Overview
Each species evolves in the presence of others and develops a natural
pattern of relationships with these other species – as competitors,
predators, disease organisms, and so on. Most often species are also
limited by physical or other barriers. For example, land is a barrier
to the spread of aquatic species just as water can be a barrier to
the spread of many land animals. Within these barriers, natural systems
(ecosystems) begin to form.
Over geologic time, the world’s major ecosystems developed
their own unique assemblages of plants and animals - each accustomed
from millennia of adaptation to the others presence. There is always
some exchange within and among ecosystems – but humans have
dramatically altered this picture by moving species, on purpose or
by accident, all over the globe at an unprecedented rate.
Species that evolved in one place are referred to as being “native”
to that place; and are called “non-native” if they are
moved to another place where they do not naturally occur. Most non-native
species (sometimes also called exotic, nonindigenous, or alien species)
do not thrive in the new location because their new “home”
does not meet their needs. However, many do survive and can become
invasive.
Invasive non-native species can harm individual native species or
even entire ecosystems, and thus also impact those who depend on natural
systems for important resources and products. Unlike other kinds of
pollution, these “biological pollutants” can actually
increase in abundance over time and force out native species –
by competing with them (for space, water, or food), by eating the
native species, spreading new diseases, or so altering the habitat
that the native species can no longer survive. In fact, the impacts
of non-native species are now recognized as second only to habitat
alteration as a factor in the decline and extinction of our American
flora and fauna.
Water-dependent species and activities are especially threatened
because invasive non-native species spread rapidly in water -- e.g.,
in lakes, rivers and bays. Once the invaders have arrived, it can
be extremely difficult to control them without also hurting the native
species. The sooner you find them, the better chance there is to control
their spread. That is why preventing invasions and keeping a sharp
eye out for new invaders is so important – prevention and rapid
response are the keys to protecting natural ecosystems and the economic
activities that depend upon them.
A weed does not care if it’s growing on private or government
property; an invading fish or crab does not care if it is swimming
in state or federal waters. Because these aquatic invaders do not
recognize political or ownership boundaries, but threaten us all,
effective partnerships and coordinated efforts are essential -- everyone
has a stake, everyone has a role!
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