Apex Consumers

The first example of human manipulation of changes within the biosphere is through expansion. The rapid growth of the population has led to expansion in development; the need for more space is causing strain on other living organisms such as plants and animals. Human procurement of forest, grass, and wetlands has weighed on the animal population heavily. As a result of this domination, animals have lost areas they use to thrive in, causing migration and in more serious cases extinction. Animals are a prevalent source of protein for humans, and when a species is threatened by extinction, it not only disrupts the balance of the ecosystem, but it also disrupts the food chain. The more resources that are required to sustain human life, the bigger the need to migrate to surrounding areas in a short period of time (Haines).

of the food chain. This would cause their numbers to rise, which would lead to irreparable damage to the ever-fragile ecosystem.

The scale and pace of change is dramatic; for example, the extinction of species is occurring at around 100-fold pre-human rates4. The population sizes of vertebrate species have, on average, declined by half over the last 45 years5. More than 2.3 million km2 of primary forest has been felled since 20006. About

Since the reintroduction of wolves into Yellowstone they have created an astounding and advantageous trophic cascade. A trophic cascade is an ecological phenomenon triggered by the addition or removal of top predators and involving reciprocal changes in the relative populations of predator and prey through a food chain. These often result in dramatic changes in ecosystem structure and nutrient cycling. In a three-level food chain, an increase (or decrease) in carnivores causes a decrease (or increase) in herbivores and an increase (or decrease) in primary producers such as plants and phytoplankton according to briticanna (how to make better). The entire ecosystem was able to become whole again because the wolves, a key species, were reintroduced. Now this may seem weird, a predator comes into the area a begins to kill animals, how can this be beneficial in any way? Well the fact of the matter is that it is extremely beneficial. The reason being the problem in Yellowstone was the overpopulation of the elk. These elk had no predators, they were free to roam and reproduce, and they did this very well. Now elk are also a

“Restoring an ecologically complete ecosystem in Yellowstone requires the return of willows--and with them, beavers. There's a clear threshold for ecosystem recovery. Willow stands must be more than 6 feet tall, the scientists found. That height is important, says Marshall. Then willows are beyond the reach of browsing elk, and can serve as seed sources for new young willows. Once willows have returned, beavers will gnaw down a certain number of them to build dams. The dams will further slow stream flow, allowing yet more willows to grow. The results offer new insights on the role of wolf-driven trophic cascades in the Yellowstone ecosystem, says Hobbs. Trophic cascades like that in Yellowstone occur when predators--or the lack thereof--in an ecosystem change the abundance or alter traits of their prey, in turn affecting the next lower trophic level.” ("National Science Foundation", 2013)

I am taking a class called global environmental issues and heard about how reintroduction of wolves has had very positive impact in Yellowstone, but we did not go much deeper than just stating so.

Extinction: Most species become extinct because they can’t cope with the environmental change, and also because of introduced species that turned into competitors for

If a predator organism was removed from an ecosystem, it would allow the prey population to increase which could lead to not having enough food for these organisms to eat. For example, if wolves were eliminated from the taiga biome than there would be a dramatic increase in the population of moose. This would result in the moose not having enough jack pine and could lead to starvation. The wolves would then have to eat more rabbits, elk, and voles which would decrease their population and starve the organisms that rely on these animals.

Whitetail deer have come to be known as a keystone species, species known for affecting other organisms in an ecosystem. Deer are known as a keystone species in forest habitats such as in the Eastern United States because they are capable of destroying potential forest habitat of other organisms (McShea and Rappole, 1992). For example, deer have a negative impact on forest ecosystems by trampling and over browsing over vegetation, without creating any habitat for other native species. Throughout the eastern United States, the abundance of white-tailed deer (Odocoileus virginianus) has increased dramatically over the last century (Taggart and Long, 2015). Population increases could be due to increased habitat fragmentation from land development, reduced predators and/or hunting pressure. Individual deer ranges varied during seasonal times, deer movements are usually greatest during the peak breeding months from late fall through winter (Williams et. al, 2012). Regardless of the cause, high deer densities can have significant effects on plant communities such as plant decay and/or even death. Deer consume a large amounts of plant biomass (leaves, buds, flowers and fruits) and directly reduce the growth, reproduction, and survival of herbaceous and woody plant species (Shen et. al, 2016). The impacts of white-tailed deer on forests along the Eastern United

