What is the definition of an Invasive Species? An invasive species is defined legally in the USA as “An alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health…‘Alien species’ means, with respect to a particular ecosystem, any species…that is not native to that ecosystem.”
Invasive species are a major threat to our environment because they (1) can change habitats and alter ecosystem function and ecosystem services, (2) crowd out or replace native species, and (3) damage human activities, costing the economy millions of dollars. Invasive species rank second only to habitat destruction, such as deforestation, as a threat to biodiversity.
Almost half of the species in the United States that are at risk of extinction are endangered because of the effects of introduced species alone. In fact, introduced species are considered a greater threat to native biodiversity than pollution, harvest, and disease combined. Invasive predators can severely reduce the population sizes of native species, or even drive them extinct, because native prey species may not have evolved defenses against the novel predators.
There are several examples of introduced non-native species worldwide that should have sent up warning flags and the very clear message that these introductions should not be considered or condoned.
Invasive species are introduced on purpose (though that practice has been vehemently discouraged), or by accident. Let’s look at the Burmese Python as an example:
The Burmese Python Invasion
The Burmese Python is one of the five largest snakes in the world and are native to Southern and Southeast Asia. in their native habitat individuals average 12 feet (3.7 meters) long, but can reach 19 (5.74 meters) feet long. Burmese Pythons that were once pets either escaped or were released into the pristine environment of The Everglades National Park more than a dozen years ago.
The current estimated population of pythons in the Everglades is between 5,000 and 180,000, and they can be found in all areas of Everglades National Park, and have been observed north of the parks’ boundaries. They have no natural predators and eat amphibians, reptiles, birds, and mammals that vary in size from small rodents to deer, often feasting on rare and endangered species. They have now moved into populated areas and are feasting on our pets! Spectacular photographs of the snakes in struggles with native alligators have been released, directing international attention on the problem of invasive species in the Everglades.
The introduction of Canis Lupus Occidentalis
The Mackenzie Valley Wolf (Canis Lupus Occidentalis) was the subspecies used in the Yellowstone and Idaho introduction effort. Mackenzie Valley Wolves typically stand about 32–34 inches at the shoulder and males weigh between 100 and 175 pounds with unconfirmed reports of wolves weighing up to 230 pounds. The Mackenzie Valley Wolf’s thick, long limbs are proportionally built for traversing through rough terrain such as deep snow or the cliffy edges of the Rocky Mountains. Its deep chest hosts large lungs, letting the wolf breathe more efficiently at higher altitudes, and allowing it to exert huge amounts of stamina traveling up to 70 miles in one day.
While all species compete to survive, invasive species appear to have specific traits or specific combinations of traits that allow them to out-compete native species. In some cases the competition is about rates of growth and reproduction. In other cases species interact with each other more directly.
Common invasive species traits include:
High dispersal ability
I am sorry, but am I the only one infuriated by the fact that the US Fish and Wildlife Service did not fully understand that they were introducing a non-native species, and in doing so, they were not only setting our native wolves up for extinction, but they were setting these non-natives up to be hated and slaughtered? As angry as you may be at the hunters, should you not be even angrier at those who set these wolves up? The hunters that I know are hardworking decent citizens. They love their family, their pets, their livestock and their homes. They are hunters for reasons that are their own and they vehemently protect their rights to do so, and I respect them for that!