Everglades National Park - Flood and Famine
In the Everglades, the amount of water waxes and wanes with the seasons. Announced by spring rains, the wet season persists through summer, with fierce thunderstorms that roll across the landscape. Saw grass and hammocks alike gleam wetly in the late afternoon sun, and dry muds turn squishy as the river of grass begins its annual flow.
As if the rain-generated current were a signal, cypress trees, their leafless branches draped with shawls of Spanish moss, begin sprouting fresh green needlelike leaves; unusual for conifers, the leaves of these trees turn color in autumn and drop off, as do those of maples and other broad-leaved trees. Cypresses are members of the same family as the redwood, and like their California kin, some grow very tall. The bald cypress, for instance, towers more than a hundred feet above the riverbanks: in urban terms, one might call it the skyscraper of the swamp. In contrast, the aptly named dwarf cypress is only three or four feet tall.
Mosquitofish reproduce explosively to celebrate the spring and the coming of the rainy season. These rather drab little minnows, named for the food they eat, spread across the prairie so swiftly that farmers used to swear that minnows were raining down from heaven when they say newly formed puddles filling up with mosquitofish. Other fish, such as bluegills, bass, and gars, soon leave their dry-season refuges and spread through the park -- and the larger wildlife that feeds on them does the same. A good year for fish means a good year for herons, egrets, and other wading birds.
The rains culminate in gigantic midsummer downpours and sometimes in hurricanes that flatten the saw grass, turning the landscape gray and malevolent. Finally the storms subside. The land starts drying up, and by late autumn the Payahokee is reduced to a trickle. By midwinter the flow may come to a halt and the water evaporate completely, leaving only puddles in the depressions. Some years are so dry the mud cracks, the land becomes parched, and the algae turn to wispy white dust.
Then alligators move out over the exposed and pitted limestone, seeking large holes filled with mud and the last of the water. Churning their bodies back and forth, the alligators shove the mud out with their blunt snouts and powerful tails, and the excavation fills slowly with water seeping in from underground. Here the alligators stay, the water a relief from the hot sun beating on their leathery black hides. The water holes created by the alligators become the swamp's salvation. Turtles, snakes, frogs, wading birds, raccoons, otters -- an incredible variety of wildlife seeks out their cooling, life-giving waters.
As the sun beats down, fish may die by the millions, their skeletons rimming the shrinking pond. Gars -- long-snouted, long-bodied -- hold out longer than most, since the swim bladder acts as a lung and allows them to survive in warm, oxygen-depleted water by gulping air. Mosquitofish, too, can outlive others; their upturned mouths and flattened heads enable them to skim air from the thin film on the water's surface, where the amount of oxygen is highest.
Incredible as it may seem, the dry season encourages new life. Wading birds will mate only when food is plentiful at the proper time of year. Too much water, and mating does not occur, because the fish on which they depend are so spread out that the birds fail to congregate at the small holes. Too little water for too long, and the fish perish; then such birds as wood storks and herons refuse to breed.
But if the ponds and water holes are full, wood storks will walk slowly around the depressions, shuffling through the mud and stirring up hordes of wriggling fish. Wood storks hunt by touch, groping in the mud with their 10-inch-long bills. When the bill makes contact with a fish or with other prey, it snaps shut by reflex action, which is quick indeed: it takes a mere twenty-five thousandth of a second.
When disturbed, these black and white birds, the only storks native to North America, clack loudly and take to the air with difficulty -- but once airborne they become the quintessence of grace. Their wings span an impressive five feet. Riding currents high in the sky, they may travel 40 miles a day in search of a well-stocked hole.