Is Carrboro an “Area With Deer Overpopulation”?

This is the second in our series analyzing Carrboro’s Energy and Climate Protection Task Force’s Recommended Deer Cull.

Assertion 2: “Soil studies have shown that the seed stores in areas with deer overpopulation are shifting from native wildflowers and woody plants to invasive plants and grasses. This threatens the ability of our forests to regenerate in a healthy way and continue to serve as diverse ecosystems and significant carbon sinks.” [page 38]

Again, although there are three end notes at the bottom of page 38, none of them references any studies regarding deer and their adverse affect on seed stores or forest regeneration.

The first problem with this assertion is that it starts with a claim about “deer overpopulation” without defining what deer overpopulation is, and without any proof that deer overpopulation is a problem in Carrboro.

So, does Carrboro have a problem with deer overpopulation?

Biologically speaking, overpopulation of a particular species occurs when that species exceeds its biological carrying capacity, or the maximum number of individuals of a species that can exist in a given habitat indefinitely. Factors that affect carrying capacity include the availability of life-sustaining necessities (such as food, water, and cover) and life-threatening situations (such as predators, toxins, and disease).

Deer and other large wild animals rarely exceed their biological carrying capacity. If there is not enough food available to support the population, the weaker individuals will die and the does will absorb some embryos and fewer fawns will be born in the spring.

Is that the situation in Carrboro? No. There is at least one doe in Carrboro who has been crippled since she was very young, either from a pre-natal injury or post-natal injury. This year, that crippled doe delivered and raised a healthy fawn. At least one other doe in Carrboro delivered and raised healthy triplets this year. These are not the signs of overpopulation. These are the signs of a deer population living well within the carrying capacity of the local environment.

What is the biological carrying capacity for deer in urban areas? According to urban wildlife specialist Ricky Lien, “The biological carrying capacity of many of our urban areas can be over 100 deer per square mile.”

The second problem with this assertion is that the deer “overpopulation” causes the spread of invasive species. Yet elsewhere in the Community Climate Action Plan, there is a reference to one of the challenges of the spread of invasive plant species: “Large/big box nurseries often sell few (if any) native species.” Surely, the authors of the plan realize that humans, not deer, are making the purchasing and planting decisions that are the major reason for the spread of invasive species.

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Do “Excess Deer” Adversely Affect the Health of Our Forests by Causing a Decrease in Plant Diversity and Aiding in the Spread of Exotic Species?

This is the first in our series analyzing Carrboro’s Energy and Climate Protection Task Force’s Recommended Deer Cull.

Assertion 1: “Local and other studies have shown that excess deer are adversely affecting the health of our forests by causing a decrease in plant diversity and aiding in the spread of exotic species.” [page 38]

Although there are three end notes at the bottom of page 38, none of them references any studies regarding deer and their adverse affect on the health of forests.

So are “excess deer” (whatever that means) the primary cause of decreasing plant diversity and spreading of exotic species?

According to a review in the journal Science, no. “For terrestrial ecosystems, land-use change probably will have the largest effect, followed by climate change, nitrogen deposition, biotic exchange, and elevated carbon dioxide concentration.” In other words, humans are the primary cause of a decrease in plant diversity and the spreading of exotic species.

There are some good articles on the effects of deer on forest regeneration here. This study, in particular, found that “adult trees inside exclosures grew less than those directly exposed to deer. Our findings highlight the indirect effects of white-tailed deer on the growth of adult individuals of Q. rubra in a way opposite of what would be expected from previous studies based on immature or understory tree populations. We suggest the increased growth of adult trees in the presence of deer may be explained by increased nutrient inputs through deer fecal and urine deposits and the alteration of the competitive environment belowground through the reduction of understory vegetation by browsing.”

There are also studies that actually show that having too few deer negatively affects biodiversity. So the science is certainly not definitive on this issue. But the bottom line is this: deer killing programs do not permanently decrease deer population and may actually increase it over the long term, so no matter where the science (or your opinion) falls on biodiversity and forest regeneration, deer killing programs are not the answer.

We should note that this argument about biodiversity, forest regeneration, and carbon sinks is a red herring in an attempt to introduce a killing-for-fun provision into a climate and energy plan where it clearly does not belong, and in a town where it has been clearly rejected on other occasions. While hunting has gained some sort of hipster-chic among some, it is a huge stretch to convince most intelligent people that deer have anything to do with climate change.

Ten thousand years ago, 99% of zoomass was wild animals. Today, humans and the animals that we raise as food make up 98% of the zoomass. Any impact of any free-living animal on climate is modest, no matter the scale you use, compared to the impact from humans and the animals they raise to eat.

Further, free-living animals have zero carbon footprint. Every molecule of carbon they consume from the biosphere is returned to the biosphere. It is a closed-loop, 100% sustainable cycle, part of the natural carbon cycle that exists and has existed for billions of years. Only by taking sources of carbon from outside the biosphere (by digging up coal, oil, and natural gas from under ground), and releasing the carbon into the air by burning that material, can there be a carbon footprint. And by destroying approximately 36 football fields worth of trees every minute, humans shoulder the blame for destroying carbon sinks, not deer.

Finally, we should note that hunting, even bow-hunting, is not a carbon-neutral activity as practiced in 21st-century North Carolina. Hunters use fossil fuels in transporting themselves to their hunting locations with their equipment, removing and transporting the carcass to the processors, refrigerating the carcass, distributing the carcass, disposing of unused remains, and cooking the flesh. Additional fossil fuels are used in manufacturing hunting equipment and processing machinery.

