The Beaver

July 8, 2020

Introduction 

     WFF’s goal is a sustainable population while protecting the environment from ecological harm and the economic damage. The beaver is a unique animal in that its overabundance can cause such acute and documented problems. The harvest of beaver has been done for centuries with large environmental and economic significance. This paper will explore the environmental harms of beaver if populations are left unchecked. The economic impacts will also be examined, as many federal, state, and local governments pay to have beaver removed, and private land/property owners bear large costs when beaver damage property or crops. The harvest of the animal is a science that is well researched and studied. Regulations and safety are explored in this paper.

Environmental Impact 

Greenhouse Gases​

The effects of global warming continue to be a point of concern among people across the globe. Carbon budgets are being established, and research is being done in many sectors to find ways to curtail the continuously rising levels. With this research has come information about how Beaver and their habits interact with rising carbon and methane levels. The Beaver contributes to an increase in greenhouse gases in two ways: creating shallow ponds that emit methane (CH4), and destroying trees which sequester carbon and protect streams.

Beavers dam streams to create shallow ponds that are easy to swim in. The flooding created by the dam, the shallow depth, and the large surface area create a warm and anaerobic environment allowing bacteria to produce methane [1, 2]. Because the pond is shallow, there is little opportunity for methane oxidation, further contributing to the problem [1]. These ponds have properties of wetlands and open-water systems, but emit more methane than other types of wetlands [3]. As of 2015, it is believed the beaver population has reached 30 million with the creation of 9,500 - 42,000 km2 of new pond habitat [4]. With this increase in beaver population comes an increase in methane gas. Whitfield et. al. found that “beaver mediated aquatic CH4 emissions have increased ~400 fold since the early twentieth century. [4] In 2000, emissions had reached 180,000 - 800,000 metric tons per year. Beaver account for approximately 15% of the methane production from wild ruminants when using the maximum estimate of 800,000 metric tons per year [5]. In addition, the beaver ponds can raise the water table around the pond which has been shown to increase CH4 emission for the soil [6,7]. This suggested that the previously suggested methane estimates may be larger than reported. 

As the temperatures in Arctic tundra regions warm, beavers are moving in and building dams [8]. In beaver-influenced waterbodies, the water surface area increased by 14.3%, where in non-beaver-influenced waterbodies the water surface area increased by only 4.6% [8]. Jones et al reports that the increasing surface water area was “resulting primarily from an increase in beaver dams.” Water impoundment (reduction/refusal of flow) is known to promote permafrost degradation [9]. Though the full affects have not yet been discovered, the permafrost thaw mobilizes carbon that was previously stored [10]. Initial studies have found that permafrost carbon emissions could create substantial impacts on the climate system [11]. Abrupt thaw, such as that which can be caused by beavers, can impact many meters of permafrost soil whereas gradual thaw only affects the soil by centimetres [10]. This can allow for increased carbon and methane missions. The simulations done by Turetsky et al showed that abrupt thawing could release 625 million - 960 million tons of CO2 per year [10]. While the abrupt thawing cannot be fully attributed to the beaver, the beaver certainly contributes to the problem. It is also important to note that in addition to the carbon released when the permafrost thaws, methane is released. The methane comes from both the thawing of the permafrost and the creation of a habitat optimal for bacteria to produce methane as mentioned above. As Turetsky et al puts it “thaw lakes and wetlands are methane hot spots [10].”

It is well known that beavers kill trees as they use them for food and dam building materials. This deforestation can be harmful as it eliminates the carbon sequestering capability of the tree and allows contaminates to get into stream water. A single mature tree absorbs carbon dioxide at a rate of 48 pounds per year. Though the number of trees a beaver takes is difficult to quantify to varying sizes, Johnston and Niaman reported that in Minnesota, “intense foraging by beaver decreased tree density and basal area by up to 43% near ponds [12]. In addition to sequestering carbon, trees keep streams clean. A case study by Sweeny and Newbold showed that a forest buffer keeps 43% of sediment and 27% of nutrients such as nitrogen from entering a stream [13]. The same study concluded that stream side forests “enhance the quality and health of in stream physical, chemical, and biological characteristics” A healthy stream is able to sequester carbon, metabolize organic matter, and degrade and process pollutants [13].

