All the plants and animals native to an ecosystem — whether it is a forest, swamp, desert, marsh or other natural environment — play a role in keeping the system healthy and intact.
Some species, though, are especially crucial. If they become scarce or are entirely removed from an ecosystem, the system dramatically changes and may even collapse.
Such species are known as “keystone species” because, without them, all other species in an ecosystem may be adversely affected. Some may disappear or even become extinct.
Some of Georgia’s keystone species include:
- Beavers, whose dams create ponds that allow many other creatures — fish, frogs, turtles and others — to flourish. Beaver dams also stimulate the growth of several plant species that songbirds use for food, shelter and nesting. Without beaver dams, songbird diversity declines in an area.
- American alligators, which use their tails to dig holes that hold water during dry spells. "Gator holes" are often critical to the survival of a number of species because the holes may be their only water source during a drought.
- Gopher tortoises, native to Georgia's sandhills. The large underground burrows that they build also are used by more than 350 species, including owls, snakes and frogs. The endangered indigo snake is especially dependent on the burrows.
- American oysters, whose large coastal reefs provide homes and shelter to scores of other marine species, including fish, crabs, plants and invertebrates. Oysters clean the water, recycle nutrients and help regulate energy flow, vital functions for keeping salt marshes and estuaries healthy.
- Yellow-bellied sapsuckers, which are "winter only" birds in Georgia. The "sap wells" they drill into hardwood trees benefit many other species, which feed either directly on the sap or on insects attracted to it.
- Red cockaded woodpeckers, an endangered species. The deep nest cavities that they drill in mature pine trees are, when abandoned, used by numerous other native species of Georgia's pinelands.
In the sky: The moon will be last quarter on Wednesday, said David Dundee, a Tellus Science Museum astronomer. Mars is low in the southwest at sunset and sets a few hours later. Jupiter rises out of the east a few hours after midnight and will appear close to the moon on Friday night. Saturn is very low in the southwest just after dark. Mercury and Venus are too close to the sun for easy observation.
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