The area of Yellowstone National Park has a long history of inhabitants, even before it became the nation’s first national park. In the area now known as Yellowstone National Park, wolves were once very prominent. However due to westward expansion in the 1800s, agriculture began to increase. This led to the wolves that once thrived in this area to being practically completely removed. The increase in agriculture in this region led to a lot of the wolves’ prey becoming reduced or eliminated. Since the wolves had a decrease in prey, the wolves began to prey on domestic animals, which then resulted in humans eliminating the wolves almost completely. By the 1930s the wolf was eliminated from the area. This was before people had an understanding of how ecosystems work and the interrelation of species. Now that the wolves were gone, elk then became overpopulated. A lot of the vegetation began to disappear as well due to the overgrazing of the elk. However after about a 70-year absence, in 1995 the wolves were carefully brought back to Yellowstone. When they brought the wolves back to the park, there was not just an effect on one species or one area but rather they affected the entire ecosystem of the area. I will discuss their effects on areas such elk, beaver colonies, scavengers, aspen trees, willow trees and cottonwood trees.

In this article, authors William Ripple and Robert Beschta focus on the issue of predation and the way it affects biodiversity and otherwise alters ecosystems. While many other studies have stressed the lethal effects of predation by carnivores, the authors of this study have chosen to focus on how nonlethal outcomes of predation affect the structure and function of ecosystems. The authors give two main objectives to their study: first to provide a short synthesis of the potential ecosystem responses to predation risk in a three-level trophic cascade involving large carnivores, hoofed animals, and vegetation; and secondly to present research that centers on wolves, elk, and woody browse species in the northern area of Yellowstone National

In Yellowstone National Park, scientists have been carefully documenting the impacts of wolves on the ecosystem, noting many changes for the better since reintroduction, (Berger et al. 2008; Beschta and Ripple 2010). As the ecosystem depends on the Gray Wolf to properly function predation, the wolves also regulate distribution and group size of each species, which impacts overall native biodiversity. Wolves primarily prey on large hoofed mammals such as deers, elk and moose. By preying on the most vulnerable (diseased, young, old, weak or injured) individuals, wolves can help keep prey populations more healthy and strong, (Carbyn

Since the beginning of life itself, some species have lived and prospered while other species have gone extinct never to be seen again by mankind. Because of this, some would claim that extinction is natural and not significantly problematic to the world that we live in. Others, however, understand that due to climate change, habitat loss, and poaching, more and more species are becoming endangered which leads to a chain reaction that can be devastating to ecosystems. Species such as the Chinook salmon, gorillas, tropical sharks, and polar bears are all directly affected by climate change, species such as northern spotted owls, Sumatran tigers, and lemurs are greatly harmed due to habitat loss, and species such as the sea turtle, Javan rhinoceros, African elephant, and the Red-Fronted Macaw are all affected by poaching driving them all closer and closer to becoming extinct.

It’s clear that a great extinction is coming from the evidence of the destruction of other species around us. The choices made by the human race have too often negatively affected the surrounding species. Tracy Wilson, the site director for HowStuffWorks.com, in an article for Animal Planet, states that

Habitat destruction, deforestation, ozone depletion, global warming, and poaching. These actions and ecological happenings are creating a world where animals are going extinct at rapid rates. Our world is on the brink of what scientists believe is the sixth mass extinction. Unlike the five previous mass extinction, the latest one killing a majority of the dinosaurs, the main causes for this current extinction are anthropogenic reasons, not natural events.