Biogeography: The Effects Of Large Herbivores On Vocation
Geog 345
Biogeography
The Effects of Large Herbivores on Vegetation Introduction In eastern North America large herbivores such as deer and elk are some of the most respected and coveted of all wildlife species that inhabit the landscapes and forests. This is partially due to their size and beauty as well as their unparalleled value to hunters and outdoorsmen, seeking a challenge and a trophy. Although there is no shortage of hunters in the eastern United States, other than humans these large herbivores are not faced with many predators that are capable or preying on them. With very few predators to keep the populations of these large animals in check, their numbers grow very rapidly. With more large herbivores, that have …show more content…
even larger appetites, there comes and increase in demand for food and a decrease in vegetation and plants that are particularly palatable to these animals. With conservation and preservation on the brain, at first thought this may sound like a wonderful thing, but the extreme effects that these animals have on natural vegetation is truly astonishing. In this paper I will analyze and discuss the effects that large herbivores, especially deer and elk, have on the vegetation of eastern North America. By examining the information that others have already gained through close research and experimentation, I will answer the following questions:
• What ecological impacts can the over-population of these large herbivores have on the ecosystem?
• What are some management strategies that could be used in order to maintain ecosystem capabilities such as resilience, stability and diversity?
• How does this topic relate to biogeography?
Impacts
The dynamics of the food chain can be discussed in two general ways; “bottom-up” which involves plant health and quality, or starting from the bottom of the food chain, and “top-down” which involves predation, or starting at the top of the food chain (Nuttle 2011). Herbivores, as most of us know, sit somewhere right in the middle of the food chain. Carnivores feed on herbivores and herbivores feed on vegetation. Large herbivores such as deer and elk have been excluded from top-down population control in most of eastern North America due to insufficient hunting pressure from humans and a lack of natural predators (Nuttle 2011). This ultimately becomes a problem because herbivores as large as these have incredible appetites. With little pressure from predators their populations have grown to the point where their eating habits alone can actually delay the regeneration of forests and even change plant species composition. Although a slowing in forest regeneration goes along with top-down management and plant regulation, changes in actual species composition is specifically due to the preferences of these herbivores or what they consider to be palatable (Nuttle 2011). The over-lying concern of a change in plant species composition is that the plants that are particularly palatable to large herbivores become limited to the point where the carrying capacity of wildlife in that specific area will drop considerably or even that these plants could go through a local extinction. With large herbivores eating only the plants that taste good to them and the excessive rate at which they eat, these specific plants do not have enough time reproduce before they are eaten again. This will cause them to die off and be replaced by plants that deer do not eat (Augustine and McNaughton 1998). This not only effects the deer but it also affects all of the other organisms that eat these plants or depend on them for survival.
As I have stated, the two main ways that large herbivores effect vegetation are (1) delay of forest regeneration and (2) cause a change in plant species composition (Nuttle 2011). While these are two separate issues, in some instances the two of them can work together to cause even greater problems. In the instance of a greater disturbance such as a tornado or a clear-cut forest, the two of these negative effects could cause even greater problems (Hobbs et al. 1996, Nuttle 2011). If you combine slow forest regeneration, with deer and elk only eating what is palatable to them, the forests will only regenerate with the vegetation they do not eat. Therefore, all of the other organisms that depend on the vegetation, such as birds and insects, will not be able to come back and inhabit the new forest. This then affects the whole food chain and the entire ecosystem.
Management Strategies
The ability to understand the effects that the densities of these animals can have on plant communities and even the entire ecosystem is very important from a management perspective because manipulating animal densities is one of the best tools wildlife managers can use to positively change an ecosystem (Augustine and McNaughton1998). As significant as the impacts of deer may be, they are not an exotic or invasive species, therefore simply removing them will not restore an ecosystem to its natural conditions. Part of the problem with managing deer is that many of our forests today were started after massive areas were clear-cut for logging in the early 1800’s. During this time there were far less deer and in some areas, no deer at all. Now that the deer population has grown so much it is extremely hard for these forests to be restored (McShea 2012).
The population of an organism is determined by birth rates and death rates, and in order to manage that population you must impact at least one of those traits. With deer having so little in the form of predators, the main limit to their population numbers is access to productivity (McShea 2012). Extensive research has gone into figuring out a way to limit the access of deer to reproduce. An organization has actually invented a contraceptive for deer that would limit the ability of female deer to reproduce. It would cut down on reproductive behavior and stop the animal from ovulating. However, the only way this works is when it is injected by hand, which would mean that the deer would have to be captured and subdued (Augustine and McNaughton1998). This is highly impractical and until they invent a form of this product that could be consumed by the deer, it will likely not be employed.
