Livestock are one of the major factors in the spread of exotic weeds. The soil disturbance caused by hooves and trampling has created ideal colonization habitat for weeds. Plus the continued grazing of desirable native species weakens their ability to complete with exotics for water, space and food. Cattle also often assist in the spread of weeds by carrying seeds in their fur or excreting them with their manure. Livestock consumption of grass and other fine fuels has altered natural fire regimes and by eliminating or weakening grass plants, has given trees and shrubs a competitive advantage that has led to overstocked forests and shrub invasion of former grasslands.
Livestock are the number cause of riparian degradation in the West.
Riparian areas are the thin green lines of water dependent vegetation found along waterways. The decline in riparian habitat quality has severely impacted many of the West's wildlife species. Livestock directly complete with native species for forage. Every blade of grass going into a cow is that much less available for native species from grasshoppers to grizzlies. But the effects can be less obvious than this.