Hawaii’s 124-year-old red mangroves now threaten native waterbirds and waterways

Representative image of Hawaii from Canva 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. As explained by the Hawaii Department of Land and Natural Resources and research supported by the USGS, the story is a reminder that an introduced species can appear beneficial at first while creating ecological problems that last for generations.A solution imported from elsewhereHawaii’s coastal wetlands have always been dynamic places. Freshwater streams meet the ocean, tides move through mudflats and lagoons, and native plants have adapted to changing salinity and water levels. These...