Senior Seminar 2002
Introduced Species in Hawaii

History     Definitions     Impacts     Prevention     Management     Links     Literature Cited   

  Acknowledgements

Photo courtesy of: http://www.hcc.hawaii.edu/hawaii/pictures/img178.gif

History of Hawaii
Background
     The islands of the Hawaiian archipelago are thought to be 70 million years old (Loope 2002).  The evolution of organisms in Hawaii took place in extreme isolation, since the nearest continent is 4,000 km away (Jokiel 1998).  This isolation made natural invasions very rare.  Loope (2002) estimated that before the arrival of man, there was an average of one successful immigrant every 35,000 years.  The first Polynesians were thought to have arrived on the Hawaiian islands in 400 A.D, bringing with them many new species (Kirch 1982).  However it was not until the arrival of Captain James Cook in 1778, that the environment began to change dramatically.  With these first European settlers came a number of new species including; pigs, goats, sheep, and many ornamental and horticultural plants.  These early settlers inhabited the lower elevations of the islands, causing destruction through clear cutting and farming.  Techniques such as slash-and-burn farming were used to destroy large amounts of forests (Kirch 1982).  This destruction made it easier for introduced species to become naturalized.  The transformation of the lowland due to agriculture, the introduction of species and human predation are thought to have caused the extinction of half of the avifauna and many additional endemic species (Atkinson, 1977, Kirch 1982).  In the 230 years since Captain Cook's arrival, waves of humans from around the world have arrived on the islands, bringing with them a range of other species, and practices that continue to affect the islands to this day.  It is now estimated that an average of 20-50 new species arrive annually (Loope and Canfield 2000).

The Hawaiian Islands have a broad range of diverse ecosystems, including littoral, strand plant community, lowland dry scrub, desert, grassland, deciduous dry forest, cool dry forest (above 1,500 m), alpine scrub (above 2,000 m) and stone desert (above 3,000 m) (Reimer 1994).  The altitude of the islands range from sea level to 4,205 meters and the mean temperature ranges from 27° C at sea level, to 0° C at the highest altitudes (Reimer, 1994).

       
Image courtesy of: http://www.seaqmaui.com/Guests/taylor.htm                                       Image courtesy of: http://www.mycena.sfsu.edu/hawaiian/Agaricales.html

What makes Hawaii especially vulnerable?
The Hawaiian Archipelago is a chain of islands in the middle of the Pacific Ocean located in the northern hemisphere between approximately 19 and 22° latitude (Loope et. al 1998).  For 70 million years since their birth, the Hawaii has been the most isolated major island group in the world.  The nearest continent, North America, is separated by 4000 km of open ocean (Jokiel 1998).  This isolated location has contributed to Hawaii's vulnerability to human-related biological invasions.  The Hawaiian Islands have been far removed from the selective forces that have shaped evolution on its continental neighbors.  Hence, the organisms inhabiting the islands have evolved independently.  Additionally, the lack of predators on Hawaii can lead to population explosions of introduced species which in turn may cause the extinction of endemics.

Hawaii as a model
Hawaii is useful as a model in analyzing the role of introduced species.  This archipelgo has been a focus of ecological study for many decades, resulting in extensive documentation of the characteristics, impacts, and management of invasive species.  Also, the isolation of the Hawaiian Archipelago has lead to the magnification of impacts due to invasive species.  Lastly, the Hawaiian Islands can often be used in comparative studies since the majority of invasive species can be found there, including some of the most destructive invasive species (Loope and Canfield 2000). 

Hawaii is home to a variety of endemic species that may be highly vulnerable to competition with and predation by invasive species.  Remote islands are more likely to have endemic species because of their isolation and low immigration rates compared to islands near the mainland (Moulton and Pimm 1983). 

Definitions of terms
There are many terms used to describe invasive species that are recognized in the literature.  Often they are used interchangeably which can lead to confusion.  Therefore, it is necessary to clearly define the terms that will be used here.  

