Hawaii’s Forests Are Changing: “You Won’t Find a Single Native Plant Species” in O’ahu’s Novel Ecosystems

Hawaii’s forests, once teeming with unique native life, now host unfamiliar "freakosystems"—entirely reshaped ecosystems driven by human impact, where native species are nearly nonexistent.

Oʻahu’s once-native forests are now filled with species from every continent, forming a human-made ecosystem unlike any seen before.

From afar, the forests of Oʻahu look like untouched tropical havens. But venture closer, and you’ll find that these ecosystems are no longer native to Hawaiʻi. Instead, they’ve become “freakosystems”—wild, self-sustaining environments built from species that never evolved together, shaped by human activity and climate change.

How Oʻahu’s Forests Became Strangers to Their Own Soil

Walk into the forests of Oʻahu and you’ll be greeted by a rich chorus of birdsong and the aroma of tropical greenery—but nearly all of it is foreign. These forests, once filled with endemic species found nowhere else, are now dominated by plants and birds from around the globe.

Centuries of human activity—deforestation, farming, and the introduction of invasive species—have pushed native life to the brink. Today, Brazilian pepper trees feed Chinese birds, and South American guavas grow wild in the Pacific. Oʻahu’s forests have become “novel ecosystems,” shaped entirely by human actions.

Survival in the Remix: When Invasive Species Keep Native Life Alive

Despite their chaotic origins, these new ecosystems aren’t entirely dysfunctional. Ecologists like Corey Tarwater and Jef Vizentin-Bugoni have discovered that non-native birds are now performing crucial roles, such as dispersing seeds for Hawaii’s last remaining native plants. Research shows some of these introduced birds are vital for plant survival.

" You wouldn't know unless you study them, but if you walk around any forest around Honolulu, there's not going to be one single native plant species there," said Tarwater.

A 2019 study led by Vizentin-Bugoni and Tarwater found that species introduced just a century ago are now filling the roles of extinct native birds—dispersing seeds, occupying ecological niches, and even forming mixed-species flocks. Vizentin-Bugoni was surprised to find that the way non-native birds and plants interact in Oʻahu’s forests is just as structured and organized as relationships in untouched ecosystems like the Amazon—despite their accidental origins.

These findings challenge the traditional view that non-native species are only harmful—in some cases, they may be keeping native life alive.

The Future of Conservation: Learning to Work With ‘Freakosystems’

The idea of returning Oʻahu’s ecosystems to their original state is increasingly seen as unrealistic. Many native species are extinct, and the landscape has changed beyond recognition. Conservationists now face difficult decisions about how—and whether—to manage these new systems.

Rather than remove all non-native species, some ecologists are embracing hybrid solutions. For example, they lure fruit-eating birds to native restoration sites using recorded calls to encourage seed dispersal. While these “freakosystems” may never resemble Hawaii’s ancient forests, they offer valuable lessons for the rest of the world as climate change and habitat loss reshape ecosystems everywhere.

News reference:
Jeferson Vizentin-Bugoni et al. ,Structure, spatial dynamics, and stability of novel seed dispersal mutualistic networks in Hawaiʻi.Science364,78-82(2019).DOI:10.1126/science.aau8751

Ponsford, M. “This Hawaiian island's 'freakosystems' are a warning from the future”https://www.bbc.com/future/article/20250403-the-new-hawaiian-freakosystem-emerging-on-oahu-accidentally-created-by-humans