Hawaii, like many other islands that are far away from other land areas, faces challenges caused by non-native plants and animals that harm the variety of living things naturally found on the islands.

Historical examples

Hawaii is the most isolated large land area in the world. This isolation has caused many species to be found only in Hawaii. These unique species are often harmed by competition from non-native animals and plants. Hawaii has lost many species over time (List of extinct animals of the Hawaiian Islands). While not the only reason, introducing non-native species has caused many native species to decrease in number or become extinct.

Non-native species can reach Hawaii through several ways. Some arrived by accident, such as rats, fire ants, coqui frogs, mosquitoes, and coconut rhinoceros beetles. Others were brought to grow in farms or gardens but later spread into wild areas, like miconia, pigs, and goats. Some were brought intentionally for activities like hunting, such as axis deer, or for controlling pests, like mongoose or cane toads.

The mongoose was brought to Hawaii in the late 1800s to help reduce the number of rats in sugar cane fields. However, the mongoose population grew large, and they did not control the rat population as intended. Instead, they harmed native ground-nesting birds, snails, and palms.

Another example is the fire tree, a small shrub introduced in the 1800s from the Azores, Madeira, and Canary Islands as an ornamental plant or for firewood. Now, it harms native plants in young volcanic areas, lowland forests, and shrublands by forming thick groups of the same plant. Another example is the strawberry guava, introduced in the early 1800s as a fruit to eat. Today, it harms Hawaii’s rare native plants and animals by growing in thick groups that block sunlight and cover the ground with dense roots.

Potential harm from invasive species

Invasive species harm the variety of living things by causing illness, acting as predators or parasites, competing for resources, changing habitats, or mixing genes with local species.

Invasive species often bring new diseases that native species have not faced before. For example, some biting flies in Hawaii carry diseases, while others cause health problems. Mosquitoes introduced to Hawaii have spread avian malaria and increased the risk of dengue and West Nile virus (which are not yet in Hawaii).

Other native species also suffer from diseases caused by invasive species. The once-dominant koa tree has been killed by koa wilt, a disease likely brought to Hawaii through an ornamental acacia plant. The 'ohi'a tree is now affected by Rapid Ohia Death.

Invasive predators can greatly reduce the numbers of native species or even cause them to disappear, as native animals may not have ways to protect themselves from these new threats.

Introduced species often survive better than native species and compete for food or other resources. For example, the strawberry guava tree is a major invasive species in Hawaii. It harms native plants, breaks up natural areas, changes ecosystems, and provides shelter for harmful fruit flies that damage crops.

Invasive species can change environments in many ways depending on how they eat and interact with their surroundings. These changes, along with competition, can reduce the amount and type of resources available to native species.

Hybridization happens when two different species mate and have children that carry genes from both parents. If an invasive species is much more common than a native species, their genes may mix so much that the native species loses its unique traits and may go extinct. For example, hybridization between introduced mallards and the native Hawaiian duck (koloa maoli) and between the rare European white-headed duck and the invasive ruddy duck may lead to the extinction of the native species.

In Hawaii, the culture is closely connected to the environment and native species. Practices like chants, ceremonies, hula, and traditional access to sacred places depend on native plants and animals. For example, taro (kalo in Hawaiian) is considered sacred in Hawaiian creation stories. The introduction of the golden apple snail, which eats taro, threatens the survival of this culturally important plant.

Threats to Hawaii's ecosystems

Hawaii is facing a serious problem with invasive species that harm the islands' endangered plants and animals, the environment, and the health of people. Invasive species exist worldwide, but Hawaii is especially vulnerable because it is an island. All of Hawaii's islands have been heavily affected by invasive insects, plants, hoofed animals like deer, goats, pigs, and other pests. Feral pigs eat the eggs of endangered birds and damage native plants. Rosy wolfsnails from Florida eat native snails. Weeds like Australian tree fern and Miconia calvescens plants block sunlight and harm native plants. Coqui tree frogs make loud noises that bother tourists, eat native insects, and lower home values.

Invasive species also threaten Hawaii's coral reefs, which support a tourism business valued at about $10 million. Freshwater invasive species harm ecosystems as well. In 2003, Lake Wilson was invaded by the floating water fern Salvinia. This plant outcompeted native species and fish. Cleaning up the lake has cost the state over $1 million.

Freshwater fish have been introduced to Hawaii by sport fishermen and people who released pet fish into local water. Trout, bass, and other fish were brought to lakes and streams. Pet fish like guppies, suckermouth catfish, and swordtails were also released. Suckermouth catfish dig into the ground, harming wildlife. Even guppies can spread disease to native fish.

Insects also cause major problems for Hawaii's environment, crops, and people. Little fire ants, which are native to Central and South America, were brought to Hawaii on imported plants. These tiny ants can sting painfully and attack in swarms.

A major threat to Hawaii's coffee crops is the coffee berry borer. This pest can destroy entire coffee crops, but some farmers use pesticides to control it. Others report that the borer is becoming resistant to these chemicals. Scientists are working to find out how the pest arrived in Hawaii and how to eliminate it.

The coconut rhinoceros beetle was first found in Hawaii in 2013 on a golf course in Pearl Harbor. This large beetle damages the growing parts of coconut trees, making them more likely to get sick. Scientists and government agencies are trying to remove the beetle from Hawaii.

