Introduction
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
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
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
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
"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.
Examples of Invasive Species and Global Warming's Effects on Life Cycles
Climate change changes the climate. What effects does the change in climate
have upon life? Plants, animals and insects are impacted in a variety of ways.
As the globe warms, growing seasons my be extended further north in the northern hemisphere
and further south in the southern hemisphere. This allows some plants to migrate and flourish while
it kills other plants. The same holds true for certain species of animals and insects.
For instance, it reduces the hibernation period for some snakes. It has also been shown
to extend the range of the cuckoo wasp. The cuckoo wasp is a parasite that kills native bees.
While weeds and pests in the garden can be frustrating and time consuming to control, in nature invasive species
can wreak havoc.
-- National Wildlife Federation
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.
-- US Library of Congress
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.
-- Environmental Protection Agency (2008)
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.
-- National Geographic (2004)
Gypsy moth caterpillars, ailanthus and colonizing earthworms are killing trees.
The cuckoo wasp
has pushed north and kills native bees.
The eastern ribbon snake's reduced hibernation.