A global study has found that invasive animal species are threatening island ecosystems more than native animal extinctions. 

What's happening?

The University of Hawaiʻi at Mānoa School of Life Sciences research, published in the journal Proceedings of the National Academy of Sciences, revealed a disturbing discovery that could reshape conservation priorities around the world. 

Experts analyzed data from 120 islands across 22 archipelagos to understand how native, extinct, and introduced frugivores — fruit-eating animals — can affect plant seed dispersal. 

They found that introduced mammals, such as pigs and rats, often replaced native birds, bats, and tortoises that once carried seeds to new areas. 

However, unlike their native counterparts, these newcomers often destroy seeds instead of dispersing them, which disrupts how island forests regenerate.

The study also found that species introductions now outnumber extinctions, with introduced species making up 44% of the island fauna, compared to 23% extinct species. This effect impacted 92% of the islands examined.

Why are these introduced species concerning?

"Understanding how introduced species reshape ecological interactions is crucial for planning effective conservation strategies," said study co-author Donald Drake, who added that these creatures can "fundamentally alter ecological interactions on a global scale."

In addition to being one of the study's co-authors, Drake is a professor in the University of Hawai'i at Mānoa School of Life Sciences and interim director of Lyon Arboretum. 

He shared that the study's findings "underscore the need for proactive management to preserve [Hawai'i's] unique biodiversity," especially since its native plants depend heavily on birds for seed dispersal.

When native animals disappear and invasive or introduced species take their place, the entire seed-dispersal system is affected, which could threaten the future of island forests. 

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Plants that once relied on native birds or bats to spread their seeds may no longer reproduce effectively, which can lead to a decline in forest health, biodiversity, and watershed stability.

Because invasive species often outcompete native wildlife for food, space, and other vital resources, their spread can ripple through ecosystems — reducing pollination and even allowing certain pests or diseases to thrive.

In Hawai'i, the loss of native frugivores has slowed the regeneration of forests containing plants such as lama, hōʻawa, and olopua — species that are central to ecosystem balance, watershed health, and local cultural practices that rely on native plants.

What's being done about the change in Hawaiʻi's ecosystem?

Conservation work in Hawaiʻi now focuses on managing invasive animals, protecting remaining native frugivores, and restoring disrupted seed-dispersal networks. These efforts can help to maintain biodiversity and stabilize natural resources. 

Similar strategies are appearing elsewhere: projects in Florida have targeted invasive pythons to protect native wildlife, while communities in California are reintroducing native plants to restore habitats and conserve water. 

For individuals seeking to help the issue, choosing native plants, supporting local restoration efforts, and being mindful about introducing new species can all make a difference.

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