A beautiful animal that also happens to arguably be the
greatest threat to forests in the eastern United States. Photo: Matt
Miller/TNC
By Allen Pursell, Southern Indiana Program Director, The Nature
Conservancy in Indiana; Troy Weldy, Director of Ecological Management, The
Nature Conservancy in New York; Mark White, Forest Ecologist, The Nature
Conservancy in Minnesota and the Dakotas
“I now suspect that just as a deer herd
lives in mortal fear of its wolves, so does a mountain live in mortal fear of
its deer.” —Aldo Leopold, A Sand County Almanac, 1949
In August, 2012 The Bloomberg View published a staff editorial entitled
Deer
Infestation Calls for Radical Free-Market Solution. The
Wall Street
Journal then ran a story in November 2012 entitled
America
Gone Wild, noting the impact of overabundant deer.
If business news
organizations can talk freely about deer, The Nature Conservancy (TNC) needs
to speak openly as well. Aldo Leopold long ago warned us of the problems of a
growing deer herd. Have we waited too long to heed his advice, or is there still
time to reverse the damage done?
No native vertebrate species in the eastern United States has a more
direct effect on habitat integrity than the white-tailed deer. There are no
hard numbers, but in many states deer populations continue to rise well beyond
historical norms. In many areas of the country deer have changed the composition
and structure of forests by preferentially feeding on select plant species.
In northern Minnesota, TNC staff demonstrated that decades of overbrowsing
led to recruitment failure for many tree species, a shift in subcanopy and
canopy dominance towards non-preferred white spruce, and significantly lower
forest productivity (White 2012). In New York, TNC scientists report that
one-third of New York’s forests are currently compromised as a result of
excessive herbivory (see
New York
Forest Regeneration Study).
Findings similar to these have been documented across the country. U.S.
Forest Service researchers have noted that even if areas with high deer
densities were managed to reduce the impact of deer, there may be long-lasting
legacy effects (Royo 2010). Webster (2005) found severe and lasting impacts at
Smoky Mountain National Park to be so complete that some plants such as
trilliums were unlikely to recolonize local areas on their own. Deer are also
well-documented vectors for the dispersal of non-native exotic plants (Knight et
al. 2009, Baiser et al. 2008, Williams and Ward 2006).
Indirect effects on wildlife have been reported as well, such as
widespread declines of North American songbird populations (Chollet
2012). One study found forest songbirds that preferred nesting in the shrub and
intermediate canopy layer declined in abundance and species richness as deer
density increased (deCalesta 1994).
White-tailed deer likely impact every landscape east of the Mississippi
River. The damage has been insidious — both slow moving and cumulative.
Unfortunately, the harm is often overlooked, or worse, accepted as somehow
“natural.”
In our opinion, no other threat to forested habitats is greater at this
point in time — not lack of fire, not habitat conversion, not climate
change. Only invasive exotic insects and disease have been comparable in
magnitude. We can argue about which threat is more significant than another, but
no one who walks the eastern forests today can deny the impact of deer to forest
condition.
It is clearly true that fire suppression has had a widespread impact on
successional trajectory and tree species composition. A natural fire return
interval would be a great benefit to many eastern forests. Yet even where fire
is present, excessive deer herbivory has been shown to depress tree species
diversity or at least minimize the benefits of fire. In the words of a recent
study on the interactions of fire, canopy gaps, and deer browsing: “… restoring
disturbances without controlling browsing may be counterproductive.” (Nuttle,
2013)
While we acknowledge that climate change is a long-term stressor that will
lead to significant changes in eastern forest ecosystems,
high deer
populations have had a much greater negative impact currently and over the
last several decades. At present there is little evidence of direct climate
change impacts on eastern forests (Beckage et al. 2008, Woodall et al. 2009, Zhu
et al. 2012, Rustad et al. 2012). With climate envelope and other modeling
systems, we have a general understanding about likely range shifts and
compositional changes in eastern forests over the next 50-100 years. However,
due to the many interacting factors such as atmospheric deposition (nitrogen,
ozone), insect pests and pathogens, invasive plants, CO
2 enrichment,
longer growing seasons, and white-tailed deer populations, there is a high
degree of uncertainty about the future condition and function of eastern forests
in a changing climate (Frelich and Reich 2009, Rustad et al. 2013).
