State’s native ecosystems are under attack by some very unsuspecting subjects
Oahu Army Natural Resources Program, Directorate of Public Works, U.S. Army Garrison-Hawaii
HONOLULU — Carnivorous wolf snails, Jackson’s chameleons, pigs, goats, deer, fountain grass, strawberry guava, rats, slugs, devil weed, ants, coqui frogs, sheep.
This listing is an abbreviated one of some of the most destructive human introductions to Hawaii’s native ecosystems to date.
Some were intentional introductions, while others were accidental hitchhikers on incoming cargo.
Regardless of why they were brought here, these introduced plants and animals (and hundreds more) have proven to be highly invasive species in Hawaii’s natural ecosystems.
Invasive species, also known as “pests” or “exotics,” are plants and/or animals that have been introduced into a new environment and have aggressively adapted to conditions in the wild.
And while not every non-native species becomes an invasive pest, many do.
Once established here, these introduced species enjoy a true Hawaiian vacation. They rapidly increase in numbers because they are free from the constraints of their homeland, such as extreme weather, disease and natural predators.
The Hawaii State Department of Agriculture regulates the importation of new species, which are evaluated based on the risk they pose and their history of invasiveness worldwide.
Importation of reptiles is prohibited because Hawaii has no native reptiles. The destruction caused by invasive reptiles in other places, such as Guam (brown tree snake) and Florida (python), is well known.
The Hawaii Weed Risk Assessment is a tool used to evaluate the invasive potential of plant species. Plants scoring high on the HWRA are likely to become destructive influences on the native landscape.
Natural resource managers and technicians are in the field every day, battling invasive species that are already established. Additional support from the community, focused on preventing the spread of new or existing invasive species, would go a long way toward winning the fight to protect Oahu’s native plants and animals.
(Editor’s note: Welch is an environmental outreach specialist with OANRP.)
Hawaii’s Most Wanted Invasive Species
Listed herein is a rundown of some of the most destructive invasive plant and animal species found in Hawaii, along with what you, the public, can do to help.
If you sight an invasive species, contact the Oahu Army Natural Resources Program at 656-7741.
Name: Rosy Wolf Snail (Euglandina rosea)
Native to: Florida
How’d it get here: Intentionally introduced in the 1950s to control the giant African snail, another introduced mollusk. With little to no predators here to keep it in check, the rosy wolf snail has roamed far and beyond its original sites and can now be found in some of Oahu’s most remote native forests.
Crimes committed: Eats Hawaii’s native snails, including the endangered kahuli tree snail, which only exists in very small numbers on Oahu.
What OANRP is doing: Staff build predator barriers loaded with deterrents in areas where rosy wolf snails threaten endangered Hawaiian kahuli tree snails.
What you can do: N/A
Name: Jackson’s Chameleon (Chamaeleo jacksonii, subspecies xantholophus)
Native to: Kenya and Tanzania
How’d it get here: Brought in through the pet trade in the ‘70s under a legal pet store import permit, the Jackson’s chameleons escaped from the store owner’s property and today thrive in the wild island-wide.
Crimes committed: Eats native Hawaiian insects and mollusks, including the endangered kahuli tree snail.
What OANRP is doing: The Army funds research on Jackson’s chameleons’ eating habits on Oahu and builds predator barriers to keep them out of endangered kahuli habitat.
What you can do: It is illegal to release Jackson’s chameleons into the wild. If you have a pet Jackson’s chameleon and no longer wish to keep it, contact the Hawaii Department of Agriculture at 643-PEST (7378), or the University of Hawaiian Tree Snail Conservation Lab at 956-6176.
Name: Devil Weed (Chromolaena odorata)
Native to: Central America
How’d it get here: Abundant in Guam, the plant likely hitched a ride to Kahuku Training Area via military vehicles or personal gear.
Crimes committed: Toxic to humans, animals and even other plants, devil weed can grow up to 12 feet tall and produce 800,000 seeds in a year.
