Impacts Of The Wild Horses
Before the introduction of domesticated farm animals, much of eastern Washinton was covered with large sagebrush and several species of perennial grass.
This environment proved ideal for the horses introduced into the area prior to the westward migration of American and European immigrants
Soon after immigrants arrived with herds of cattle, sheep and domestic horses, severe overgrazing of this delicate ecosystem began.
Yakima newspapers were discussing problems associated with overgrazing, both on and off the reservation, as early as in the 1890s.
The new arrivals also introduced a highly invasive annual grass, called Cheatgrass, which, unlike the native grasses, produced seeds that can germinate and grow during the winter, even under snow. Consequently, Cheatgrass quickly replaced many of the perennial grasses throughout much of the arid west.
Cheatgrass produces lush green growth early in spring, but in early summer, the plant produces seeds, matures and dies.
From late summer through winter only dry stems remain as the primary forage for grazing animals.
This scarcity of nutritious forage for 3-4 months each year. combined with a dramatic increase in the horse population over a period of two decades during the early 2000s created many environmental problems on parts of the Reservation, some of which persist.
Trails
When horses graze, they spread out and eat as they move. They leave few tracks as they go.
But, when they travel to and from water they often move in columns of one or two animals.
As a result, over time, they produce very distinct trails, especially between their watering holes and their preferred grazing sites.
On hillsides, there is a difference in trails made by cows and horses.Cattle trails tend to angle across the face of gentle slopes.
Horses tend to move mostly straight up steep hillsides. This is a screen capture from Google Earth that shows a network of trails leading up steep cliffs from watering holes on Dry Creek.
On the plateaus above the creeks, complicated trail networks continue through areas of sagebrush to their preferred grazing sites.
Not only do the trails compact the soil but they also accelerate erosion of the land by forming conduits for runoff water. In some areas eroded trails can be 4-5 feet deep.
Damage to Springs and Streams
As the horse population increased over the years, foot traffic at the water sources increased substantially, creating many physical damages.
The ground around springs is usually baren and packed hard by the horse’s hooves. Water is frequently contaminated by mud and feces.
Trails often extend into the water where horses disturb the loose soil which, in turn, severely impacts salmon spawning beds.
Lithosols
Lithosols are areas of shallow soil covered with partially weathered rocks, often on hillsides.
In spring, these areas are covered with many species of wildflowers and a species of sagebrush called little sagebrush.
By midsummer, horses have consumed all the annual plants including the Cheatgrass.
By late fall they have browsed all the limbs from the little sagebrush plants until nothing but stems remain.
Preferred Feeding Site
There are certain areas on the Reservation where wild horses seem to graze even after all the vegetation is gone.
The high density of horses in these areas over prolonged periods results in highly compacted soils with high urine concentrations.
This combination ultimately kills any remaining plants including the big sagebrush.
These are only some of the visual impacts of high wild horse population. Unphotographed impacts include the disappearance of many of the animal species that are integral parts of the shrub-steppe ecosystem.
What is needed?
Tests show that many of the impacts discussed here can be reduced or eliminated by excluding horses for a few years.
The question now, as it has been for the past two decades, is how can wildlife biologists reduce the number of horses to sustainable levels in ways that are acceptable with Yakama culture.
While horse numbers are lower now than they were a decade ago when many of the photos were taken, they are nowhere near the 1000 animals projected as sustainable in the 2007 project report.
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