 

Impact on Trout

The effect of beaver ponds on the ecosystem can vary based on location. While the pond can create habitat for birds, reptiles, amphibians, and even deer, it may disrupt fish migration, eating, and reproduction habits. During the warm season, the shadow nature of the beaver ponds may lead to increased temperatures of the water which can prove deadly to trout. Additionally, the ponds may experience increased acidity and decreased oxygen content of the water. The dams become a problem in the fall when fish are traveling upstream. If the trout are not able to get over the dam, they not be able to spawn. For fish that are able to spawn, hatching of the eggs may prove difficult as the slow moving water may freeze and kill trout eggs [14]. While there are benefits to having beaver for some ecosystems, it is important to control beaver populations for the benefit of other species.

 

Economic 

Negative environmental and economic impact of the beaver is quite well documented. Deforestation, increased greenhouse gases, changes in water chemistry, infrastructure damage and many other problems are currently associated with beaver overpopulation. Currently in North America, Federal, State and Local, and private organizations are paying bounties for their removal to prevent these environmental and economic issues. 

 

Federal 

    The National Wildlife Refuge System encompasses 92+ million acres in the united states. Regulated trapping has been used to promote sustainable use of wildlife as well as manage refuges. The Northeast Association of Fish and Wildlife Agencies reports that between 1992 and 1996 there were 487 mammal trapping programs on the National Wildlife Refuges [15]. 

    The Federal government utilizes the trapping of beaver to protect other species. The impact of beaver on trout has been mentioned above, and there are many other species that the trapping of beaver has helped. The Northeast Association of Fish and Wildlife Agencies reports that beaver have been trapped to promote the restoration of the Pink Lady Slipper and the Pitcher Plant [15].

 

State and Local 

    State and Local governments provide funding for beaver removal to protect their roads, bridges, and wells. This funding is well documented and budgeted for by state and local governments. The USDA reports that individual townships may pay $600 per year to protect roadways. It is also reported that “Wisconsin Wildlife Services funding for beaver damage management is over $400,000 annually.” [16]

    Roads, railroads, and fish habitat as being some of the complaints surrounding beaver in Wisconsin. Arner and Dubose estimated the economic losses from beaver-related activity to exceeded $4 billion in the southeastern U.S. over the previous 40 years [17]. A study by Miller reported the annual beaver-related damage cost between $75 and $100 million in the U.S.[18]. It is clear that it is beneficial for State and Local governments to manage beaver levels to keep them at a healthy population level and also minimize damage caused by over population. 

 

Private

    Private individual and groups in Norte America provide Funding for nuisance Beaver removal. Individual property owners and wildlife protection organizations are the primary source of this revenue.

    Private individuals have become quite instrumental in funding the harvest of beaver in North America. Nuisance beaver trapping in North America is no longer a cottage industry. Almost every area beavers inhabit has people in the employ of controlling them. Thousands of these small firms can be found on an internet search. It is very difficult to ascertain from current data where the beaver are removed from (residential or agricultural). Antidotally it would appear that is somewhat balanced between the two in terms of actual case amounts; however, it would seam the agricultural calls typically involve more actual beaver removals.

    Private landowner beaver removal is often associated with flooded corn crops in semi-forested areas. Beavers can make quick work of a small grove of trees in a stream setting. Row crops are quickly flooded, ruining crops and their subsequent value. Paid nuisance removal is the only answer in this scenario. 

    Market prices of beaver pelts are far below what a professional trapper needs to profitably remove the animal. A typical beaver removal cost upwards of $150 while the hide is valued under $10, making the hide a by-product of a successful removal. 

    Residential removals are often in rural settings or where suburbs and forested areas intersect. Trees and shrubs are being destroyed including high value ornamental landscaping. The Northeast Association of Fish and Wildlife Agencies (NAFWA) reported on Chelmsford, Massachusetts, a town that banned trapping during the late 1980s. While before the ban there were minimal complaints of beaver damage, after the ban residents saw the beaver population grow rapidly. The damages grew with the population. Beaver dams resulted in the flooding of houses and roadways and the shut down of wells. NAFWA reports that individual landowners had incurred “tens of thousands of dollars in damages to private wells, septic systems, lawns, and roadways.” Regulated trapping was restored, and the beaver damage complaints were again under control. The goal was not to eliminate beaver completely, rather “manage beaver resources as assess, not liabilities” (NAFWA). Regulated trapping allows for the beaver to be maintained at levers suitable for the habitat and minimizes property damage [15].

 

Trapping Regulations 

Modern trapping equipment has progressed far beyond the crude devices that many may associate with the practice. In fact, trapping, and the equipment used, is bound by strict regulations to protect people, animals, and the environment. Wildlife biologists, the American Association of Wildlife Veterinarians and the  American Veterinary Medical Association support the use of trapping in wildlife management, as does the vast majority of the public and many other conservation organizations [19]. For years, the fur industry has been committed to safe, humane, and sustainable trapping. 

