The distribution of Pomacea insularum in South Florida
“Here are no lofty peaks seeking the sky, no mighty glaciers or rushing streams wearing away the uplifted land. Here is land, tranquil in its quiet beauty, serving not as the source of water, but as the receiver of it. To its natural abundance, we owe the spectacular plant and animal life that distinguishes this place from all others in our country.” President Harry S. Truman dedicating Everglades National Park on December 6, 1947
Half of the original, vast, tropical wetland, called the “Everglades,” has been developed for agriculture and residences in burgeoning South Florida. Much of the remainder is subject the destructive forces so common to Florida’s water bodies – – nutrient pollution, disruption of the natural hydrology, and introduction of exotic species. That is why Congress approved a plan in 2000 to Save the Florida Everglades, the most ambitious environmental fix in U.S. history. As part of this program, President Obama signed legislation on March 11th that will provide $200M for work on the Tamiami Trail, restoration of the Kissimmee River, and reinforcement of the dike around Lake Okeechobee.
Earthmoving projects are important, but the long term survival of the native biodiversity of the Everglades will hinge on invasive species control. South Florida’s spectacular native plants and animals will stand or fall in their last, great bastion, the Everglades National Park (ENP), the largest wilderness area east of the Mississippi River. At 1,400,000 acres, the ENP is the third biggest national park in the “Lower 48” and has global distinction as an International Biosphere Reserve, a World Heritage Site, and a Wetland of international Importance.
Because of the close proximity to bustling ports importing ornamental plants and exotic pets, the ENP also has the misfortune of being home to 120 invasive plants, such as the Punktree (Melaleuca quinquenervia), Australian Pine (Casuarina equisetifolis),Old World Climbing Fern (Lygodium microphyllum), Brazilian Pepper (Schinus terebinthifolius), and 76 invasive animals, including the Burmese python (Python molurus bivittatus), the Monitor Lizard (Varanus spp.), the Spiketop Apple Snail (Pomacea diffusa), and the Island Apple Snail (Pomacea insularum).
While the native Florida Apple Snail (Pomacea paludosa) is an integral part of the Everglades ecosystem, the Island Apple Snail is an exotic interloper causing concern among National Park Service scientists. Will the expansion of this exotic apple snail cause the extirpation of the native apple snail? What effect would that have on other species, like the endangered Everglades Snail Kite (see Previous Post, Snail Kites in Trouble). Will the exotic snails grow in such large numbers that they damage the wetlands? Will they be vectors of diseases and parasites that could infect the native animals that inhabit the ENP?
In May 2005, I spoke with Skip Snow, Wildlife Biologist (ENP), shortly after the Island Apple Snails were discovered in the Old Tamiami Trail Canal just inside the park boundary. He and his co-workers were intent on executing an effective, rapid response. Park personnel immediately began conducting frequent, GPS surveys of the range of the Island Apple Snail while removing all the egg clusters and adults they could find. Though not exactly comparable, the results: 19 adults and 488 egg clusters were removed in 2005; 34 adults and 2857 egg clusters, in 2006; 17 adults and 1024 egg clusters, in 2007; and 52 adults and 508 egg clusters, in 2008. “Our surveys suggest the non-native apple snails are present only along the northern boundary of ENP.” The overall conclusion, however, is that “the P. insularum population within ENP appears to be expanding slowly” (Report by Kline & Fratto, September 30, 2008).
Yesterday, I spoke with Jeff Kline, Fisheries Biologist (ENP), and asked him how the battle with the Island Apple Snail was going, and he said, “It’s hard to say. There appeared to be a decrease in egg production, then the S-12 gates were opened and reproduction increased greatly. This may be a result of new snails moving in through the gates, or their egg laying may be cued by the environmental conditions of rising water levels or flow. At any rate, these results preliminary. Snails are just starting to lay eggs down here now. It going be interesting to see what happens in the next few months.” Yes, indeed. My hat is off to Skip Snow, Jeff Kline, Zach Fratto, and all the others fighting the exotic onslaught in the Florida Everglades in an effort to protect “the spectacular plant and animal life that distinguishes this place!” Posted by Jess Van Dyke
Natural Resource Management/ Island Apple Snail:
Everglades Cooperative Invasive Species Management Area: