Invasive Species
Alaska Region   



Northern Pike eating salmon. ADF&G.

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!

Last updated: May 12, 2010

Invasive Species
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