The journal Bioscience (October 2009) recently published "The Rise of the Mesopredator" [PDF]. Science Codex covers the researchers' coclusions:

"In case after case around the world, the researchers said, primary predators such as wolves, lions or sharks have been dramatically reduced if not eliminated, usually on purpose and sometimes by forces such as habitat disruption, hunting or fishing. Many times this has been viewed positively by humans, fearful of personal attack, loss of livestock or other concerns. But the new picture that's emerging is a range of problems, including ecosystem and economic disruption that may dwarf any problems presented by the original primary predators.... "The economic impacts of mesopredators should be expected to exceed those of apex predators in any scenario in which mesopredators contribute to the same or to new conflict with humans," the researchers wrote in their report. "Mesopredators occur at higher densities than apex predators and exhibit greater resiliency to control efforts." The problems are not confined to terrestrial ecosystems...."

Interesting article. Hopefully, it will lead to smarter interactions with nature. We're the apex species, which means stewardship whether we like or not. Might as well get good at it.

One wonders, too, if there may be some applications to human predators, as well.