Conservation Northwest protects and connects old-growth forests and other wild areas from the Washington Coast to the British Columbia Rockies, vital to a healthy future for us, our children, and wildlife. Since 1989, Conservation Northwest has worke
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Getting wilder The Trickle Down W hen God told Noah to load the Ark, he didn't tell the Biblical sailor to maroon the predators. Even back in the day, gods and men alike understood the need for balance in all things. So the lions, tigers, bears, and wolves all got to go sailing. So what does "balance" mean on the dirt of the everyday ecological playing field? It is where complex interactions unfold between predator and prey, a shared balance that affects in ways not often apparent the myriad other species that share the neighborhood. From the ecological perspective, balance is defined by the dozens of species interactions driven by struggles between predator and prey under the ground rules of natural selection. This is the second installment in a two-part series on predators and prey. The first part ran in our spring/summer Conservation Northwest Quarterly. Grizzly bear and salmon in Kenai, Alaska. © Chris Weston, chrisweston.uk.com For the wolf and elk, cheetah and gazelle, orca and salmon the dynamic is clear: Eat and be eaten, adapt or die. But it doesn't stop there. The effects of those interactions ripple out across the landscape and the ecological communities, much like local economies. How the ecological economy stays afloat Consider what happens when you patronize a local restaurant, like Pascuale's local Torre Café, rather than a big chain store. At Pascuale's, in return for stories about the Genoan countryside and a rhapsody on the simplicity of sardines and spaghetti, you get to help diversify the local Bellingham economy. People congregate in a part of town that wouldn't see such social interactions without the cafe. It becomes a more interesting and lively neighborhood, in turn making Bellingham a more diverse and vibrant town. By patronizing a mom-and-pop shop like Pascuale's you help prevent what ecologists call "competitive exclusion," a dynamic whereby the "stronger" organisms outcompete the "weaker" ones. By exercising your spending choices you are in effect erecting economic boundaries that are protecting the little fish from the big ones. 4 Fall 2011 Now, consider how predators benefit your ecological neighborhood. Apex predators, like bears, wolves, tigers, and lions are purveyors of biological diversity that operate similarly to human consumers. By preying on certain species, predators, biologists believe, can help level the ecological playing field, by limiting more dominant prey species, both numerically and behaviorally. This winnowing allows others to survive, which in turn makes for more diverse, complex, and resilient ecosystems. For example, there is data to suggest that mule deer are at a competitive disadvantage to elk and white-tailed deer for the most productive habitats where these animals' ranges overlap. Since wolves prefer elk for dinner—because elk are the best "Full Meal Deal" in the West—the predator keeps the prey offbalance and on the go, essentially allowing for a redistribution of ecosystem wealth to the slight advantage of the mule deer. By limiting the populations of grazers and browsers generally, carnivores ensure that overall ecosystem production remains robust, which in turn creates habitat for a wide variety of creatures, from birds to spiders. Removing the top predators dissolves the ecological boundaries and may cause one prey species to out-compete another for scarce resources, thus compromising the weaker one's ability to survive. www.conservationnw.org