Beavers and Bison

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The elimination of two animal groups from Yellowstone National Park changed the course of rivers and decreased plant and animal diversity. What two animals had such a big impact? Creatures that humans have long considered competitors and pests: wolves and beavers.

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Creating Wetlands

When beavers make a dam, they slow the flow of water in the stream and, subsequently, a pond or area of wetland is formed. Roughly 85 percent off all native North American fauna rely on wetlands, so they're extremely important to the ecosystem. These wetlands also slow the runoff of rains, thereby storing water that would otherwise be lost.

Tree Cutting

When beavers fell trees to make dams and lodges, they have a positive effect on their ecosystem. After felling aspens -- beavers' tree of choice -- the stumps grow new shoots, which are unappetizing to beavers but are the ideal food for moose and elk populations. When they cut down trees, they also bring more light to the forest floor, which allows trees that need a lot of light to grow -- such as hazels and alders -- an opportunity to thrive. This encourages diversity of plant life.

Sediment and Water Filtration

When a dam slows the water and creates a pond or wetland, it also slows the movement of the sediment in the stream and causes it to build up in the pond. This nutrient-rich sediment either provides food for those creatures who live at the bottom of the pond or slowly seeps into the surrounding soil. Once the beavers move on and their dam breaks down, the water will drain, leaving behind an extremely lush meadow full of rich soil. Dams also filter the water that runs through, improving its quality.

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Great herds of bison once roamed North America between the Appalachian Mountains on the east and the Rockies on the west. It is estimated that around 30 million bison roamed the continent when Columbus landed. The herds were so large that the bison became a symbol of the seemingly endless resources of the continent.

                                                                              -What have we Done ?-

                                        Other then nearly lost touch with reality, because Nature is the only Real Reality


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American Indians called the beaver the “sacred center” of the land because this species creates such rich, watery habitat for other mammals, fish, turtles, frogs, birds and ducks. We now know that beaver damming provides essential natural services for people too.

Beavers prefer to dam streams in shallow valleys, where the flooded area becomes productive wetlands.These cradles of life support biodiversity that rivals tropical rain forests. Almost half of endangered and threatened species in North America rely upon wetlands. Freshwater wetlands have been rated as the world’s most valuable land-based ecosystem.

Beavers reliably and economically maintain wetlands that sponge up floodwaters, alleviate droughts and floods (because their dams keep water on the land longer), lesson erosion, raise the water table and act as the “earth’s kidneys” to purify water. The latter occurs because several feet of silt collect upstream of older beaver dams, and toxics, such as pesticides, are broken down by microbes in the wetlands that beavers create. Thus, water downstream of dams is cleaner and requires less treatment for human use.

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A keystone species is a species that is particularly important to the functioning of the ecosystem and without it the ecosystem would change drastically, possibly reducing biodiversity, soil fertility etcetera. The American Bison is a keystone species to the grasslands of the Great Plains for many reasons: their distinct wallowing, trampling, migration and eating patterns and many more. Many are unaware of how important the American Bison is because “Knowledge of the bison's role in tall grass prairies is lacking because the extent of this grassland and the abundance of its dominant ungulate have declined dramatically and in tandem over the last 150 years… The near-simultaneous reduction in herbivore abundance and grassland extent left little opportunity to assess bison-tallgrass prairie interactions (knapp 39-50). However, the more studies that emerge that study how Bison interact with their ecosystem, it is clear that they play a critical role. 

The American Bison’s distinctive trampling and wallowing leads to “Topsoil displacement and subsequent compaction eventually result in microsites with low pH, high soil moisture, and high claycontent relative to the surrounding prairie  Studies have shown that species diversity is elevated in a landscape with bison wallows” (knapp 39-50). Bison also influence the grassland ecosystems as “Bison can substantially alter nutrient cycling processes and patterns of nutrient availability in tallgrass prairie. Their effects on nitrogen cycling are critical because nitrogen availability often limits plant productivity in these grasslands (Seastedt et al. 1991, Blair 1997, Turner et al. 1997) and influences plant species composition (Gibson et al. 1993, Wedin and Tilman 1993). (knapp 39-50). The nitrogen cycle is one that is especially important for plant life and their is ample proof that Bison only improve the nitrogen cycle  further contributing to the ecosystem.