Responsible Trapping

Three methods are commonly used for beaver trapping: a leghold trap, conibear trap, or a live trap. Leghold and conibear traps are different in how they capture/kill the animal, but both are used in a similar fashion. When triggered, a conibear trap clamps the animal between two bars. This usually kills the animal very quickly, if not instantly. A leghold trap grabs the leg of the beaver when triggered and holds the animal underwater where it eventually drowns. This is quite different from the misconception that leg hold traps leave an animal in pain until the trapper arrives to dispatch it. Live traps are less common and somewhat different. A typical rectangular cage or a clamshell-like trap are both used for beaver, which restrain them without harm until the trapper arrives to dispatch them. [20] What may be surprising to many is that traps used by trappers are the same devices approved by governments for relocation efforts and studies. When removing wolves, coyotes, raccoons, and other animals, a leghold trap is a common tool among researchers. [21, 22]

Further, when trapping beaver using a leg-hold or body gripping trap, it is imperative that the animal dies in a short period of time. With a prolonged struggle, an animal as large as a beaver could free itself from the trap. For this reason, many trappers will use setups or “sets” that are inherently designed to be lethal as fast as possible with minimal opportunity for any struggle by the animal. The United States and Canada have dedicated organizations such as the National Trappers Association and the Fur Institute of Canada that educate trappers in order to take game in the most appropriate way. ”Trapper education workshops and training programs are delivered under national curriculum guidelines and managed by trapping and wildlife associations. They cover best management practices, rules and regulations, trapper safety, animal welfare, and pelt/meat/by-product preparations.” [23]

Regulation

Since 1998, the Agreement on International Humane Trapping Standards (AIHTS) has been enforcing what types of traps could be used, and the standards set for them. This was an agreement made between Russia, the European Union, and Canada that allows for the import of furs into Europe, provided they are obtained in alignment with the AIHTS [24] . For a beaver, a lethal trap must render the animal insensible and unconscious within 300 seconds. [25]. The U.S. and the E.U. have also signed a similar agreement detailing the methods approved for taking beaver. Both agreements include humane guidelines as well as a certified list of traps. [26]

Research

The Fur Institute of Canada and the Alberta Research Council have been developing and testing traps since 1981 with the mission to only allow use of the most humane traps. “The primary Objective of the Trap Effectiveness Project evolved from development of humane traps to development and application of technologies to rate trapping systems against the AIHTS established in 1997. Trapping systems used in Canada must conform to these standards in order to maintain the European Union wild fur markets and keep Canada’s fur trade viable” [27].  By using Computer Simulation Models of both the traps and animals, researchers were even able to hundreds of traps without using animals as well as minimizing costs [28, 29]. State of the art facilities and dedicated research ensures that no animal will suffer undue harm when taken by a trap.

Safety

A common objection and misconception that is held about beaver trapping is the danger it poses to people, pets, and non-target species. Trapping accidents of this nature are rare, and there are regulations in place to prevent them. Leg hold traps are lawfully required to be submerged when set, making them unlikely to affect anything other than the targeted beaver. Conibear or “body grippers” are usually submerged as well, designed to be triggered when a beaver swims through them. Additionally, they can be configured to catch animals no smaller than a beaver. While risk of an accidental encounter with a beaver trap is low, quickly freeing the animal will release it with little harm. 

Culture 

    Historically, the beaver has been at the center of the fur trade for centuries, fueling the exploration of North America and trade with indigenous people. Its versatile pelt is used for fur and felt hats, coats, and fur trimmings. In fact, the beaver pelt was essentially the currency of early North America. That strong tradition of trapping the U.S. and Canada’s most recognizable furbearer continues today. The tradition represents more than any monetary reward, although it remains important. The indigenous people understood the important give and take relationship of man and nature. Take too much, and the population may be at risk. Take too little, and the population grows weak and vulnerable. With the correct understanding, trappers are able to mimic the native ideology and harvest the surplus, allowing the remaining beavers to thrive at their full potential. Today’s trapper is a frontline environmentalist that senses the ebb and flow of wildlife populations he pursues. They are passionate about their pursuit and the propagation of the species they trap, with a love and appreciation of any animals they are fortunate enough to catch. Although the fur trade is very different than it was in the 1600’s, the spirit lives on through today’s trappers who dedicate themselves to the harvest of these animals as well as their protection. Trapping brings people together at conventions, forums, and even the fur buying depots to share knowledge and stories from days spent on the trapline. 

