climate is again yet another ultimate cause has to do with cattle methane releases. The bacteria in cattle rumen produce methane as a bi-product of digestion. These gases along with conversion of native vegetation to cow pastures are among the largest contributors to global warming. One World Watch paper estimates that as much as 50% of global GHG emissions may be due to livestock production.
Some opponents of sage grouse listing argue that coyotes are responsible for sage grouse decline. Never mind that coyotes and sage grouse have always co-existed, so one must ask what is the difference? The reason sage grouse are vulnerable to predators is the result of livestock removal of grasses that provide hiding cover. The proximate of sage grouse poor recruitment is coyote predation, but the vulnerability is due to the ultimate cause—livestock production.
Indeed, when considering all the mortality factors and limitations that are driving sage grouse towards extinction, livestock production is easily the dominant factor. Curiously, it was not even mentioned as a concern by ODFW, and in fact, the ODFW official said livestock grazing was considered beneficial. How can this be? The short answer appears to be that it’s politically convenient to enumerate the proximate causes rather than confront the ultimate causes for sage grouse decline. Ranchers continue to have a lot of political clout. It’s obvious that ODFW does not want to antagonize these lords of the sage.
This example of sage grouse decline and how livestock causes decline is a good lesson in proximate and ultimate causes. When you look closely at many different environmental issues in the West, one can generally trace it back to livestock production.