Hawaii introduced red mangroves in 1902; 124 years later, they clog waterways
Red mangroves, introduced to Hawaii in 1902 for erosion control, have become an invasive species that clogs waterways and threatens native ecosystems. The situation serves as a cautionary tale regarding the long-term ecological consequences of introducing non-native species.
Why it matters
It illustrates the unintended environmental impacts of historical land management decisions and the ongoing challenges of invasive species control.
In 1902, red mangroves were brought to Hawaii with an apparently practical purpose. Their tangled roots could hold soil in place, reduce erosion and stabilise shorelines around vulnerable coastal areas. At the time, the trees seemed like a useful solution for an island environment shaped by waves, storms and shifting sediment. More than a century later, that decision has produced a very different legacy. Red mangroves have spread across wetlands and estuaries, forming dense thickets that block waterways, alter water flow and crowd out native plants. They are now affecting habitats used by endangered Hawaiian waterbirds, including the aeʻo and ʻalae keʻokeʻo.
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