Since large herbivores lack any significant predators in eastern North America, one way to possibly manage their populations while also allowing for forest regeneration and vegetation resilience, would be to introduce a new predator. When wolves were reintroduced to Yellowstone, their presence was noted to cause elk and bison to spend substantially less time out in the open and even less time feeding in general. This would help to lower the number of large herbivores while also allowing young saplings and vegetation that deer are particularly fond of to have the chance flourish and become more resilient. Within five years of their arrival wolves proved to be the number one source of female deer mortality in northern Minnesota (McShea 2012). The increase of predators was even proven to lower reproduction in elk because of an increase in stress hormones which lowered fawn production (McShea 2012).
It would be extremely beneficial to reestablish abolished predators to eastern North America to lower the population of large herbivores and reduce the stress on vegetation patterns. This theory however, is much easier said, than done. Politics and fear of these large predators would almost certainly stand in the way. Hunting is currently the number one way to manage the population of large herbivores in the eastern United States.
In areas that are not hunted and that have high productivity, densities of 30-50 deer per square km are not uncommon. In Hunted areas however, deer populations generally range from about 15-30 deer per square km, and even this is much higher than it should be (McShea, 2012). Not only is it effective and inexpensive but it is also great for the economy. Between license sales, land leasing, and gear purchases; hunting brings in approximately 25 billion dollars a year (McShea 2012). Currently in the United States there are numerous laws and regulations that go along with hunting that are strictly enforced. Most of them are made with the intentions of maintaining animal populations and not decreasing them. Perhaps, if we reevaluate the deer hunting regulations specifically, with a focus on decreasing deer populations, humans could act as a greater predator and in a way have the same effect that the introduction of wolves have on large herbivores in the …show more content…
west. How This Relates to Biogeography
This Topic relates to biogeography in numerous different ways. All of the key terms and concepts that were applied in these studies can also be applied to biogeography. Everything from; species mapping to disturbances, to ecosystem diversity, stability and resilience are concepts that an environmental manager and bio geographer should be comfortable with able use effectively.
When studying the effects that large herbivores have on vegetation, the first thing one must do is be able to map out these species and have a clear idea of the population densities. This comes in the form of species mapping. By understanding where the organisms that you are studying live and how large or small their populations are you can begin to form a plan and come to a hypothesis.
The effects that deer and elk have on vegetation are certainly disturbances to the ecosystem. In order to manage this problem one must understand the severity of the disturbance. Is it going to make the ecosystem stronger in the long run? Or is it simply going to go beyond a disturbance and turn into a stress on the environment that may be tough to recover from? At this point our ecosystems in eastern North America are not past the point of recovery, but if we do not begin to manage these issues more effectively they will likely evolve into severe issues.
The over-all goal of environmental management is to maintain ecosystem diversity, stability and resilience. These three key terms go hand-in-hand to ensure a successful and healthy ecosystem that will last well into the future. When managing the populations of large herbivores and keeping their populations at healthy densities we are allowing for healthy plant diversity and also giving vegetation a chance to grow and achieve some resilience. This way it can continue to flourish well into the future.
Conclusion
The effects that large herbivores have on vegetation are truly astonishing. Without an effective management plan our forests and ecosystems in eastern North America could go through some devastating changes that would affect the entire food chain and quality of life. While it is an extremely difficult task to manage these animals it is not impossible. We must continue to work on these issues and come up with something before it is too late. There are already numerous management plans that simply need to be refined a little. In order to overcome these issues however, we must act now before it is too late.
Bibliography augustine, D.
J., & McNaughton, S. J. (1998). Ungulate effects on the functional species composition of plant communities: herbivore selectivity and plant tolerance. The Journal of wildlife management, 1165-1183.
Horsley, S. B., Stout, S. L., & DeCalesta, D. S. (2003). White-tailed deer impact on the vegetation dynamics of a northern hardwood forest. Ecological Applications, 13(1), 98-118.
McShea, W. J. (n.d.). Ecology and management of white-tailed deer in a changing world. (2012). New York Academy of Sciences, doi: 10.1111/j.1749-6632.2011.06376.x
Nuttle, T., Yerger, E. H., Stoleson, S. H., & Ristau, T. E. (2011). Legacy of top-down herbivore pressure ricochets back up multiple trophic levels in forest canopies over 30 years. Ecosphere, 2(1), art4.
Roseberry, J. L., & Woolf, A. (1998). Habitat-population density relationships for white-tailed deer in Illinois. Wildlife Society Bulletin,
252-258.
