Invasive Plants of Hawaii & the Pacific Islands

With increasing international travel, commerce, and the consolidation of military operations on Guam, invasive plants pose a significant threat to the U.S. affiliated Pacific Islands and Hawaii. Tropical forests provide critical habitat to endangered plants and animals and provide vital watershed protection. Island ecosystems and economies are particularly vulnerable to invasive species impacts. The USDA Forest Service, through State and Private Forestry, Forest Health Protection, funds a grant program in Hawaii and the affiliated Pacific Islands that is used for invasive plant inventory and control activities, as well as educational initiatives.

Assessment

• A significant part of the solution in the Pacific is, and will continue to be, capacity building and partnerships. Hawaii and most of the U.S. affiliates have formed local and regional collaborative groups to coordinate invasive species issues of common concern.
• The invasive species organizations and their inter-relationships within the state of Hawaii can serve as a model for other states; however, recent cuts in state budgets for these organizations are placing their effectiveness at risk.
• Disturbance agents, such as typhoons and fire, result in conditions conducive to invasive plant establishment. Climate change is expected to increase the severity of these disturbance agents.
• Difficulties in obtaining supplies and in handling logistics have hampered the implementation of control efforts on several islands.

Priority Species Highlights

• Merremia

  

  Wood rose (Merremia tuberosa) is a fast-growing, woody, climbing vine whose mature seed pods look like a wooden rose. Merremia’s rapid growth quickly enables it to occupy the canopy, smothering trees and smaller plants. Merremia is present on the four largest islands of Hawaii and multiple other Pacific islands.

  Photo: Merremia and its flower,
  by Forest & Kim Starr

  Additional Information

• Chain-of-love

  

  Chain-of-love (Antigonon leptopus) is one of the most aggressive weeds occurring in the islands of the Pacific. Chain-of-love engulfs native trees, out-competes understory plants, and alters fire regimes.

  Photo: Leaves and flowers of Chain-of-Love,
  by Forest & Kim Starr

  Learn More

• Leucaena

  

  Leucaena (Leucaena leucocephala) was introduced as animal fodder and fuel wood due to its ability to reproduce quickly and form dense stands. Leucaena is associated with disturbed, open habitats and resprout quickly after burning or cutting.

  Photo: Young Leucaena trees,
  by Forest & Kim Starr

  Additional Information

• Albizia

  

  Albizia (Falcataria moluccana were planted in across Hawaii in forestry planting efforts in the early 20th century. It can grow up to 15 feet per year and its large branches fracture and drop with no apparent disturbance.

  Photo: Albizia along roadside,
  by Hawaii Department of Land and Natural Resources

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Prevention

• The Pacific Invasives Learning Network draws upon international resources in the Pacific to provide technical assistance and capacity building for invasive species management. The Forest Service coordinates with this network and other programs and organizations in the Pacific Islands through the Pacific Invasives Partnership.
• Most of the Pacific Islands have developed strategic plans for dealing with invasive species. State and Private Forestry is assisting with the governments in Guam and American Samoa to complete these plans.
• Hawaii has developed a rigorous and comprehensive weed risk assessment process that is used to assess the risks from new invasive plants.
• Public education programs are ongoing on all the Pacific Islands.

Early Detection and Rapid Response

• In Hawaii, periodic resurveys of roadsides, botanical gardens, nurseries, recreation areas, and private lands have resulted in the early detection of numerous invasive plants.
• Hawaii has a very comprehensive program of early detection followed by treatments. This is the primary role of the Invasive Species Committees on each island.
• In the US-affiliated Pacific Islands, ownership issues can often delay or slow initial attempts at rapid response or control.
• In Palau, there is an emphasis on surveying along the recently completed Compact Road, which has resulted in the treatment of new invasive plant occurrences.

Control and Management

• Capacity building for control efforts is developed through training conducted by international NGO’s, other governments (New Zealand, Hawaii), and the Forest Service.
• Efforts to find viable biocontrol agents are ongoing, involving several countries, NGO’s, and universities.
• In Hawaii, current efforts to introduce an insect biocontrol for strawberry guava have met with resistance from people who see the program as a threat to the environment.

Rehabilitation and Restoration

• The Forest Service is working with partners within the state of Hawaii to insure that key native species are available for restoration.