A prized specimen for hunters, but how does removing the biggest and best affect the long-term health of the herd?
Photo by bmass via Flickr.
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.
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