Biogeography
The Effects of Large Herbivores on Vegetation Introduction In eastern North America large herbivores such as deer and elk are some of the most respected and coveted of all wildlife species that inhabit the landscapes and forests. This is partially due to their size and beauty as well as their unparalleled value to hunters and outdoorsmen, seeking a challenge and a trophy. Although there is no shortage of hunters in the eastern United States, other than humans these large herbivores are not faced with many predators that are capable or preying on them. With very few predators to keep the populations of these large animals in check, their numbers grow very rapidly. With more large herbivores, that have …show more content…
even larger appetites, there comes and increase in demand for food and a decrease in vegetation and plants that are particularly palatable to these animals. With conservation and preservation on the brain, at first thought this may sound like a wonderful thing, but the extreme effects that these animals have on natural vegetation is truly astonishing. In this paper I will analyze and discuss the effects that large herbivores, especially deer and elk, have on the vegetation of eastern North America. By examining the information that others have already gained through close research and experimentation, I will answer the following questions:
• What ecological impacts can the over-population of these large herbivores have on the ecosystem?
• What are some management strategies that could be used in order to maintain ecosystem capabilities such as resilience, stability and diversity?
• How does this topic relate to biogeography?
Impacts
The dynamics of the food chain can be discussed in two general ways; “bottom-up” which involves plant health and quality, or starting from the bottom of the food chain, and “top-down” which involves predation, or starting at the top of the food chain (Nuttle 2011). Herbivores, as most of us know, sit somewhere right in the middle of the food chain. Carnivores feed on herbivores and herbivores feed on vegetation. Large herbivores such as deer and elk have been excluded from top-down population control in most of eastern North America due to insufficient hunting pressure from humans and a lack of natural predators (Nuttle 2011). This ultimately becomes a problem because herbivores as large as these have incredible appetites. With little pressure from predators their populations have grown to the point where their eating habits alone can actually delay the regeneration of forests and even change plant species composition. Although a slowing in forest regeneration goes along with top-down management and plant regulation, changes in actual species composition is specifically due to the preferences of these herbivores or what they consider to be palatable (Nuttle 2011). The over-lying concern of a change in plant species composition is that the plants that are particularly palatable to large herbivores become limited to the point where the carrying capacity of wildlife in that specific area will drop considerably or even that these plants could go through a local extinction. With large herbivores eating only the plants that taste good to them and the excessive rate at which they eat, these specific plants do not have enough time reproduce before they are eaten again. This will cause them to die off and be replaced by plants that deer do not eat (Augustine and McNaughton 1998). This not only effects the deer but it also affects all of the other organisms that eat these plants or depend on them for survival.
As I have stated, the two main ways that large herbivores effect vegetation are (1) delay of forest regeneration and (2) cause a change in plant species composition (Nuttle 2011). While these are two separate issues, in some instances the two of them can work together to cause even greater problems. In the instance of a greater disturbance such as a tornado or a clear-cut forest, the two of these negative effects could cause even greater problems (Hobbs et al. 1996, Nuttle 2011). If you combine slow forest regeneration, with deer and elk only eating what is palatable to them, the forests will only regenerate with the vegetation they do not eat. Therefore, all of the other organisms that depend on the vegetation, such as birds and insects, will not be able to come back and inhabit the new forest. This then affects the whole food chain and the entire ecosystem.
Management Strategies
The ability to understand the effects that the densities of these animals can have on plant communities and even the entire ecosystem is very important from a management perspective because manipulating animal densities is one of the best tools wildlife managers can use to positively change an ecosystem (Augustine and McNaughton1998). As significant as the impacts of deer may be, they are not an exotic or invasive species, therefore simply removing them will not restore an ecosystem to its natural conditions. Part of the problem with managing deer is that many of our forests today were started after massive areas were clear-cut for logging in the early 1800’s. During this time there were far less deer and in some areas, no deer at all. Now that the deer population has grown so much it is extremely hard for these forests to be restored (McShea 2012).
The population of an organism is determined by birth rates and death rates, and in order to manage that population you must impact at least one of those traits. With deer having so little in the form of predators, the main limit to their population numbers is access to productivity (McShea 2012). Extensive research has gone into figuring out a way to limit the access of deer to reproduce. An organization has actually invented a contraceptive for deer that would limit the ability of female deer to reproduce. It would cut down on reproductive behavior and stop the animal from ovulating. However, the only way this works is when it is injected by hand, which would mean that the deer would have to be captured and subdued (Augustine and McNaughton1998). This is highly impractical and until they invent a form of this product that could be consumed by the deer, it will likely not be employed.