• Alien species- refers to a species that is transported or established outside of its native range (Hawaii Department of Forest and Wildlife).  This transport may or may not be intentional.  
  
• Introduced species- is an alien species that was transported intentionally.  Many authors use alien and introduced interchangeably. Within this web site we have followed the convention of the authors cited.  
  
• Invasive species- is an alien species that disrupts the normal functioning and/or structure of an ecosystem.
  
• A naturalized species is one that has become established and is self-sustaining in a new area.  
  
• A supertramp species is one that has high dispersability, can invade many distant habitats and has a negative effect on native flora and fauna (Townsend et al.).  

Impacts
Though not all introduced species will become invasive, those that do can greatly disrupt the normal functioning of natural systems.  Over the years approximately 50,000 species have been introduced to the United States from around the world for a variety of purposes (Pimentel et al. 2000).  One estimate indicated that invasive species may cost the United States $137 billion dollars per year (Pimentel et al. 2000).

There are many factors that must be considered when determining the cost of an invasive species.  Cost is often measured in the monetary direct and indirect damage done to property.  An example of indirect damage is cleaning up pigeon feces off of statues and buildings which when added to the cost of grain the pigeons consume can annually cost $1.1 billion (Pimentel et al. 2000).  Disease, rodents, weeds, insects, and birds can often cause direct damage.  For example, these invasive organisms can negatively impact crops and livestock, which results in a 4.5 % increase in crop prices for every 1% decrease in crop yield (Pimentel et al. 2000).  Disease can also cause huge impacts in the agricultural industry. This is especially important in Hawaii whose main source of income includes agriculture and tourism.
                
Alien species can often lead to a loss of biodiversity within an area through out-competing native species, predation, and alteration of the physical environment (Walker 1985; Cronk and Fuller 2001).  However, it is difficult to place a monetary value on biodiversity.  Lower biodiversity puts remaining species at a greater risk of extinction.   It has been estimated that 80% of endangered species may be threatened due to the presence of invasive species (Armstrong 1995, as cited in Pimentel et al. 2000).  With a decline in diverse and unique natural habitats, tourists are less likely to visit an area, which can lead to a decrease in revenue.  Another impact of invasive species is that they can often facilitate the further transfer of other alien species.  For example, feral pigs can often increase the dispersion of alien plants.  Invasive species have a worldwide impact.  However, Hawaii is more susceptible to their effects due to its location and natural history.

Prevention
Federal and local agencies are now banding together to help prevent the spread of alien species.  In 1999, President Clinton created an interagency Invasive Species Council, whose job it is to find ways to combat invasions by alien species (Pimentel et al. 2000).

Preventing alien species from entering the Hawaiian Islands is the most effective way of dealing with the decline of biodiversity due to these pests. In a recent paper by Kolar and Lodge (2002), a decision tree model was created for assessing alien species.  The three main categories in this tree are establishment, spread, and impact.  Using these guidelines, along with field data and computer modeling, species can be profiled and their effect may be predicted.  This method has been proven successful in determining a number of invasive fishes to the Great Lakes region, and it is thought that this model will prove to be useful to a variety of taxa.  Using this method to identify high risk species and then working at the establishment level with preventative measures is the most cost effective and certain way to combat this problem (Cote and Reynolds 2002).

Additionally, restoration and upkeep of natural habitats will help to prevent alien species from becoming established.  Native species have a better chance of outcompeting the aliens species in habitats in which they are adapted (Novacek and Cleland 2001). Lastly, education and public participation in stopping these alien species from entering Hawaii and other high-risk areas is essential.

There are numerous laws, acts and regulations (descriptions) that have been established to stop species coming in through all means of transport to the Hawaiian Islands.  Inspection, search dogs, and quarantines are all being used to aid in the prevention of alien species transport, but the public must become aware and knowledgeable to the impacts of these introductions for prevention to be successful.

