Cats are killing the everglades. The biggest wetlands in America are being threatened by colonies of feral cats. To understand why, I tried to conduct a (somewhat professional) study of what makes a wetlands work.
The idea of wetlands holds a special place in our collective unconscious. The bogs, swamps and marshes of our imagination are home to dark and mysterious life. They are the natural world’s embalmers, places of death and decay—biologically rich yet terrifyingly shadowy.
The word ‘swamp’ has come to mean ‘overwhelming’. We talk about being swamped with information, about events swamping the media. The word has come to evoke the all-encompassing sticky muck that we cannot get off our hands.
In real life however, swamps, marshes, wetlands in general, are beautiful. Instead of being hostile and morbid, these buffer zones between land and water are tranquil and teeming with life.
The United States has four distinct wetlands areas, roughly corresponding to the four basic geographical regions. The brackish marshes of the northeast are worlds apart from the swamps and bogs of Florida and Louisiana. The common thread that links these wet worlds is something called carbon productivity.
In the Audubon Society Nature Guide for wetlands, William A. Niering explains why wetlands are among the most productive ecosystems in the world.
The high productivity of wetlands is due to their ability to capture large amount of the sun’s energy and store it as chemical energy, as well as to their efficient recycling of that which is produced. The rate at which photosynthesis produces energy or stores sugars in plants is the rate of primary productivity. The total amount actually produced by an organism in a given time is referred to as its gross productivity. Some of this energy is used to maintain the organisms life processes; the stored energy that remains is net productivity.
Niering goes on to explain that the particularly high productivity in wetlands comes in large part from the ‘pulsing’ of the water level. The slow rise and fall bring in new nutrients and subsequently make them more accessible. New water also keeps the entire ecosystem more oxygenated. Frequent flooding enriches the water with oxygen and provides more productivity than stagnant water.
Because of such an enormous level of productivity, the diversity of life that can be supported in a wetlands environment is unmatched in this country. In the Florida Everglades alone, six distinct ecosystems thrive. The sawgrass plains surrounding lake Okeechobee are home to radically different plants than the mangrove forests in the brackish waters of the south. The water’s transition from fresh to brackish to salty is reflected in the life supported.
Which is why it’s all the more alarming to think back to the mid 1880s, when the swamp wetland acts were passed by congress. These acts gave 65 million acres of federal land to 15 states. The purpose was so that the land could be ‘reclaimed’—wetlands were drained in order to be used for more ‘constructive’ purposes.
The transition zones that provide such a biologically rich home are also the reason wetlands are among the most delicate of ecosystems—they are easy to destroy. The 215 million acres of wetlands that existed in the continental US when the Europeans arrived have been willowed down to less than half their original size—only 99 million acres of wetlands remain in the US today.
Wetlands work the way they do because they huge transition zones between wet and dry. Their lowness and flatness makes nutrients easy to access, which allows a very high plant density and, in turn, a lot of food for other things to eat. The food chain is long in the wetlands. So when a high biodiversity is dependent on such a specific set of conditions—salinity, water level, surrounding symbiotic life—it’s incredibly easy to disrupt the delicate balance.
The Everglades are suffering right now. Besides the edging in being done by the humans that surround the glades, invasive species are ripping through the 4000 square mile wetlands.
Because invasive species have no natural predators in their new home and there are no natural controls to prevent their growth, their effect doubles. Things that shouldn’t be there are, and things that should be there are diminished due to the rampant growth of the invaders.
Burmese pythons are battling alligators. Brazilian climbing ferns are providing fire ladders up tree trunks. Walking catfish destroy fish stocks and the hydrilla plant clogs waterways, blocking sunlight and lowering oxygen levels in the water below.
But the creature causing the most damage is not an exotic reptile, bizarre plant or freaky Thai fish. It’s your friendly neighborhood tabby or slinking Siamese. Feral cats are the number one Everglade invader—an issue that has not gotten much media attention.
In a 2003 report to the U.S. Fish & Wildlife service, Pamela Jo Hatley, from the University of Florida Conservation Clinic, reported that “the number of owned and feral cats, combined, that are outdoors and potentially preying on wildlife in Florida is in the neighborhood of 12.5 to 15.8 million.”
Cats are natural predators. A kitten playing with a string is merely imitating what it would do to a tiny creature in its death throes.
More than 350 distinct species of birds have been identified as living in the Everglades, both as permanent residents and migrators. Wading birds, land birds, and birds of prey use the glades as a one stop shopping center for everything delicious and nutritious. As the biggest non-reptiles in the wetlands, they’re natural predators are slim to none. It’s not easy for a mammal to kill an animal soaring through the sky. But some animals are engineered to hunt exactly this type of creature, and those animals are not supposed to be in the southern florida wetlands.
The Everglades National Park website notes that “invasive exotics are the primary cause of species endgngerment and have contributed to 68 percent of extinctions in the US.”
The saddest part of the issue is that it’s not something that is impossible to control. Old world climbing ferns might never be stopped. Idiot kids are not going to stop dumping Burmese Pythons in the waters outside their house. But all we need to do to stop cats from ravaging the unique species of migratory birds is KEEP THEM INSIDE. And the cats that already roam alone outside, eating and reproducing and roving in packs, need to be colonized, treated, or humanely put down. It sounds horrible but its not that expensive and it’s a much smaller price to pay than to destroy the homes of dozens of migratory bird species.
The health of the wetlands is not dependent on a single factor. It’s a network of life with each aspect supporting another. It’s a beautiful, still, captivating place. I hope that we don’t end up merely ‘remembering’ what the Everglades ‘were like’.
I leave you with Sidney Lanier’s poem The Marshes of Glynn, which immortalizes the beauty of the wetlands in his native Georgia.
The creeks overflow: a thousand rivulets run
‘Twixt the roots of the sod, the blades of the marshgrass stir;
Passeth a hurrying sound of wings that westward whirr;
Passeth, and all is still; and the currents cease to run;
And the sun and the marsh are one.
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