Since large herbivores lack any significant predators in eastern North America, one way to possibly manage their populations while also allowing for forest regeneration and vegetation resilience, would be to introduce a new predator. When wolves were reintroduced to Yellowstone, their presence was noted to cause elk and bison to spend substantially less time out in the open and even less time feeding in general. This would help to lower the number of large herbivores while also allowing young saplings and vegetation that deer are particularly fond of to have the chance flourish and become more resilient. Within five years of their arrival wolves proved to be the number one source of female deer mortality in northern Minnesota (McShea 2012). The increase of predators was even proven to lower reproduction in elk because of an increase in stress hormones which lowered fawn production (McShea 2012).
It would be extremely beneficial to reestablish abolished predators to eastern North America to lower the population of large herbivores and reduce the stress on vegetation patterns. This theory however, is much easier said, than done. Politics and fear of these large predators would almost certainly stand in the way. Hunting is currently the number one way to manage the population of large herbivores in the eastern United States.
In areas that are not hunted and that have high productivity, densities of 30-50 deer per square km are not uncommon. In Hunted areas however, deer populations generally range from about 15-30 deer per square km, and even this is much higher than it should be (McShea, 2012). Not only is it effective and inexpensive but it is also great for the economy. Between license sales, land leasing, and gear purchases; hunting brings in approximately 25 billion dollars a year (McShea 2012). Currently in the United States there are numerous laws and regulations that go along with hunting that are strictly enforced. Most of them are made with the intentions of maintaining animal populations and not decreasing them. Perhaps, if we reevaluate the deer hunting regulations specifically, with a focus on decreasing deer populations, humans could act as a greater predator and in a way have the same effect that the introduction of wolves have on large herbivores in the …show more content…
west. How This Relates to Biogeography
This Topic relates to biogeography in numerous different ways. All of the key terms and concepts that were applied in these studies can also be applied to biogeography. Everything from; species mapping to disturbances, to ecosystem diversity, stability and resilience are concepts that an environmental manager and bio geographer should be comfortable with able use effectively.
When studying the effects that large herbivores have on vegetation, the first thing one must do is be able to map out these species and have a clear idea of the population densities. This comes in the form of species mapping. By understanding where the organisms that you are studying live and how large or small their populations are you can begin to form a plan and come to a hypothesis.
The effects that deer and elk have on vegetation are certainly disturbances to the ecosystem. In order to manage this problem one must understand the severity of the disturbance. Is it going to make the ecosystem stronger in the long run? Or is it simply going to go beyond a disturbance and turn into a stress on the environment that may be tough to recover from? At this point our ecosystems in eastern North America are not past the point of recovery, but if we do not begin to manage these issues more effectively they will likely evolve into severe issues.
The over-all goal of environmental management is to maintain ecosystem diversity, stability and resilience. These three key terms go hand-in-hand to ensure a successful and healthy ecosystem that will last well into the future. When managing the populations of large herbivores and keeping their populations at healthy densities we are allowing for healthy plant diversity and also giving vegetation a chance to grow and achieve some resilience. This way it can continue to flourish well into the future.
Conclusion
The effects that large herbivores have on vegetation are truly astonishing. Without an effective management plan our forests and ecosystems in eastern North America could go through some devastating changes that would affect the entire food chain and quality of life. While it is an extremely difficult task to manage these animals it is not impossible. We must continue to work on these issues and come up with something before it is too late. There are already numerous management plans that simply need to be refined a little. In order to overcome these issues however, we must act now before it is too late.
Bibliography augustine, D.
J., & McNaughton, S. J. (1998). Ungulate effects on the functional species composition of plant communities: herbivore selectivity and plant tolerance. The Journal of wildlife management, 1165-1183.
Horsley, S. B., Stout, S. L., & DeCalesta, D. S. (2003). White-tailed deer impact on the vegetation dynamics of a northern hardwood forest. Ecological Applications, 13(1), 98-118.
McShea, W. J. (n.d.). Ecology and management of white-tailed deer in a changing world. (2012). New York Academy of Sciences, doi: 10.1111/j.1749-6632.2011.06376.x
Nuttle, T., Yerger, E. H., Stoleson, S. H., & Ristau, T. E. (2011). Legacy of top-down herbivore pressure ricochets back up multiple trophic levels in forest canopies over 30 years. Ecosphere, 2(1), art4.
Roseberry, J. L., & Woolf, A. (1998). Habitat-population density relationships for white-tailed deer in Illinois. Wildlife Society Bulletin,
252-258.