Post-invasion Management
In general, there is not a comprehensive national system in place for detecting and responding to invasions by alien species.  It is often difficult to eradicate highly established invasives; post introduction management succeeds in controlling, rather then eradicating populations (National Invasive Species Council). There are different methods used in the control and management strategies of invasive species.  Two of the most commonly used methods are mechanical removal and chemical control, including physiological control.  Mechanical control is the physical removal of individuals.  In Hawaii, this method has been used to control the spread of Miconia calvescens and many other plants (Cronk and Fuller 2001).

Chemical control uses toxins to reduce population densities.  For example, a variety of chemicals have been used to control Fire Ants, which are a problem in the Continental U.S. and a potential invader to Hawaii.  These chemicals include delayed action toxins and quick acting insecticides, such as sprays and bait. Physiological control includes insect growth regulators as well as reproduction inhibitors (Banks 1990).  Chemical control can lead to environmental contamination and negatively impact endemics (Forschler and Evans 1994).

Additional control methods include genetic control, habitat modification, and biological control.  Genetic control is the introduction of genetically engineered individuals into an already established population of introduced species.  The genetically engineered individuals have altered environmental tolerances, reproduction, and other important processes.  Habitat modification is when the habitat is modified causing it to be less hospitable to the invasive population.  Biological control is the introduction of non-native species with the expectation that they will reduce the population of the targeted invasive.  This control method has the potential to backfire when the introduced control becomes an invasive itself (Carlton 2001).  It is important to restore native habitats and species after aliens have been controlled or eradicated, because a disturbed environment is more susceptible to reintroduction (Novacek and Cleland 2001).

Chemical controls, biocontrols and manual removal are all mechanisms that are used to deal with invasive species problems.  These strategies can be very labor intensive and costly.  On insects alone, the U.S. spends $1.2 billion each year on pesticides for agricultural purposes, $500 million of which targets invasive insects (Pimentel et al. 2000).  These controls methods can have indirect negative effects on the health of humans and endemic species.  Gonadal, phallic, and ovarian development is often negatively impacted by direct or indirect contact with many commonly applied pesticides (Moore, pers. comm.).  

Links
Filling in the Gaps in the Fight Against Invasive Species
This document was prepared by the Legislative Reference Bureau in 2001 and includes recommendations for a comprehensive alien invasive species control program for Hawaii.
http://www.state.hi.us/lrb/rpts02/gaps.pdf

Frequently Asked Questions of the Hawaii Natural Heritage Program
This site answers questions about several conservation-related topics in Hawaii.
http://www.natureserve.org/nhp/us/hi/faq.htm

Biotic Invasions: Causes, Epidemiology, Global Consequences and Control
This site provides a detailed summary of invasive species worldwide.
http://www.esa.org/ejissues/issues5.htm

Non-native Plants and Animals in the Hawaiian Islands
This site describes the history of introductions in Hawaii and discusses the current situation. The bibliography is also a useful resource.
http://www.geocities.com/i_love_plants/hawaii_essay.html

Hawaii Invasive Species Resources
This site provides an excellent list of links to other invasive species resources for Hawaii.
http://cain.nbii.gov/invasiveshi.shtml

The Hawaiian Ecosystems at Risk Project (HEAR)
Webpage that details what the USGS is doing in Hawaii. This is the center of information pertaining to Hawaii’s fight against invasive species.  It includes links to a variety of organizations including Hawaii State Island Species Committees, The Maui Invasive Species Committee, Big Island Invasive Species Committee, Oahu Invasive Species Committee, and the USDA's APHISi project.
www.hear.org/

Silent Invasion
This web page is from the Hawaii Conservation Organization and includes a link to a list of the top ten most unwanted organisms in Hawaii.
http://www.conservationhawaii.org/silent/

Literature Cited
Atkinson, I.A.E.  1977.  A reassessment of factors, particularly Rattus rattus L., that influenced the decline of endemic forest birds in the hawaiian islands. Pacific Science 31: 109-133.

Banks, W.A.  1990.  Chemical control of the imported fire ants.  In, Vander Meer, R. K.; K. Jaffe and A Cedeno. Applied myrmecology a world perspective. Westview Press, Boulder CO.

