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Meadows in Mist

It is always magical to walk into a meadow. Maybe it is the vigor of new life that seems to pull on all the strings of your soul. After all, meadows seem to elicit a feeling of rebirth, being dominated by various assemblages of early successional vegetation in the form of grasses and sedges. A meadow may persist in an arrested successsional state, or a meadow may be a temporary sere. Meadows form where lakes or ponds are drained, lands are grazed, fire is periodic, soils are poor, or beaver dams are abandoned. They are lands once rich in forest diversity that were altered naturally or, more often, by humans.

Beaver meadows can be the most aesthetically pleasing and, in my opinion, the most valuable of all meadow types, if only from the standpoint of how they are created and what they develop into. As spring approaches and the promise of new growth abounds, it is fitting to take a moment to reflect on Earth's most prestigious engineer, the beaver (Castor canadensis). No other mammal alters the shape of the landscape and is as opportunistic, excluding humans. Beavers truly define the term "keystone species," having once covered a tenth of the continental United States with beaver-built wetlands. Since wetlands spread behind their dams, beavers provide homes for hundreds of species, including billions of phytoplankton and zooplankton, myriads of insects, frogs, fish, migrating waterfowl, moose, and great blue herons.

Beaver legends have been a part of human culture from the time of pictographs. Cherokee and other eastern tribes shared stories of how the Great Spirit directed the beaver to dive to the bottom of the water-covered earth and carry mud to the surface to form dry land. Flathead Indians believed that beavers were disgraced Indians, changed from their human form by the Great Spirit. Beavers worked cutting trees and building dams and lodges as atonement for their misdeeds.

In North America, a 7-foot-long giant beaver, Castroides, once graced the waterways. While not a direct ancestor of the modern beaver, Castroides did coexist with Castor until 10,000 years ago and is believed to have been even more specific to water, minimizing the effort spent moving such bulk on land and avoiding predators. Castroides demonstrated the effectiveness of a beaver's life strategy by sheer size, while Castor demonstrated the effectiveness of such a life strategy by sheer numbers. It has been estimated that 200 million beavers once inhabited the continental United States alone. Beavers cloaked the landscape from the Artic Circle to the Gulf of Mexico and from the southwest desert to the north woods of Maine, with water and trees the only constants.

A beaver that hears the sound of running water will immediately try to locate the source and to dam it, if at all possible. Beavers make dams to raise the water level of a stream and to maintain this level during dry periods. Beavers will dig canals, plunge holes, underwater aqueducts, and channels throughout their pond and wetland, creating a safe passage from their home to their food.

Beavers are natural farmers, using nature's system of replenishment to prosper until the time comes to move on. Their primary fall and winter food is tree cambium, and favorite trees include aspens, cottonwoods, and willows, which are all pioneer species that readily colonize logged, flooded, burned, and riparian areas where sunlight is plentiful. As beaver dams slow the water, soil and nutrients from upstream drop out of the water column. Soon natural herbs, such as cattails, arrowhead, pondweed, smartweed, milfoil, pond lily, and a variety of sedges and grasses begin to flourish. Beavers can feed on this higher energy food source in spring and summer, without having to venture far from the safety of water.

Wetlands act as enormous biological filters. When muddy water from streams and rivers rush into the stillness of the wetland and stream velocity diminishes, silt in the water adheres to aquatic vegetation, and larger particles settle to the bottom. Species in the wetland's underwater world, including planktonic bacteria, freshwater fungus, and phytoplankton, use organic and inorganic molecules, including human-developed pollutants, to survive, creating the base of a complex food web. Zooplankton, such as protozoans, rotifers, and tiny crustaceans (Daphnia), graze on the phytoplankton. Backswimmers, striders, water boatmen, diving beetles, water scorpions, coiled mosquito larva, mayfly larva, dragonfly larva, and many other insects eat the grazers and together act as the food source for amphibians, fish, and birds.

Beaver-created wetlands clarify water, prevent soil from washing downstream and fashion fertile meadows with a rich blanket of organic matter. On a grander scale, detained water is more likely to percolate down to the groundwater, raising the water table and creating springs and freshets throughout the watershed. Once the dams are gone, land quickly reverts back to a forest, but now with added nutrients that enhance both richness and diversity. Fungal connections are still intact, and intricate soil relationships have progressed.

Ecologically, one could speak of a wetland as an ecotone, a transition between two distinct communities. An ecotone provides niches for organisms associated with both communities, as well as niches unique to the ecotone. This "edge effect," where there is increased variety and density at community junctions, makes wetlands so productive. Beavers increase the expanse of the edge between waterways and dry land, dramatically increasing the acreage and quality of this productive ecotone. When trapping eliminated almost all the beaver in North America, we in effect lost 300,000 square miles of wetland.

We will never see beavers in the numbers they once obtained on this continent. In their peak there were more than 25 subspecies from coast to coast, mainly due to geographic isolation. Castor canadensis canadensis, was the "typical beaver," inhabiting almost all of the forested area of Canada. Castor canadensis michiganensis inhabited the Great Lakes region, and had the darkest, most valuable fur. Castor canadensis subauratus, the golden beaver, inhabited Central California. Today, we cannot differentiate subspecies. Most present populations are products of reintroduction efforts. All geographic variances have been lost.

Clean water is a leading concern for all life. In order to promote healthy waterways, it seems prudent for all citizens to have a general understanding of what once made North America's water so pristine. Knowledge of beavers and the wetlands they create can only aid us in our quest to develop in a more ecologically sound manner. Imagine if we worked with a "natural common sense" how much richer all of our lives would be.