 

Summary

The beaver is North America’s most recognizable and historic furbearer, the center of a centuries long story of exploration and trade, and to protect it is our responsibility. By  supporting the harvest and utilization of beaver, we support a sustainable, highly regulated, and beneficial industry dedicated to the long term support of not only the beaver but other furbearers as well. Harvesting nature’s surplus allows for a period of compensatory growth, giving way to healthier populations of wildlife. The goal of responsible trapping is to maintain sustainable populations while protecting the environment from ecological harm and economic damage. Trapping regulations ensure that this is not only beneficial to the harvester, but to the beaver as well. The use of the beaver is ecologically and economically positive, and it supports a culture that has been around for centuries.

 

 

Works Cited 

  1. McComb W.C., Sedell J.R., and Buchholz T.D. Dam-site selection by beavers in an eastern Oregon basin. Great Basin Naturalist 1990;50:273-281 

  2. Naiman R.J., Melillo J.M., and Hobbie J.E., Ecosystem alteration of boreal forest streams by beaver (castor canadensis). Ecology 1986;67:1254-1269. 

  3. Roulet N.T., Ash R. and Moore T.R. Low Boreal wetlands as a source of atmospheric methane. Journal of Geophysical Research-Atmospheres 1992:97: 3739-3749.

  4. Whitefield C.J., Baulch H.M., Chun K.P., and Westbrook C.J. Beaver-mediated methane emission: The effects of population growth in Eurasia and the Americas. Ambio 2015;44:1 7-17. 

  5. Lelieveld J., Crutzen P.J., and Dentener F.J. Changing concentration, lifetime and climate forcing of atmospheric methane. Tellus 1998;50B:128-150. 

  6. Westbrook C.J., Cooper D.J., and Baker B.W. Beaver dams and overbank floods influence groundwater-surface water interactions of a Rocky Mountain riparian area. West Resources Research 2006;42:1-12. 

  7. Moore T.R. De Young D., Bubblier J.L., Humphreys E.R., Lafleur P.M., and Roulet N.T. A multi-year record of methane flux at the Mer Bleue Bog, southern Canada. Ecosystems 2011;14:646-657 

  8. Jones B.M. et al. Increase in beaver dams controls surface water and thermokarst dynamics in an arctic tundra region, Baldwin Peninsula, northwestern Alaska. Environ. Res. Lett. 2020;15. 

  9. Arp C.D., Jones B.M., Groose G., Bondurant A.C., Romanovsky V.E., Hinkel K.M., and Parsekian A.D. Threshold sensitivity of shallow Arctic lakes and sublime permafrost to changing winter climate. Geophys. Res. Lett. 2016;43:6358-65 

  10. Turetsky M.R. et al. Carbon release through abrupt permafrost thaw. Nat Geosci. 2020;13:138-43. 

  11. Grosse G., Jones B.M., Arp C.D. Thermokarst lakes, drainage, and drained basins. Treatise in Geomorphology. 2013;8:235-53. 

  12. Johnston C.A., Niaman R.J. Browse selection by beaver: Effects on riparian forest composition. Canadian Journal of Forest Research 1990;20:1036-43. 

  13. Sweeney B.W., and Newbold J.D. Streamside forest buffer width needed to protect stream water quality, habitat and organisms: A literature Review. Journal of American Water Resources Association, 2014;50:560-584. 

  14. Cook D.B. Beaver-trout relations. Journal of Mammalogy 1940;21:397-401. 

  15. Northeast Association of Fish and Wildlife Agencies. Furbearer Management in the Northeast.

  16. USDA-APHIS- Wildlife Services. Cooperative Beaver Damage Management Program. 

  17. Arner D. H., and Dubose J.S. The impact of the beaver on the environment and economics in the southeastern United States. Int. Wildlife Congress, The Wildlife Society, Bethesda, MD. 1979; 241-247 

  18. Miller J. E. Control of beaver damage. Proc. East. Wildl. Damage Contr. Conf. 1983;1:177-183. 

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  20. Albertaregulations.ca. 2020. Alberta Guide To Trapping Regulations - General Regulations. [online] Available at: <http://albertaregulations.ca/trappingregs/gen-regs.html> [Accessed 7 July 2020].

  21. Aphis.usda.gov. 2020. [online] Available at: <https://www.aphis.usda.gov/wildlife_damage/nepa/risk_assessment/RA4%20Foothold%20Trap%20-%20Peer%20Reviewed.pdf> [Accessed 7 July 2020].

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  25. Agreement on International Humane Trapping Standards.

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  29. Hiltz, M. and Roy, L., 2001. Use of anesthetized animals to test humaneness of killing traps. a. Wildlife Society Bulletin , 29(2):606-611.