Another insect harming Hawaii is the small hive beetle, which destroys bee hives and honey production. This infestation harms both commercial honey production and wild bees, which are important for pollinating plants. If this trend continues, it could cause serious problems for Hawaii's ecosystems. Spiders like the brown widow, brown violin, Asian spinyback, and pale leaf spider have also been found in Hawaii. These spiders arrived on bananas from tropical regions.

On land, invasive species are a big problem because Hawaii lacks many natural predators for these animals. Invasive predators often become the top of the food chain, harming small animals, birds, insects, and plants.

Chameleons like the veiled chameleon and Jackson's chameleon were brought to Hawaii through the pet trade in the 1970s, despite laws against importing them. These chameleons eat insects, leaves, flowers, and even small mammals and birds. Their feeding habits, lack of predators, and ability to survive in different environments harm Hawaii's ecosystems.

The coqui frog also threatens Hawaii's environment. It makes loud noises, eats native insects, and could become a food source for the brown tree snake.

Hawaii is working hard to stop the spread of the brown tree snake, which caused major problems in Guam. This snake has destroyed bird, bat, and lizard populations and caused human issues like snake bites and power outages. If the snake reaches Hawaii, it could cost up to $123 million. Scientists fear it might arrive on ships from Guam.

Feral pigs, which were released or escaped from farms, have created a large wild population in Hawaii. These pigs destroy plants and habitats, and their burrowing harms bird nesting areas and causes erosion. In mountainous areas, they damage nests of seabirds like the Newell's shearwater and Hawaiian petrel. Their burrows also create pools of water filled with feces, which are ideal for mosquitoes. More mosquitoes mean more diseases for native birds.

Hawaii is taking steps to protect its environment from invasive species, but the problem remains serious.

Economic impact

Allowing invasive species to spread in Hawaii causes big problems for many important industries in the state. A 2002 study by the Legislative State Reference Bureau showed that nonnative snails, insects, and viruses have harmed the recovery of taro root crops, which is worth about 2 million dollars in the state. The taro aphid, which attacks dry land taro plants, causes 90% of crops to be lost, hurting local farmers. To stop invasive pests, all taro roots must be removed from an area for one year, which makes the economic harm worse. The papaya industry, the fifth largest commodity in Hawaii and worth 16 million dollars each year, has also been harmed by invasive species. The Papaya ringspot virus has killed trees and ruined fruit that can be sold. In addition, fruit flies introduced to Hawaii have caused countries like Japan and California to stop buying Hawaiian papayas, cutting off about 300 million dollars in potential sales.

Since 1985, four types of insect pests have attacked the sugar cane industry, costing farmers more than 9 million dollars. Rats and other rodents have also damaged sugar cane crops, causing between 6 and 10 million dollars in losses each year during the 1990s. Invasive rats and rodents also eat about 5-10% of the macadamia nut crop, causing 1.8 to 3.6 million dollars in direct damage to the industry. Mongooses were brought to Hawaii in the late 1800s to control rodent populations, but they did not help and instead caused harm by driving native birds and insects to extinction and attacking local poultry. This shows how difficult it is to control invasive species, as quick fixes can have harmful effects on ecosystems. Another example is the Indian myna, introduced to control sugar cane-eating worms, which led to the spread of an invasive weed called Lantana camara.

Because of the economic harm shown in these examples, fighting invasive species is a "recurring legislative concern." To remove current invasive species and learn about risks from new ones, the legislature would need about 50 million dollars in funding each year. Right now, funding to fight invasive species is only 10-15% of what is needed, with an additional 6% coming from federal sources. Because of the high costs, especially during economic challenges, the government should focus on long-term funding from reliable sources and work to prevent new invasions.

The Hawaii Invasive Species Council

In 2002, a report from the state legislature identified problems with funding for controlling invasive species and the dangers they pose. Because of this, the Hawaii Invasive Species Council (HISC) was created. The HISC is led by two state departments: the Department of Land and Natural Resources and the Department of Agriculture. It also includes members from the University of Hawaii, the Hawaii Department of Business and Economic Development and Tourism, the Hawaii Department of Health, and the Hawaii Department of Transportation. The HISC has five working groups, each led by a member agency, that focus on prevention, managing existing pests, public awareness, research and technology, and natural resources. The HISC helps guide and organize efforts among state departments, federal agencies, and local groups to control and remove invasive species. It also ensures a clear understanding of issues and supports programs across the state to stop invasive species before they spread. These programs test new methods to address invasive species, which can later be used by other agencies.

The HISC works with groups called Island Invasive Species Committees (ISCs). These committees use HISC funding along with money from federal, state, county, and private sources to tackle invasive species that harm their islands. ISCs include partnerships between government agencies (federal, state, and county), private businesses, and local landowners. Each committee (KISC, OISC, MISC, MoMISC, and BIISC) focuses on protecting their island from invasive pests using prevention, early detection, quick action, and control methods. These efforts are supported by paid staff and field crews. The goal of the ISCs is to protect agriculture, important water sources, human health, quality of life, Hawaiian traditions, and Hawaii’s unique plants and animals.

Right now, the HISC has less than $4 million in funding because state support was cut by 50% due to a tough economy. The current state budget includes $2 million for the program, but this amount might be reduced if the state runs out of money, which could make it harder to fight invasive species.