Carrboro Energy and Climate Protection Task Force Recommends Deer Cull

deerThe Carrboro Energy and Climate Protection Task Force released its Community Climate Action Plan on November 4, 2015, which was presented to the Board of Aldermen on November 10, 2015.

Among their many recommendations, the Task Force stated the following:

“Local and other studies have shown that excess deer are adversely affecting the health of our forests by causing a decrease in plant diversity and aiding in the spread of exotic species. Soil studies have shown that the seed stores in areas with deer overpopulation are shifting from native wildflowers and woody plants to invasive plants and grasses. This threatens the ability of our forests to regenerate in a healthy way and continue to serve as diverse ecosystems and significant carbon sinks.  Deer overpopulation needs to be better managed to reduce negative impacts on forest regeneration and ecosystem health and biodiversity. While several options exist for managing the density of deer herds, studies have found that the least expensive and most effective method is through culling programs, often focusing on an urban archery program that can be tailored to a community and also provide food to people in need. Such programs have been safely and successfully implemented in Duke Forest, Chapel Hill, and many other towns in North Carolina. The Task Force recommends that Carrboro implement its own program to protect our forests from an expanding deer population that is too large now and may grow.” [page 38]

“Ecosystem Recommendation #2: Pursue Deer Herd Management [page 42]
“Studies have shown that excess deer are adversely affecting the health of our forests by overgrazing, causing a decrease in plant diversity, and aiding in the spread of exotic species. The current deer herd population is probably on the order of 5-10 times the optimal size for overall ecosystem health. The least expensive and most effective method for deer herd management is through culling programs, often focusing on an urban archery program that can be tailored to a community and also provide food to people in need. Such programs have been safely and successfully implemented in Duke Forest, Chapel Hill, Durham, Raleigh, Pittsboro and many other towns in North Carolina. While culling can be seen as a safety issue, there have been no documented archery related accidents in NC for the past 40 years.

“The NC Wildlife Resources Commission and others are available to advise the Town about the feasibility of creating a program that is tailored to the needs of Carrboro and addresses all concerns. The Task Force therefore recommends that Carrboro reopen the consideration of implementing its own deer herd management program to reduce negative impacts on forest regeneration and ecosystem health and biodiversity and protect our forests from an expanding deer population that is too large now and may grow. Specifically, the Task Force recommends that the Town consider submitting a letter of intent to participate in the Urban Archery Season program of the NC Wildlife Resources Commission.

Implementation Opportunities

    • A reduced/better managed deer population would:
      • Allow young trees and shrubs to grow, ensuring the continued existence of the forest and an increase in biodiversity;
      • Slow or stop the conversion of seed stores from native wildflowers and grasses to invasive species;
      • Improve the overall health of the deer population;
      • Decrease the incidence of deer/vehicle collisions
      • Provide food to people in need

Implementation Challenges

    • Contraceptives are expensive ($600-800/doe) and only work when the deer population is isolated and does not have an opportunity to migrate in or out of a given area.
    • Sterilization is expensive ($800-1,000/doe) and is currently not legal in North Carolina.
    • Culling deer herds is an emotional issue, despite clear science that shows deer herd management results in a healthier deer population, produces a more intact forest ecosystem, and has a positive impact on other wildlife species.
    • Culling is also a safety issue in the eyes of law enforcement, even though there have been no documented archery-related accidents in NC for the past 40 years.
    • A well-conceived and well-implemented public outreach and education campaign will require Board and staff approval and effort. This campaign is needed to get public buy-in, ensuring that citizens understand the purpose of, and need for, managing the deer population.
    • Resources Needed (human and material)
      • Administrative support from Town Staff with help from the Environmental Advisory Board.
      • Advice/guidance from other locales with an effective program already inplace (e.g., Chapel Hill, Durham, Raleigh, Pittsboro, and Duke Forest) and the NC Wildlife Resources Commission.
      • Promotional and educational materials.
    • Leadership
      • Policy leadership by the Board of Alderman.
      • Administrative support from existing Town Staff and the Environmental Advisory Board.
      • Partners
        • Town of Chapel Hill
        • Carolina North Forest Management
        • NC Wildlife Federation
        • Duke Forest
      • Fit with Items
        • Tree Coalition
        • Invasive Plant Management
      • Time Frame
        • Urban archery season is in the fall.
        • A decision could be made as to whether to look into for the fall of 2016 or 2017.
      • Next Step(s)
        1. Examine nearby urban archery plans. In particular, examine means for addressing public input, notification, and safety.
        2. Write up a draft urban archery plan.
        3. Craft public outreach and education campaign about negative impacts of deer overpopulation, benefits of deer herd management, and how an urban archery program would work.
        4. Board of Aldermen decide on public input process.
        5. Submit letter of intent to participate in the Urban Archery Season to the NC Wildlife Resources Commission.
        6. Finalize urban archery plan
        7. Implement urban archery season.
      • Evaluation Criteria
        • Number of deer culled and reduction of deer per square mile.
        • Improved health of deer population.
        • Reduction in number of deer-vehicle collisions.
        • Return of forest understory (increase in native flora, decrease in exotic species, and increase in plant and animal biodiversity).
        • Reduced loss of crops, gardens, and planted ornamentals.