Thursday, September 11, 2008
Water impounded by dam #4 in the current Zealand valley system of beaver dams and ponds
This is beaver pond #4 impounded by the dam in the photograph below. It has 6 acres of surface area and holds a large quantity of water. From the human (hiker?) perspective the beaver dams and ponds in Zealand Valley are aesthetic as in this photo where the pond has created a large opening with a lovely view of Zeacliff in the distance which is further enhanced by the reflection in the pond. From an ecological point of view the ponds also have a positive impact locally as they create a rich habitat for a diverse interactive community of fauna and flora (animals and plants) than would not exist otherwise. The dams and ponds impact the types of plants that grow here and the animals that come in search of food. Ecologically we talk about 'Trophic Levels" or, more simply, "food webs" and "food chains". Beaver activity in total, not just the dams and ponds, significantly alters the local food web when they interact in the local ecosystem. Beavers themselves are in the middle trophic level meaning they are herbviores and only eat plants (vegetables), principally tree bark, aquatic plants and some non-aquatic plants like meadowsweet. Beavers stay close to home and engage in intense activity in a relatively small area. They expend a great deal of energy to procure and move their food and therefore need a lot of food proportionately and compared, say, to a mouse, or a chipmunk. Beavers signficantly alter their habitat by cutting down trees and slowing the flow of water and expanding water outwards into ponds that then floods plant communities sometimes destructively. In most cases this increase in activity and expenditure of energy is profitable for other animals and plants. The relationship between beavers and the trees they eat is an example of a food chain. It's a simple, direct relationship. The ecosystem the beaver dams and ponds make, however, gives rise to a complex food web involving plants (primary trophic level) and herbivores that eat the plants, like deer, porcupines, moose, fish or insects, and small carnivores, like birds, snakes, frogs, toads (yuck!) and spiders, that eat the small fish and insects, and the larger carnivores and omnivores that eat the deer, birds, and more of the plants and the fish like bears, fishers, mink, otters, coyotes, skunks, fox, and raccoons (to name some).