There are places in the Everglades where the landscape seems alive, rippling with movement, raucous with sound. Reptiles, amphibians, mammals and birds fill the grasses, trees, sloughs, and sky above. The vast majority -- egrets and cranes, frogs and toads, alligators and crocodiles and hundreds of other species -- are native, natural components of the ecosystems.
But there are more than a few that are invaders, non-natives that arrived in one mode or another. Though the majority of these are relatively innocent, with little direct impact on the surrounding environment or their newfound neighbors, one in particular is having an impact far more extensive than a rippling in the grass.
As a report out this week testifies, the constricting python is a potent predator, a quick-growing mass of muscle that is a threat to anything that moves in the Everglades. Its reach is far and its appetite large, with scientists telling us that populations of small mammals -- raccoons, opossums, even bobcats -- are being wiped out of some parts of the national park by these slithering predators. But its prey also can be much, much larger.
Snake-eating alligators and alligator-eating snakes might seem like a science fiction story-line, but those battles are playing out in Everglades National Park, where the invasion of non-native pythons threatens to upend a rich and diverse ecosystem that includes the largest tract of wilderness east of the Rockies. Larry Perez skillfully explores this astonishing assault -- the repercussions already tallied and those lying in wait -- in a book that reads almost like fiction but which, sadly, is only too factual.
In Snake in the Grass: An Everglades Invasion, Mr. Perez takes us into the green leafy realm of Everglades National Park not in pursuit of the python, but rather in its wake. And it is a wide wake at that.
“Regardless of where they are found, these pythons normally utilize the full gamut of natural features in an area, frequenting burrows, trees, rocky outcrops, riparian zones, open water, and disturbed lands. In doing so, the snakes exercise their astonishing ability to swim, climb, and contort their bodies to meet the demands of the landscape. They are aided, of course, by tools forged over time through evolution: a supple skeleton, sinewy layers of muscle, and strong prehensile tails.”
The details of the invasion, presented through the eyes of a long-time naturalist who has spent his career working in many of south Florida's protected landscapes, are enthralling, and greatly concerning. Though this book, which is available March 1, revolves around the Everglades, it is emblematic of a problem not isolated in south Florida. Asian carp are making their way north up the Chicago and Illinois rivers towards Lake Michigan, and round goby already have infiltrated all of the Great Lakes. In Yellowstone National Park, non-native lake trout first detected in Yellowstone Lake back in the 1990s today are a great threat to the native, and smaller, cutthroat trout.
But unlike Yellowstone Lake, which is largely a closed system for the lake trout, the River of Grass is an unfenced wilderness setting that the pythons seem to find to be an ideal home. There is more than ample food, as this week's report in Proceedings of the National Academy of Sciences makes abundantly clear. Burmese pythons, the USGS notes in discussing the report, are responsible for a "a nearly complete disappearance of raccoons, rabbits and opossums ... in the remote southernmost regions of the park, where pythons have been established the longest. In this area, populations of raccoons dropped 99.3 percent, opossums 98.9 percent and bobcats 87.5 percent. Marsh and cottontail rabbits, as well as foxes, were not seen at all."
Mr. Perez helps frame this ecological calamity for us.
He touches on the debate over how the snakes got into the grass in the first place: "Though accidental importation has clearly resulted in the introduction of numerous harmful species, the deliberate importation of wildlife has greatly exacerbated the problem through the egregious release of many more. One study of introduced reptiles and amphibians in south Florida revealed that approximately 56 percent of established species resulted from releases by animal dealers or purchasers."
But, more importantly, he sorts through the ecological threats the snakes pose to the River of Grass and its natives, threats now playing out, and to the threat in general of non-native species in the Everglades and elsewhere in the world.
Upheaval of the Everglades ecosystem as the snakes multiply, grow to a size that enables them to kill and swallow even 6-foot-long alligators, spread out across the landscape, and dine on the natives is just the most obvious outcome. Lurking in the background, though, is the potential for human injuries or deaths, a point Mr. Perez makes by citing a 2009 case in which a toddler in Sumter County in central Florida was killed by a "pet" python that escaped its terrarium.
More killer snake stories play out over the ensuing pages, from southern Africa, from Indonesia, from New Jersey, from Pennsylvania, and other locations.
It is generally understood that grizzly bears kill hikers in Yellowstone National Park, that black bears kill hikers in Great Smoky Mountains National Park, and, now, that even mountain goats kill hikers, in Olympic National Park. With an ability to attack quickly, silently, and powerfully, might one day a python kill someone in the Everglades?
How to get a grip on the Everglades' python problem appears to be a monumental problem. While there have been pleas to park officials from hunters and collectors for permission to venture into the Everglades to capture the snakes and theorectically blunt their spread, Mr. Perez notes how difficult that would be.
"Armed with earth-tone coloration and a penchant for submersion, the animals seemed perfectly suited for a life of hidden seclusion in the Everglades. Most days, one would have had a better chance of finding the Skunk Ape -- the foul-smelling cousin of Big Foot that a handful of locals claim haunts the 'Glades. Even armed with expensive transmitters and years of field experience, researchers repeatedly encountered great difficulty visually locating their subjects thanks to a complete lack of contrast between patterned reptilian skin against a busy background of vegetation."
Snake in the Grass, though, is a story about more than pythons slithering through the Everglades. It is also about society's penchant for collecting the unusual, the powerful, the exotic, and the problems those collections can cause. Burmese pythons are just one non-native species seemingly well at home in and around the Everglades, notes Mr. Perez. Others include African five-lined skinks, carnivorous Nile Monitors, 2-foot-long Oustalet's chameleons, and 4-foot-long black-and-white tegus, a type of lizard happy to eat birds, amphibians, insects, even fruits.
The dilemma these cases hold out to us is that as the world becomes a smaller place, as more people choose to bottle up nature in terrariums, aquariums, and other containments to admire, the risks grow that somehow, some way, these creatures not native to our backyards will gain their freedom and redraw the norms of natural biodiversity.
In short, writes Mr. Perez, "...are we to favor greater global diversity -- which is likely to be experienced and appreciated by the few -- over greater regional diversity that would be enjoyed by so many more? That far-flung regions of the earth are now being seeded with an identical stock of hardy organisms has long been an argument for the prevention of introductions."
Unfortunately, for the Everglades, where the first Burmese python, a 12-footer, was spotted in 1979, it appears to be a little late for that argument.
"For Burmese pythons in the Everglades, the writing is clear upon the palace wall," writes Mr. Perez. "Observers have long since resigned themselves to the realization they will continue to infest south Florida into the foreseeable future, requiring costly amounts of time and money in a bid for limited management. Nonetheless, it has also been hoped that the high-profile disaster unfolding in the Everglades would provide sufficient cause to prevent similar introductions in the future."
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