What would you say if I told you that one species of plant or animal could determine the overall health of an ecosystem? Take that one species out of the picture and the entire ecosystem could face a collaspe. In one book, they mention that this idea of a keystone species is just a theory. So what is a keystone species? According to wikipedia, a keystone species is a species that plays a critical role in maintaining the structure of an ecological community and whose impact on the community is greater than would be expected based on its relative abundance or total biomass. Just as an example say we remove Krill from the Antarctica food chain, their removal as a species would disrupt baleen whale species, penguin species, fish species, and seal species. Not to mention that it could also impact the populations of invertebrates. The keystone species may not be a prey species. Another example given is the example of a gopher tortoise. Gopher tortoises dig burrows. These burrows create micro-enviroments where other creatures take shelter or live. A wide variety of other animals make use of these burrows. They include mammals, inverts, amphibians, and reptiles. Two species that stand out are the Indigo snake and the Eastern Diamond-Back Rattlesnake. In places where this tortoise has locally disappeared so have certain invertebrates have also disappeared. It doesn't stop with just animals that dig burrows either. Other animals might be considered keystone species also. Let's look at one such creature.
The Beaver is one such animal that might be considered a keystone species. Beavers as we all know, gnaw down trees in order to feed and make their lodges and dams. It's this act of engineering that might just give the beaver it's status. Beaver dams provide new environments. They also provide predators places to hunt. These dams are a great place to look for aquatic animals. Reptiles like turtles and water snakes will be drawn to their waters for both shelter and for hunting purposes. The dam creates a place of fairly calm water where mosquitos can lay their eggs. According to the September 2009 issue of National Geographic magazine, the pond created by a beaver dam provides habitat for 7 species of bird, many species of insect, 12 species of fish, plants, small mammals, reptiles, and amphibians. Wipe out beaver lodges, and animals like Snapping turtles, Eastern garter snakes, Gray Foxes, and many others will be affected.
You may not realize this but an animal as cute as a sea otter is also a keystone species. It's disappearance in one area of kelp forest can case the forest of disappear. Why does it disappear? The kelp is grazed upon by Sea Urchins. Kelp is held to the bottom by the roots or holdfasts as they are often called. Once disconnected from the bottom, the kelp plant is at the mercy of the tide. Without the sea otter feeding on the sea urchin, their populations can explode which leads to the kelp forest getting smaller. Kelp forests provide shelter for prey and predators alike. If you would like to know more about this idea of keystone species, do your own little search. It's worth it.
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