At least 27 species of native mammal once inhabited the Roxby Downs region but over 60% have become locally or completely extinct since European settlement. Some bird species such as the Bush Thick-knee and Plains Wanderer have also become locally extinct or endangered.
The main reasons for the decline of the local native fauna and flora are overgrazing by rabbits and domestic stock, and predation from introduced animals like the feral cat and fox. Medium-sized desert mammals have been most affected with many now globally extinct or have disappeared from mainland Australia and survive only on off-shore islands.
Since the inception of grazing in arid rangelands, there have been extensive vegetation changes. Many parts of arid Australia were severely over-grazed by sheep and cattle during the advent of pastoralism in the 19th Century. Overgrazing by domestic stock and rabbits has a significant effect on arid zone vegetation; long-lived arid zone trees and shrubs are prevented from regenerating, and long-lived plant species are being replaced by short-lived annual and weed species. Whilst current pastoral practices are much more conservative there are still many areas degraded by pastoralism.