Yellowstone national park was established on March 1st 1872. YNP is a wilderness recreation area with, alpine rivers, forests and canyons. YNP is also home to many animal species. In about a 16 year time period, Wolves have benefit about every animal in the ecosystem. 1924 was a point at YNP where wolves were exterminated. Once the wolves were gone, YNP went in the wrong direction. In about 1929 the park’s ecosystem was beginning to change. The elk were under enemy release, once the wolves were missing. There now was only a small amount of predators left at YNP. Aspen and cottonwood begun to appear dry and old. Without the wolves to control it, the elk population had grown and became fearless. The elk consumed anything they could find. That included the willows close to the stream that were important. Interspecific competition was now in effect, when the carrying capacity of elk had reached the maximum. Because the elk population had grown so big, the willow population was nearly gone. Researches at YNP tried to find a reason for why the aspen inside the park had been affected. Researchers looked at density independent factors such as forest fires but they realized that the problem in YNP was the lack of predators. Elks population was growing rapidly but there were some limiting factors that kept the population from passing the carrying capacity. This was because of density dependent limiting factors. One thing that limited the growth of the elk was because there was not enough willow to feed the growing elk population. At location B in the YNP research pictures, there was a great example of what it was like without the wolves. The aspen and willow trees were being eaten from the Antelope and Mule Deer. Both those animals have a similar job so in other words, a functional redundancy. Both the animals were eating over the amount they should have been eating. The resilience of trees was hard because of the low biodiversity of the plants. Now the ecosystem is being controlled on what plants are left for the ecosystem to feed on. Bottom up control now came into play. Beaver and bison were now starving because elk was eating willows and aspen. A trophic cascade had begun because of this. Beavers are keystone engineers. Beavers could now no longer create dams, so the aquatic life in the water had disappeared. Beavers were now competitively excluded because they could no longer eat. Beaver dams were very important to the ecosystem because, water fowls, amphibians and the muskrat family would live in the beaver dams. These aquatic animals no longer had a home to love in, so they did not survive. Rivers and streams were also affected. The beavers were not able to build dams, so there were no restrictions in the streams. The streams now became unhealthy. Also because of this, riparian vegetation that was around the streams, vanished. Grizzly bears were also affected deeply by this. Grizzly bears were now fighting for fish in the streams. They would also fight for territory near the water. This is known as intraspecific competition. Grizzlies use their fundamental niche because they can go anywhere and be feared by everyone. This is why they are the top apex predator. Wolves were reintroduced to the park around 1974. With the wolves reintroduced, almost every species was under recruitment. Now the theory of top down control was back in effect. With the wolves back, every trophic level increased in biodiversity and richness. The amount of herbivory was cut down and began to even out. With the wolves reintroduced, the elk population decreased by a big number. The wolves being back it also impacted the fox, raven and coyotes. They were now feeding of the carcuses that the wolf had killed. Between the wolf and the raven, predator mediated coexistence occured. Raven would circle a flock of elk. Then the wolf would go and hunt in that location. Wolves are a keystone predator. Elk were pressured with the ecology of fear by the wolves. Because of this it made the elk afraid to go out and gaze. With the reintroduction of the wolves, many small animals came back. We saw an increase in songbirds and beetles. The song birds and beetles shared many of the same resources. Both these species would share the young cottonwood trees for a resource. The beatles used the leaves off the tree for food. While the songbirds used the trees for protection and shelter, to build their nests. Resource partitioning was used to better both of the species. All in all humans had a negative effect on the ecosystem in YNP. Now that the wolves have been back, nature is remaking its course and it is thriving.