What OANRP is doing: The Army has spent a large amount of time and money controlling the infestation at KTA since the plant was first discovered in 2011. More than $125,000 will be spent this year to continue control efforts. Also, staff constantly conduct weed surveys along roads and trails, and in the forest, to detect weeds in new locations on Army lands.
What you can do: Prevent devil weed from spreading. Motocross bikes should be hosed thoroughly before entering and exiting Kahuku motocross track, and Soldiers should wash all vehicles and personal gear prior to exiting KTA. Reserve a wash rack with Range Control when making reservations to train on the range.
Name: Fountain Grass (Cenchrus setaceus)
Native to: Africa
How’d it get here: Intentionally introduced as an ornamental landscape plant, fountain grass recently spread to steep cliffs on Ohikilolo Ridge above Makua, likely by trespassing hikers.
Crimes committed: Fuels brush fires, causing fires to become more frequent and destructive. Fountain grass is easily spread by wind, animals and people and is extremely invasive. It’s out-competing native Hawaiian plants for areas to grow.
What OANRP is doing: The Army has treated the incipient fountain grass population in Makua via aerial helicopter sprays. Staff constantly conducts weed surveys along roads, trails and the forest to detect weeds in new locations on Army land.
What you can do: Prevent fountain grass from spreading. Be sure to thoroughly wash boots and gear after hiking at spots such as Diamond Head Crater and Lanikai Bunkers, where the grass is located, in order to prevent hitchhiking seeds from entering new areas.
Name: Feral Pig (Sus scrofa)
Native to: Europe
How’d it get here: The smaller, docile Polynesian variety (typical pot-bellied pig) was brought to Hawaii on the first voyaging canoes as early as 400 A.D. Larger, more aggressive European varieties were brought in 1778 with the arrival of Captain James Cook.
Crimes committed: Without predators or herbivore competitors, pigs adapted well to the Hawaiian wet forest and rapidly established large feral populations (a single pair and their offspring can, theoretically, produce 15,000 pigs in five years).
Pigs knock down and feed on native understory plants and roto-till the forest floor to get earthworms and other grubs; however, disturbed earth collects rainwater, providing the perfect breeding grounds for mosquitoes that can transmit avian malaria to native forest birds.
What OANRP is doing: Staff build fences to keep pigs out of forest ecosystems, and fenced areas are kept pig-free through hunting and regular monitoring trips.
What you can do: N/A
Name: Rats (Rattus species)
Native to: India, Mongolia and Indo-Malaysian region
How’d it get here: Three species of rats arrived in Hawaii as stowaways over time: The Polynesian rat arrived in the 5th century on the first canoes to reach the Islands, while the Norway rat and black rat arrived on European ships in the 1800s.
Crimes committed: Feeds on native birds and their eggs, native plants (including fruits and seeds), native tree snails and native insects.
What OANRP is doing: Rat-proof barriers are constructed around endangered populations of Hawaiian tree snails, and large-scale trapping grids are placed around populations of endangered plants and the elepaio, an endangered native Hawaiian forest bird.
What you can do: N/A
Hawaii’s conservation professionals have long recognized the threat invasive species pose for Hawaii’s natural resources and the negative impact these changes will have for human use of these resources. For this reason, the Hawaii Invasive Species Committee has proposed that Hawaii Gov. Neil Abercrombie proclaim March 4-8 as Hawaii Invasive Species Awareness Week.
The aim is to enlist the public’s help in fighting the battle to preserve Hawaii’s remaining native ecosystems.
For further information on destructive plants and animals introduced to the Hawaiian Islands, visit the following organizations and their websites:
•U.S. Army Garrison-Hawaii Environmental Compliance Guide, www.garrison.hawaii.army.mil/sustainability/AtoZ/PetOwnership.pdf.
•U.S. Army-Hawaii Sustainability and Environmental Management, www.garrison.hawaii.army.mil/sustainability/NaturalResources.aspx.
•Hawaii Invasive Species Partnerships, www.hawaiiinvasivespecies.org.
•State of Hawaii Department of Agriculture, hdoa.hawaii.gov.