Ribbons of Life
A river begins as a trickle and ends in the ocean, but during its journey it creates a wide ribbon of habitat for animals. It's easy to think of a river as merely the water flowing between its banks, but a river is also deep pools, shallow riffles, sycamores, mud banks, plants and fish.Because of the connections between the river, the land and the species that depend on the river environment, it is difficult to point to an exact place where the river begins.
If the animals that depend on rivers and streams could tell us about their river homes, each would describe a different place. Catfish would tell about deep pools and tangles of roots. Kingfishers would chatter about the high cut-banks and shallow areas. Wood ducks would point out the mature sycamore trees along the water's edge. Herons would point to the endless backwaters, filled with frogs and crayfish.
Of course, rivers start with water. To catfish, that's all the river is. They spend their entire lives in the water, using their gills to absorb oxygen from it and their sensitive whiskers to find food in its dark depths.
Softshells live in the water right along with the catfish. Their webbed feet make them fast swimmers, and a periscopelike nose allows them to breath while the rest of their body remains submerged beneath the surface.
Softshells need more than water, however. When it is time to lay eggs, female turtles crawl out of the water onto a sunny sand bar. The turtle digs a nest, deposits eggs and leaves them to incubate in the warmth of the sun. When new hatchlings emerge weeks later they head for the safety of the water.
A sandbar is an essential part of the life history of this aquatic turtle and, therefore, part of the river. They could not live in a river without sand bars.
Tall mud banks stand high above the sand bar. An eroding section of the bank reveals layers of sand, soil and gravel. Some layers are thick, some thin. Each layer is a clue that the rising waters of the river claim this area frequently. Some animals make their homes here and depend on the changing river for their survival.
Just under the lip of a cut bank the kingfisher digs a tunnel into the soil, a temporary cavern that becomes a snug place to lay eggs and raise young. The warm sand provides a safe place to incubate eggs. The adult birds don't abandon the nest as turtles do, but tend it carefully until the young are ready to leave.
As you might guess, timing is everything. Kingfishers have to wait until after spring floods to start nesting, but the young birds have to be fledged before the water rises again. Kingfishers nest in river banks and fish the nearby waters for food. Kingfishers are part of the river, but without the high mud banks there would be no home for them.
Sycamore trees cling to the banks of the river, their leaves shading the waters below. During spring floods, the tangled roots and sturdy trunks of sycamores slow down and direct the water's flow. Herons and eagles perch in the large branches, and raccoons, otters and wood ducks find homes in the hollows of mature trees.
When these old trees get washed into the river, those same hollows become homes to catfish. Though we plant sycamore trees in lawns and along city streets, their rightful place is along the river. Many animals that live in our rivers and streams need sycamores.
Beyond the sycamore trees we find the river floodplain, which supports a diversity of fish and wildlife. Life in a floodplain is influenced by dramatic changes in water levels at various times throughout the year. Few species, plant or animal, have adapted to full-time living here.
Many floodplain inhabitants are highly mobile animals. Deer, for example, grow strong and healthy along rivers and streams, where they find plenty of food and cover and a reliable source of water. Although they can swim, they have no special adaptation to living in a floodplain beyond the ability to leave it when necessary.
Many species of birds live in bottomland forests. Red-shouldered hawks soar over the bottomland forest and nest in high branches. Chickadees and cerulean warblers forage high in the leaves of tall trees. Pileated woodpeckers hunt for insects in dead and dying branches in the forest canopy. Many birds depend on the floodplain, but most are ready to leave when the water gets high.
Beavers are clearly not aquatic, but everything about them, from their thick well-oiled fur to webbed toes, allows them to live successfully in rivers and streams. Beavers depend on the plants and trees growing in river floodplains, stripping the bark and eating leaves and buds from the trees they dropped into the water. Beavers are excellent swimmers who engineer dams that assure a minimal level of water all year long. And they build flood-prone homes.
Beavers make low, solid dams to withstand inevitable floods. When the river floods, the water tops the dam and spreads out over the floodplain. When flood waters recede the beaver colony immediately tends to repairs. Their entire life history is one of adaptation to the changing river.
Successful floodplain living is not limited to mammals, birds or even to vertebrates. The brown fishing spider lives along many rivers and streams. At night they wait on the surface of the water to feed on insects and small fish. They catch fish as effectively as the yellow and black spider in your garden catches grasshoppers.
This is one of the largest members of the wolf spider group. The legs of a fully grown brown fishing spider can appear as large as your outstretched hand. Fishing spiders are prepared to ride the rising waters as the river comes up and goes back down. Fishing spiders and the fish they eat are also part of the river.
Rivers are unpredictable and constantly changing. Sometimes they run placidly along, and sometimes they rage and flood, killing the animals and plants that depend on them.
Silver maples, cottonwood and willows tolerate frequent flooding, bald cypress can even thrive in saturated soils, but blackberries, locusts, pines and walnuts suffocate when high water levels prevent them from bringing oxygen to their roots. We lost a lot of these species during the floods of 1993 and 1995 because they are not designed to be permanent residents of the floodplain.
Annual and some perennial plants are not as seriously affected. They die off when the water is high, but reestablish themselves when water conditions are not threatening.
Low water also threatens the creatures that depend on the river. When river levels drop, fish are often cut off from the main flow. Trapped in evaporating overflow waters, they are doomed. Too little water can be as dangerous as too much water.
Standing knee-deep in an Ozark stream on a warm September day, there seems little doubt where the river is. You feel its pressure on your legs, you hear it lapping against the bank. But look around you and see the sandbars marked with animal tracks, the cut banks dotted with animal nests, the water-loving trees that attract countless birds and the thick growth on the floodplains that stretch to the bluffs. You realize that flowing water is only a small part of the river's ribbon of life.