No such uncertainty exists regarding the negative impacts of high deer
populations on eastern forests; the body of evidence is unequivocal. In this
article, we present only a small fraction of the literature on deer impacts.
Reducing the impact of deer herbivory is currently a key forest restoration
strategy (White 2012, Nuttle et al. 2013) and likely will become more important
in order to help maintain resilient, functioning forests in a warming climate
(Galatowitsch et al.2009).
Engaging society to address the problem will be difficult, probably similar
to our experience with wild pig eradication in California and Hawaii, but on a
wider scale.
Views on deer management are deeply entrenched, both among
those who hunt and those who don’t. People have strong opinions when it comes to
deer.
A Call to Action
The forest understory is nearly absent except for
Japanese stiltgrass. Note the deer appears to be especially thin. Valley Forge
National Historical Park, Pennsylvania. Photo: Ron Rathfon.
Change is possible but it won’t be easy or quick.
Deer management cannot be regulated at the federal level. As early as
1896 the Supreme Court ruled that states have “ownership” of their wildlife. As
a result, each state has its own intricate rules. State regulations need not be
standardized, but efforts at reform must be made state-by-state. This process
will be slow as rules are generally promulgated by processes that ensure
adequate evaluation by respective wildlife authorities and to allow for public
review.
Nevertheless, some states are beginning to do the difficult work of changing
policies to stabilize or reduce the number of deer. For example, Indiana
recently enacted the first modern firearms season targeting female deer in the
state’s history.
It will be
difficult to overcome traditional hunter concepts of proper
deer management as it is counter-intuitive to most hunters that fewer game
animals are desirable. Decades of effort, patience, and expense were invested to
enhance populations to the point where hunting success is now commonplace. To
suggest that populations be reduced and therefore increase the effort needed to
harvest a deer understandably generates resistance. Success will take a
carefully crafted and sustained public relations effort.
Like almost all conservation problems,
deer management is a societal
issue. If the deer population is to be reduced, it must be reduced slowly.
Rules that lower the population drastically will almost certainly spur a
backlash from hunters who can appeal to their respective legislatures to
overturn regulations they regard as harsh. In an effort to lower the population
of deer in Wisconsin the DNR liberalized hunting dramatically.
The result was a hunter revolt. Gov. Scott Walker campaigned on a
pledge to fix deer management. Once elected, he made good on that promise by
appointing a deer trustee to evaluate his state’s DNR. The trustee’s final
report noted that by failing to adequately communicate with hunters and involve
them in determining solutions the DNR had lost credibility (Kroll 2012). A
similar push back may be occurring in Pennsylvania.
In some sense
one of the greatest losses of all is that deer are no
longer viewed as the majestic and even mystical animals of the forest that they
were only a few decades ago. To quote Bloomberg: “… it’s hard to think of a more
insidious threat to forests, farms and wildlife, not to mention human health and
safety, than deer.”
How different that is from the time of John Muir, who wrote,
“Standing, lying down, walking, feeding, running even for its life, it [deer] is
always invincibly graceful, and adds beauty and animation to every landscape — a
charming animal and a great credit to nature.”
Opinions expressed on Cool Green Science and in any corresponding
comments are the personal opinions of the original authors and do not
necessarily reflect the views of The Nature Conservancy.
References
Allan B.F., L.S. Goessling, G.A. Storch, and R.E. Thach. 2010. Blood meal
analysis to identify reservoir hosts for Amblyomma americanum ticks.
Emerging
Infectious Disease 16(3):433-440.
Baiser, B.J., L. Lockwood, D. La Puma, and M.F.J. Aronson. 2008. A perfect
storm: two ecosystem engineers interact to degrade deciduous forests of New
Jersey.
Biological Invasions 10: 785-795.(Beckage, Osborne et al.
2008)
Beckage, B., B. Osborne, et al. 2008. A rapid upward shift of a forest
ecotone during 40 years of warming in the Green Mountains of Vermont.
Proc
Natl Acad Sci USA 105: 4197-4202.
Beckage, B., B. Osborne, D.G. Gavin, C. Pucko, T. Siccama and T. Perkins
2008). “A rapid upward shift of a forest ecotone during 40 years of warming in
the Green Mountains of Vermont.”
Proc Natl Acad Sci USA 105(11):
4197-4202.
Bloomberg View. (2012, August 8). Deer infestation calls for Radical
Free-Market Solution. Bloomberg.com. Retrieved January 18, 2013 from
http://www.bloomberg.com/.
