Most areas of the National Park System are closed to hunting, a long-standing policy which is the subject of ongoing debate. A recently released study offers a scientific basis for the value of that policy to the overall health of both animal and plant species—and it includes some startling information about the impacts of humans as the "Super-Predators" in today's world.

I'd like to offer one disclaimer at the onset: I'm certainly not opposed to hunting, and properly-regulated hunting can be a useful wildlife management tool, especially in areas where natural predators have been removed from the equation.

That said, areas such as NPS sites where hunting is not allowed are valuable for many reasons, including the opportunities they provide for an increasingly urban population to readily observe a variety of wildlife species.

A new study in the Proceedings of the National Academy of Sciences provides an even more important reason to continue protecting wildlife and plants in parks from human predation: those populations may prove to be critical to the overall health or even the survival of some wild species.

Dr. Chris Darimont is a biologist at the University of California, Santa Cruz, and the lead investigator for the study,"Human Predators Outpace Other Agents of Trait Change in the Wild." Co-authors are five scientists from respected universities across North America.

The study looked at data on 29 species, including fish, invertebrates, mammals and plants. Several species studied are of particular interest in a number of parks: bighorn sheep, caribou, and American ginseng.

The study found that fishing and hunting, as currently managed, are causing surprisingly rapid changes in the body size of a variety of species, along with impacts on their ability to reproduce. The average body size of harvested populations was found to be 20 percent smaller than previous generations, and the average age of first reproduction was 25 percent earlier.

"By harvesting vast numbers and targeting large, reproductively mature individuals, human predation is quickly reshaping the wild populations that remain, leaving smaller individuals to reproduce at ever-earlier ages," said Darimont.

The rate of these changes was also startling. In animal and plant populations subject to human predation, observable changes were occurring three times faster than in natural systems.

Why is this a problem? Earlier breeders often produce far fewer offspring. Taken together, the "reduction in size and decrease in breeding age of fish and other commercially harvested species are potentially jeopardizing the ability of entire populations to recover."

"The pace of changes we're seeing supercedes by a long shot what we've observed in natural systems, and even in systems that have been rapidly modified by humans in other ways," Darimont noted. "As predators, humans are a dominant evolutionary force…Harvested organisms are the fastest-changing organisms of their kind in the wild, likely because we take such high proportions of a population and target the largest. It's an ideal recipe for rapid trait change."

So, what does this have to do with restrictions on hunting in most NPS areas?

I asked Dr. Darimont to comment on the idea that protected areas such as national parks can serve as reservoirs of genetic vigor and diversity for wild animals and plants, since other than losses due to poaching, the larger and older individuals are more likely to live and reproduce longer in those areas. He responded:

"Yes, protected areas, both marine and terrestrial, can safeguard fishes and mammals from potential evolutionary influences of human predation. The trick is to have them large enough to adequately protect mobile species that cannot recognize the boundaries of smaller parks or no-catch areas."

What about areas—in parks and elsewhere—where sport and subsistence hunting is allowed? You don't see many photos of proud hunters with spike bucks in hunting magazines, and conventional wisdom has been that removal of trophy-quality individuals from a population is not a problem.

This research offers a different opinion that's bound to generate some controversy—and keep in mind that the research findings deal not only with hunting, but also fishing:

"Ironically, some wildlife and fish management policies contribute to the rapid pace of trait changes. "Fishing regulations often prescribe the taking of larger fish, and the same often applies to hunting regulations," said Darimont. "Hunters are instructed not to take smaller animals or those with smaller horns. This is counter to patterns of natural predation, and now we're seeing the consequences of this management." In Alberta, Canada, for example, hunters who are permitted to target the largest specimens of bighorn sheep have caused average horn length and body mass to drop by about 20 percent during the last 30 years.

Even more startling than the reduction in size is the unexpectedly rapid rate of change in these individuals.

"The public knows we often harvest far too many fish, but the threat goes above and beyond numbers," said Darimont. "We're changing the very essence of what remains, sometimes within the span of only two decades. We are the planet's super-predator."

The findings aren't limited to animals. Dr. Paul Paquet is a biologist at the University of Calgary, and another scientist participating in the study. He notes that as ginseng is harvested in the wild, "the robustness and size of the plant is declining." Ginseng poaching has been a long-standing problem in some parks, and this study supports the need to continue efforts to control poaching in protected areas.

While subsistence poachers of wildlife are less selective when looking for meat for the freezer, those mature elk and bighorn sheep with the prized racks are prime targets for other illegal hunters. Based on this research, the impact of such trophy selection may be greater than previously believed.

There are other implications for NPS managers.

A number of parks are wrestling with how to deal with an overpopulation of deer or elk. Where that's the case, there's plenty of debate about how to reduce those numbers—and who should do the work. Should the area be opened to public hunting, or should reductions be accomplished in a more controlled manner using pre-screened and presumably better qualified hunters? Would the best results be achieved using park or other government personnel?

That debate about the "who" goes on, but if it's deemed necessary to reduce wildlife populations in some parks, this study confirms the need for careful controls on not only how many, but perhaps even more important, which animals are taken. "This should be a wake-up call for resource managers," Darimont said. "We should be mimicking natural predators, which take far less and target smaller individuals."

I asked Dr. Darimont for his opinion about managed wildlife reduction programs. He replied,

"As a general rule, we'd expect less evolutionary impact if hunting and fishing mimics natural predation. This means forgoing our typical preference for the largest and taking far fewer individuals from a population each year. But in the context of parks, instead of control efforts, I would strongly favor restoration of natural predators like wolves over lethal control by park managers."

Not all areas are good candidates for reintroduction of predators, but the findings of this research deserve careful consideration as part of the planning for any reduction programs. It will be very interesting to watch the reaction of the wildlife management and hunting and fishing communities to this study, because it clearly calls for a reexamination of some well-entrenched practices.

There's also a significant political dimension to potential changes in hunting and fishing guidelines. In parks where hunting or fishing is allowed, regulations are usually under the control of state agencies, not the NPS. There's a lot at stake in financial as well as biological terms, and if this research receives the attention it deserves, expect some monumental political battles in the years ahead.

As a minimum, this information confirms the value of continuing to protect some animal and plant populations that are as free of human interference as possible. Those populations may prove to be invaluable—and irreplaceable—reservoirs of genetic diversity and vigor.

National parks have long been valued by many as places of "wildness" (as distinguished from "wilderness.") Henry D. Thoreau's quote, "In Wildness is the preservation of the world” is a popular one with advocates of preserving natural areas for their intrinsic values. This new study of human impacts on both plant and animal populations suggests that in recognizing the values of "wildness," Thoreau seems to have been on to something.