Thursday, July 11, 2013

The invasion of the habitat snatchers

There are many challenges facing the environment around the country, indeed around the world, these days, but among the most deadly and seemingly intractable of these are the invasives.

Invasives are plants or animals from someplace else in the world that have been brought to our shores, sometimes deliberately, sometimes by accident, and released or escaped here. Often these plants or animals find a hospitable habitat with none of the natural enemies or controls which they encountered in their native land. The predictable result is that their population explodes. They compete with native species and sometimes overcome them, even wiping them out. They become habitat snatchers. 

In the island nation of New Zealand, for example, where non-native rats and stoats have become entrenched, they have been primarily responsible for the extirpation of at least 19 bird species.    

In the United States, one of the most famous invasives is the House Sparrow, which was deliberately introduced in New York in the 19th century. It quickly spread and began to compete with native hole-nesting birds like Eastern Bluebirds and Tree Sparrows, contributing to a decline in these as well as other species before human intervention began to give the natives a fighting chance.

In the 20th and 21st centuries, with the globalization of the economy and the ease of tourism between countries, the rate of introduction of invasives exploded. No state in the country has suffered more from this phenomenon than Florida where new invasives seem to be added to the list on an almost daily basis.

From walking catfish, Asian swamp eels, Cuban tree frogs, monkeys, iguanas, and, most famously, Burmese pythons, the state's ecology  is overrun by these outsiders that are making themselves right at home. Indeed, the pythons have been so successful in the Everglades that they have virtually wiped out the small mammal population there. This, of course, has disastrous and long-term effects on the native predators in the area that normally depend on these mammals for food.

Even the alligators there have had trouble holding their own against the pythons. Bodies of the native reptiles have been found in the stomachs of big pythons that have been captured and killed.

As if all of this were not enough, Florida is now battling another invasive - giant African land snails, sometimes called GALS. These snails can get up to 8 inches long. Each snail contains both male and female reproductive organs and every mated snail lays about 1200 eggs a year. As of June 22, Florida state officials reported that they had captured and killed more than 124,000 of the snails in the area around Miami.

These snails pose a major threat to gardens and to farmers' crops because they will feed on and destroy at least 500 different types of plants. But it's not just plants that they gobble. They will also chew on plaster and stucco, thus causing damage to homes. And, one other thing: They also carry a parasitic nematode that can lead to meningitis in humans. Unbelievably, these critters were deliberately  smuggled into the country by a religious cult which uses them in their "healing ritual."

Florida is fighting a war against its invasives with all available resources, but in all too many instances it seems to be losing the battle. But the battle may spread to other states.

There is always the chance that many of these species will be able to spread to other hospitable habitats, especially in adjoining states along the Gulf of Mexico. And as the climate changes, becoming warmer, the possibility of some of the species being able to even move into other areas of  the country only increases.

The temperature of the planet continues to rise with nine out of the ten hottest years on record having occurred in this century. Moreover, three out of those hottest years have been within the past five years, so we can't depend on a hostile climate to be a barrier to the invasives.  

All of this, the invasive plants and animals plus the warming climate, could prove to be devastating for our native plants and animals. The decimation of species which Florida has experienced could become more widespread. It is a nightmare scenario, one that desperately needs a solution but for which no real workable solution seems in sight.

(An earlier version of this was posted at Backyard Birder and Gardening With Nature.)

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