Pre-Settlement Forest - 1700 A.D., Harvard Forest

Even-aged forest with severe white-tailed deer browse

This article about overabundant elk (additional link here) and discussion about re-introduction of wolves on the Olympic Peninsula is fascinating.   It made me recall how the current overabundance of large herbivores is ecologically novel.  

Our native herbivores evolved with predators, thus primeval plant communities evolved to predator/prey dynamics that didn’t have human influence.  When you remove this predator/prey dynamic, herbivores change behavior, their populations increase, and plant communities change.  Certain plants are more resistant to being browsed, while others are extremely sensitive.  This observation is nothing new, in fact, Aldo Leopold pointed this more than half a century ago critizing wholesale predator reduction as a wildlife management technique.  Here is a very rough, admittedly oversimplified time line:

• 40,000 years ago – 1500′s, Native Americans inhabited this Continent and had an impact on herbivore populations, potentially driving some to extinction, and purposely increasing populations of others.  They also had an impact on herbivore populations by reducing predators.  
• 1500′s – 1880′s, Europeans settled North America, agrarian society continued subsistence hunting of wild herbivores and hunted many native herbivores to local extirpation.  At the same time, European settlers eliminated predators.
• 1880′s – 1940′s,  Urbanization of North America, market hunting drastically lowers populations of large herbivores, scientific wildlife management begins as a reaction to loss of large herbivores, wide-scale elimination of predators continues, and re-introduction of extirpated herbivores is carried out, subsistence hunting transforms to recreational hunting.  
• 1940′s – today  Suburbanizaion,  As scientific management of wildlife became wildly successful at restoring extirpated herbivore populations, the underlying landscape changes and we become a more suburban society.  

Without a doubt, highly regulated recreational hunting can increase herbivore populations, but we have not proven that recreational hunting can control herbivore populations the way predators, native Americans, or subsistence colonials did.  Currently, we don’t have the ability to reduce herbivore populations down to what my professor Oz Schmitz  would call “ecological carrying capacity.” 

I can understand how ecological carrying capacity is a bit of a fluffy concept to some, but clearly here in New Jersey we are far from attaining it.  Examples abound.  In the Pinelands, we can’t figure out how to regenerate an Atlantic white cedar forest or sustain populations of rare plants without excluding white-tailed deer.  In the Highlands, traditional sivlicultural practices designed to regenerate forests also don’t work without fencing.  We clearly have herbivore populations that are above ecological carrying capacity.

Wildlife management originally focused on large herbivores and developed as a  reaction to the problem of local, severe decline and often extirpation of local populations.  This underabundance drove the choices and ethic in wildlife management and has lead to it being overly successful at bringing back native herbivores.  

Wildlife management agencies have failed to adapt to overabundance for a few reasons. The economic incentives for wildlife management agencies were and still are tied to this underabundance.  Wildlife agencies are funded by hunting licences, so the better (and easier) the hunting, the more licences they sell and the more revenue they receive.  This leads to agencies managing populations to overabundance.   Furthermore, they have failed to adapt management techniques to the suburbanization of the landscape.  In New Jersey, the edge habitat created by suburbia provides ideal habitat for white-tailed deer and is responsible for increased populations.  

Wildlife management of large herbivores has been too successful at increasing populations and is leading to degradation of ecosystems in New Jersey and across the continent.  We need to adopt a different wildlife management ethic focused not on underabundance but rather on ecological carrying capacity.  We also need to change the economic incentives that drive wildlife agencies.  Only then can we develop effective tools to deal with one of the biggest threats to our natural lands.

I’ll elaborate on theses ideas over the next several months…