June 13, 2012

Carnivores’ give and take

This is an editorial on the Rewilding Institute‘s web site by Dave Parsons:

What’s the big deal about carnivores?

A large body of literature supports the conclusion that large carnivores are critical components of healthy and biologically diverse ecosystems.  Large carnivores tend to promote plant and animal diversity and ecosystem complexity.

Their removal can unleash a cascade of effects and changes throughout all ecosystem trophic levels reducing biological diversity, simplifying ecosystem structure and function, and interfering with ecological processes.  Their return to impoverished ecosystems can reverse the cascade and restore diversity and complexity to ecosystems.

We are witnessing such ecological rebirth in Yellowstone National Park following the return of the wolf to that ecosystem.  Riparian willows and cottonwoods are returning because elk spend more time moving and hiding to avoid becoming wolf scat.  With their table reset, beavers are returning to the streams.

These “ecological engineers” provide homes for myriad critters from aquatic insects to fish to songbirds.  The extent of changes is certainly far more complex than we can observe or document.

The critical role of carnivores kicks in when viable populations are allowed to persist at ecologically effective population densities over large areas—really large areas.

“Areas apparently needed to maintain viable populations [of large carnivores] over centuries are so large as to strain credibility; they certainly strain political acceptance.”  Noss et al. (1996:950)