Widespread fencing is very detrimental to ecosystems, it could have an even more severe effect on local wildlife than just culling the wolf population. Along these same lines, this is why many eco-orgs support deer hunting (when regulated properly by state organizations); deer season is a stand-in for the natural predators that deer used to have to contend with and allows the deer population to exist without wreaking havoc on other areas of the same ecosystem that supports them.