ALIEN SPECIES
Alien species are those moved by humans to areas outside
of their native ranges. Once transported in this manner, they become
removed from the predators, parasites, and diseases that kept them in
balance in their native environments. As a result of losing these
controls, they often become pests in the areas into which they are
introduced. In Hawai`i, alien species have created a tremendous
amount of damage to our environment and economy and pose an
ever-increasing threat to Hawai`i's magnificent natural resources,
native species, and ecosystems.
Alien species threaten our environment and livelihoods in many ways. They can reduce water quality and quantity by increasing runoff and erosion and this, in turn, degrades near-shore marine ecosystems like coral reefs. They present a continued threat to Hawai`i's agricultural industry and home gardening, with every passing year seeing the arrival of new agricultural plant pests into the state. They pose a potential threat to human health in Hawai`i because many of the world's most dangerous infectious diseases are currently absent from the State. Hawai`i's economy is directly tied to the quality of its environment, and alien species introductions have the potential to compromise the foundation upon which the State's economic wellbeing rests. Because of increased trade volume with other parts of the world, the threat that alien species pose to Hawai`i's environment, native species, economy, and quality of life will not diminish with time.
Alien species have already had a
tremendous effect on Hawai`i's unique flora and fauna. Because of its
isolation, Hawai`i originally had thousands of species found nowhere
else on Earth. But it has suffered the highest rates of extinction of
any area of the United States and one of the highest rates anywhere
in the world, with hundreds or possibly thousands of unique species
already extinct. The primary agent of this remarkable loss of native
biodiversity has been the massive introduction by humans of alien
species to the Hawaiian Islands. Many thousands of Hawai`i's unique
species still exist, but hundreds of these are currently listed as
endangered, and hundreds more await listing. Alien species constitute
the primary cause of endangerment for virtually all of these
endangered plants and animals. The threat of further losses due to
alien species introductions to Hawai`i remains large.
Alien species are especially disruptive on oceanic islands like Hawai`i because they introduce ecological challenges that native species have never faced before. Also, the sheer volume of introductions overwhelms native species. It has been estimated that before the arrival of humans, new species became established in Hawai`i (under their own power or blown by storms) once every 70,000 years. Now Hawai`i receives in excess of 20 new species per year. Consequently, native species succumb to the sheer magnitude of new ecologial challenges imposed upon them.
The greatest new ecological challenges presented by alien species
in Hawai`i are the following:
(Click on the links below to see more information.)
Other significant perturbations to Hawai`i's native communities include diseases, inter-specific competition, seed predators, plants that poison nearby plants, and carnivorous snails.
Alien species arrive in Hawai`i in
a variety of manners. Many, such as ornamental plants, are legally
imported and planted, but then spread to forests when they reproduce
and their seeds are blown there by the wind or carried by animals
such as birds. Others, like agricultural insect pests and a variety
of other flying insects arrive as unintentional hitch-hikers on
agricultural produce, cargo, or airplanes. Still other species, like
a variety of snakes and other reptiles, are smuggled illegally into
the state to satisfy their owners' urge to have an exotic pet. Each
of these pathways can be important for introducing to Hawai`i
unwanted alien species that can establish populations and become
serious pests.
State and federal agencies and non-profit conservation organizations have banded together to identify and correct a number of gaps in efforts to keep alien species out of Hawai`i. This group is called the Coordinating Group on Alien Pest Species (CGAPS) and has produced a glossy color brochure that highlights some of the worst alien species (like the brown tree snake) which threaten to arrive in Hawai`i, ecological and economic consequences of some alien pests already in the islands, reasons why alien species are a problem in the state, gaps in Hawai`i's prevention and control system, and actions that both government and the average citizen can take to help protect Hawai`i from additional alien pests. This brochure is available from DLNR for teachers and other educators for use in increasing public awareness of the alien species problem.
[Photos: top - Kahili ginger (Hedychium gardnerianum) was
introduced for its attractive flowers, but is one of the primary weed
threats to native rainforest; middle - Red-billed Leiothrix
(Leiothrix lutea) is an important disperser of alien plant
seeds in native forest (photo by Jack Jeffrey); bottom - Glory bush
(Tibouchina urvilleana) is another attractive ornamental that
threatens native rainforest on the islands of Kaua`i and
Hawai`i.]
What you can do to help protect Hawai`i from alien pests
Division of Forestry and
Wildlife
1151 Punchbowl Street, Rm. 325
Honolulu, Hawai`i 96813
Phone 808-587-0166, FAX 808-587-0160
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