Carlton, J.T. 2001. Introduced species in the U.S. coastal waters: environmental impacts and management priorities. Pew Oceans Commission, Arlington, Virginia.

Cote, I. M. and J. D. Reynolds.  2002.  Predictive ecology to the rescue.  Science 298: 1181-1182.

Cronk, Q. C. B. and J. L.Fuller. 2001. Plant invaders: the threat to natural ecosystems. Sterline, VA: Earthscan.

Forschler, B. T. and Evans, G. M.  1994.  Argentine Ant (Hymenoptera: Formicidae) foraging activity response to selected containerized baits.  Journal of Entomological Science, 29: 209-214.

Hawaii Department of Forest and Wildlife.  Hawaii's Most Invasive Horticultural Plants: An Introduction. http://www.state.hi.us/dlnr/dofaw/hortweeds/ (19 September 2002).

Jokiel, P. L. 1998. Jokiel's illustrated scientific guide to Kaneohe Bay, Oahu. Hawaii Institute of Marine Biology. URL: http://cramp.wcc.hawaii.edu/ (2 December 2002).

Kirch, P.V.  1982.  The impact of the prehistoric Polynesians on the hawaiian ecosystem.  Pacific Science 36: 1-14.

Kolar, C. S. and D. M. Lodge.  2002.  Ecological predictions and risk assessment of alien fishes in North America.  Science 298: 1233-1236.

Loope, L. and J. Canfield.  2000.  Hawaii: A model for addressing invasive species.  United States Geological Survey: people, land & water. http://www.usgs.gov/invasive_species/plw/hawaii01.html (27 November 2002)

Loope, L.L.  Hawaii and the Pacific islands.  URL http://biology.usgs.gov/s+t/SNT/noframe/pi179.htm (27 November 2002)

Moulton, M. P. and S. L. Pimm.  1983.  The introduced Hawaiian avifauma: biogeographic evidence for competition.  American Naturalist 121: 669-690.

National Invasive Species Council.  National Management Plan.  URL http://www.invasivespecies.gov/council/execsumm.shtml , (16 November 2002).

Novacek, M. J. and E. E. Cleland.  2001.  The current biodiversity extinction event: scenarios for mitigation and recovery.  Proceedings of the National Academy of Science 98:5466-5470.

Pimentel, D., L. Lach, R. Zuniga, and D. Morrison.  2000.  Environmental and economic costs of nonindigenous species in the United States.  Bioscience 50: 53-65.

Reimer, N.J.  1994.  Distribution and impact of alien ants in vulnerable Hawaiian ecosystems.  Pp 11-22.  In: D.F. Williams, editor.  Exotic Ants, Biology, Impact, and Control of Introduced Species.  Westview Press, Boulder CO.

Townsend, C. R., M. Begon, and J. L. Harper.  Essentials of ecology: second edition.  http://www.blackwellpublishing.com/Townsend/Glossary/GlossaryS.asp (2 December 2002).

Walker, R. L.  1985.  Status, research and management needs for alien biota: a summary and commentary.  Pp 372-373 in C. P. Stone and J. M. Scott, editors. Hawaii's terrestrial ecosystems: preservation and management. University of Hawaii Press for Cooperative National Park Resources Study Unit, Honolulu, Hawaii, USA.

Acknowledgements
We would like to thank the following people for their guidance and support in helping us bring this project together.

• Mary Bogue - Wildman Science Library Manager
  
• Bill Buskirk - Professor of Biology at Earlham College
  
• John Iverson - Professor of Biology at Earlham College
  
• Sara Penhale - Science Librarian at Earlham College
  
• Brent Smith - Professor of Biology at Earlham College
• Elly Vandegrift - Visiting Instructor of Biology at Earlham College
  

Designed by: S. Danyi, C. Hand, J. Jamison, H. Meckel, S. Murphy, S. Pasachnik, S. Schiro, and R. Welsh                                      
Contact: pasacst@earlham.edu
Last Revised: 8 December 2002