A recent white paper, co-authored by Pacific RISA’s Laura Brewington and the U.S. Invasive Species Advisory Committee (ISAC) highlights the critical importance of islands to the United States, and the harmful impacts that invasive species have on them. In “Island Resilience is American Resilience: Actions Towards Reducing the Impacts of Invasive Species on US and US Affiliated Islands,” the authors outline how U.S. and U.S.-affiliated islands, such as Puerto Rico, Guam, Hawaiʻi, and the Freely Associate States, contribute vital components to national and global food production, economies, biodiversity, cultural heritage, and security.

However, invasive species pose a significant threat, second only to climate change, causing severe damage to these areas. Invasive species are responsible for nearly 90% of recorded species extinctions on islands and have caused billions of dollars in damages. The economic impact on U.S. and U.S.-affiliated islands is significantly higher than on the continental U.S., partly due to the high burden of invasive species on islands like Hawaiʻi. As an added threat, invasive species on these islands are merely one flight away from continental areas where they are not already established, posing immense risks to agriculture, industry, and biodiversity on the U.S. continent.

“U.S. and U.S.-affiliated islands are strategic strongholds for national security, global biodiversity, and economic stability—yet they remain uniquely vulnerable to invasive species. Federal leadership and investment in biosecurity will ensure these critical regions remain resilient and sustainable.” ~ Laura Brewington, the paper’s lead author

The high costs of invasion

Because many islands are geographically isolated, they are also highly susceptible to invasive species. Indigenous communities historically sustained themselves with minimal external influence, but modern trade and travel have increased the risk of invasive species introductions. The authors found that invasive species have cost U.S. and U.S.-affiliated islands over $16 billion in cumulative damages over the past 40 years. For instance, the State of Hawaiʻi has an almost equal number of nonnative plant species as the entire continental U.S., despite its small size. Invasive species reduce climate resilience by altering ecosystem structure and function, negatively impacting livelihoods, quality of life, food security, and culture. These impacts are so severe that at the 2024 Micronesian Islands Forum meeting, island leaders directly addressed them in a letter to then-President Joe Biden.

Recommendations for federal action

The authors outlined four priority action areas where the U.S. federal government could begin to address these challenges to islands: terrestrial biosecurity, marine biosecurity, control measures and long-term impact reduction, and social and capacity conditions. For example, improved prevention efforts and jurisdictional coordination are needed to address terrestrial invasive species. Federal and local agencies should collaborate to enhance prevention at ports of entry. U.S. and U.S.-affiliated islands contain significant marine resources, including coral reefs, which are threatened by invasive species. Improved marine biosecurity measures are essential to protect these ecosystems.

Meanwhile, many islands already suffer from a high burden of invasive species. In these locations, biologically based control technologies and chemical controls are crucial tools for managing invasive species and must be developed with local conditions and capacity in mind. Post-disturbance restoration efforts will also be needed to recover ecosystems affected by invasive species, such as wildfire prone areas in Guam or Hawaiʻi. In all islands, federal agencies need to offer more support local capacity for invasive species management: investments in education, outreach, and professional development are essential to build local expertise and trust.

Federal agencies must address the urgent need for coordinated efforts to manage invasive species on U.S. and U.S.-affiliated islands, and this white paper offers a blueprint for how to do so in ways that are appropriate to the needs and challenges facing islands today. These efforts will be vital for enhancing climate resilience, protecting biodiversity, and supporting the well-being of all U.S. island communities.

Featured image: Pampas grass, an invasive grass in all the main islands of Hawaiʻi and other parts of the Pacific Islands. Image credit: Maui Invasive Species Committee.