Invasive Species, Growing Seasons, Life Cycles & Global Warming

Invasive species in North America include the Burmese python, the snakehead (a carnivorous fish capable of walking across land a.k.a frankenfish), the zebra mussel, gobies and mile-a-minute weed.

By definition, "invasive species" are "an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health" (U.S. Executive Order 13112). It is estimated that invasive species cost $137 billion per year according to a 1999 Cornell University Study.

Invasive Plants: America's Most NOT Wanted

While weeds and pests in the garden can be frustrating and time consuming to control, in nature invasive species can wreak havoc.

By definition, an "invasive" species is a non-native plant, animal or other organism that, once introduced into a new environment, out-competes native species for habitat and food. Although not all exotic species are invasive, those that are can cause tremendous problems.

Particularly troubling is the fact that a number of non-native plants that people have brought into their gardens as ornamentals have turned out to be some of the most damaging species when introduced into natural habitats. With global warming, many of these species are expected to gain even more of a foothold.

Invasive Species

Since earliest times, humans have deliberately or inadvertently moved organisms from one place to another. Most of our food and forestry crops and domesticated animals, for example, are introduced species, cultivated far beyond their normal ranges. In recent years, though, the rate of such translocations has increased dramatically because of greater movement of the human population, providing numerous new pathways for unintended movement of organisms.

Not all introduced species are able to spread successfully and become invasive; most quickly succumb in their new environments. However, when species are introduced into environments free of the diseases and predators they faced in their native habitat, or when species grow and reproduce more rapidly than similar organisms in their new habitat, they may pose a significant threat to local ecosystem functions and biodiversity or even cause harm to human health. Their economic impact can be substantial; it reaches billions of dollars each year in the United States alone.

This Tracer Bullet lists selected books and other resources related to the many aspects of invasive species. Not intended to be a comprehensive bibliography, it is intended–as the name of the series implies–to put the reader “on target.”

Wetlands and Invasive Plants in a Warming World

They're out there. Little by little, a silent invasion is sweeping across the northeast landscape, and the rest of the world for that matter. An oft overlooked but devastating ecological crisis: invasive, exotic plants are exacting a toll on New England's array of forests, fields, and wetlands.

The invaders – released outside their native lands, notably Europe and Asia – got their foothold here in the early 19th century. At that time, Americans were embracing plants from across the globe for both ornamental and agricultural purposes. Now infamous for escaping their garden boundaries, the ecological havoc wrought by these plants on our natural systems is well documented. Free from the insect and disease predators of their native countries, invasive plants can easily out-compete and displace entire native plant communities.

Let's keep in mind why plants are crucial to life on earth. They are the only organisms capable of capturing the sun's energy and, through photosynthesis, converting that energy into food for animals, including us. Insects play a critical role in food webs by consuming native plants, and in doing so, transferring the energy otherwise locked in plants to other animals (for example, birds and frogs) that prey upon them.

Most native insects cannot or will not eat invasive plants. When native plants are crowded out by invasives, insects -- including many that are beneficial to people -- are deprived of essential food sources, ultimately leading to a weakened food chain. As native vegetation and native wildlife are inextricably linked, what was once a healthy, tightly integrated assemblage of native plants and wildlife begins to unravel.

What, then, does the specter of plant invasions have to do with wetlands and global warming? Plenty. While much attention has been brought to anticipated sea level rise and increased frequency and intensity of storms due to climate change – all of which adversely impact coastal wetlands – much uncertainty remains about the fate of our inland marshes and swamps in the face of rising temperatures.

At least one variable seems a little more predictable, however: USDA plant scientists are finding that increased levels of atmospheric carbon dioxide (a primary driver of climate change) appear to favor the growth of some invasive plants over their native counterparts. If such observations hold true, we could witness an even more dramatic expansion of non-native plants blanketing our most coveted open spaces, especially wetlands.

By 2050 Warming to Doom Million Species, Study Says

By 2050, rising temperatures exacerbated by human-induced belches of carbon dioxide and other greenhouse gases could send more than a million of Earth's land-dwelling plants and animals down the road to extinction, according to a recent study.

"Climate change now represents at least as great a threat to the number of species surviving on Earth as habitat- destruction and modification," said Chris Thomas, a conservation biologist at the University of Leeds in the United Kingdom.

According to the researchers' collective results, the predicted range of climate change by 2050 will place 15 to 35 percent of the 1,103 species studied at risk of extinction. The numbers are expected to hold up when extrapolated globally, potentially dooming more than a million species.

As global warming interacts with other factors such as habitat-destruction, invasive species, and the build up of carbon dioxide in the landscape, the risk of extinction increases even further, they say.