The future of wolves in GYE will depend on how livestock depredation and hunting of wolves outside the park are handled. Wolf populations will also continue to be affected by the availability of elk, deer, and bison, which fluctuates in response to hunting quotas, winter severity, and disease. To what extent wolves may have contributed to the decline in the northern Yellowstone elk population since the mid- 1990s, or the possibly related resurgence of willow in some areas, is an ongoing topic of debate.