Chollet, S. and J. Martin. 2012. Declining woodland birds in North America:
should we blame Bambi?
Diversity and Distributions doi:
10.1111/ddi.12003.
Conover, M.R. 1998. Perceptions of American agricultural producers about
wildlife on their farms and ranches.
Wildlife Society Bulletin
26(3):597-604.
deCalesta, D.S. 1994. Effect of white-tailed deer on songbirds within managed
forests in Pennsylvania.
Journal of Wildlife Management 58(4):
711-718.
Fagerstone, K.A. and W. H. Clay. 1997. Overview of USDA Animal Damage Control
Efforts to Manage Overabundant Deer.
Wildlife Society Bulletin 25(2):
413-417.
Frelich, L.E. and P.B. Reich. 2010. Will environmental changes reinforce the
impact of global warming on the prairie–forest border of central North America?
Frontiers in Ecology and the Environment 8: 371-378.
Galatowitsch, S., L. Frelich. 2009. Regional climate change adaptation
strategies for biodiversity conservation in a midcontinental region of North
America.
Biological Conservation 142: 2012-2022.
Knight, T.M., J.L. Dunn, L.A. Smith, J. Davis, and S. Kalisz. 2009. Deer
facilitate invasive plant success in Pennsylvania forest understory.
Natural
Areas Journal 29(2): 110-116.
Kroll, J.C., D.C. Guynn, Jr, and G.L. Alt. 2012. Final Report and
Recommendations by Wisconsin White-tailed Deer Trustee and Review Committee.
2012. Madison, Wisconsin. 136 pp.
Nuttle, T., A.A. Royo, M.B. Adams, and W.P. Carson. 2013. Historic
disturbance regimes promote tree diversity only under low browsing regimes in
eastern deciduous forest.
Ecological Monographs 83(1): 3-17.
Royo, A.A., S.L. Stout, D.S. deCalesta, T.G. Pierson. 2010. Restoring forest
herb communities through landscape-level deer herd reductions: Is recovery
limited by legacy effects?
Biological Conservation 143: 2425-2434.
Rustad, L., J. Campbell, J. Dukes, T. Huntington, K. Fallon Lambert, J.
Mohan, N. Rodenhouse. 2012. Changing Climate, Changing Forests: The Impacts of
Climate Change on Forests of the Northeastern United States and Eastern Canada.
USDA Forest Service, Northern Research Station General Technical Report NRS-99:
56pp.
State Farm Mutual Automobile Insurance Co. (2012, October 23). It’s West
Virginia Again. Mountain State Leads State Farm’s List of States Where
Deer-Vehicle Confrontations Are Most Likely. Statefarm.com. Retrieved January
18, 2013 from
http://www.statefarm.com/.
Wall Street Journal. (2012, November 2). America Gone Wild.
online.wsj.online.com. Retrieved January 18, 2013 from
http://online.wsj.com/.
Webster, C.R., M.A. Jenkins, J.H. Rock. 2005. Long-term response of spring
flora to chronic herbivory and deer exclusion in Great Smoky Mountains National
Park, USA.
Biological Conservation 125: 297–307.
White, M.A. 2012. Long-term effects of deer browsing: Composition, structure,
and productivity in a northeastern Minnesota old-growth forest.
Forest
Ecology and Management 269:222-228.
Williams, S.C. and J.S. Ward. 2006. Exotic seed dispersal by white-tailed
deer in southern Connecticut.
Natural Areas Journal 26(4): 383-390.
Woodall, C.W., C.M. Oswalt, J.A. Westfall, C.H. Perry, and A.O. Finley.
2009. An indicator of tree migration in the eastern United States.
Forest
Ecology and Management 257: 1434-1444.
Zhu, K., C.W. Woodall and J.S. Clark. 2012. Failure to migrate: lack of tree
range expansion in response to climate change.
Global Change Biology 18:
1042-1052.
Allen Pursell has been with The Nature Conservancy in
Indiana for 19 years and holds a BS and MS in Forestry from Purdue University.
Contrary to what the article may lead you to believe he likes deer very much.
Mark White is the Forest Ecologist for The Nature Conservancy in Minnesota and
the Dakotas. Mark’s work focuses on ecological forestry, habitat conservation,
and climate change adaptation. Troy Weldy is Director of Ecological Management
for The Nature Conservancy in New York.
|