More than 100 years ago, red mangroves were introduced to Hawaii; Now teams are trying to eradicate them from nearly 2 miles of waterways to restore wetlands and protect endangered birds.

Hawaii environmental teams have launched a major effort to remove invasive red mangroves from nearly two miles of waterways in Kailua. The project aims to reverse more than a century of environmental damage and protect endangered native waterfowl. The multi-year project, announced August 25, 2026 by the Hawaii Department of Land and Natural Resources (DLNR), will focus on thick stands of red mangrove (Rhizophora mangle) that have spread through streams that feed the Kawainui and Hamakua wetlands on Oahu’s windward coast. The work is funded by joint grants from the National Fish and Wildlife Foundation and the National Oceanic and Atmospheric Administration (NOAA). It brings together the DLNR Division of Forestry and Wildlife (DOFAW), the University of Hawaii Pacific Cooperative Studies Unit, and Hui o Koolaupoko (HOK), a nonprofit environmental organization based in Kailua. Community involvement is a key part of the plan. Project leaders are asking volunteers, community groups, schools and private landowners to help field teams remove young mangrove plants and seed pods from affected waterways. The first physical removal work is scheduled to begin on Saturday, September 26, 2026. Crews will initially focus on Kawainui Stream between Kawainui Neighborhood Park and the Hamakua Street Bridge.

An invasive tree that changed Hawaii’s wetlands

Red mangroves are not native to the Hawaiian Islands. The trees were first brought from Florida to Molokai in 1902 by the American Sugar Company to help control coastal erosion and soil runoff. They subsequently spread rapidly through brackish estuaries, coastal lagoons, and freshwater streams throughout the islands. For more than a century, invasive trees have changed the way water moves through wetlands. Unlike Hawaii’s native coastal plants, red mangroves grow dense networks of wading roots that trap sediment, raise stream beds, slow water flow, and reduce water quality. In low-lying areas like Kailua, blocked drainage can also increase the risk of local flooding during periods of heavy rain. Environmentalists say the changes have seriously damaged important wetland habitats. The thick mangrove canopies push out native plants and eliminate open mudflats that provide important feeding and nesting areas for endangered Hawaiian waterfowl. Birds affected by mangrove expansion include the Hawaiian stilt (aeo), Hawaiian coot (alae keokeo), Hawaiian gallinule (alae ula), and Hawaiian duck (koloa maoli). These birds depend on open, shallow water and clear views to detect predators such as mongooses and feral cats.

Community support is key

Field crews will remove small trees and seed pods before planting native Hawaiian wetland species along cleared stream banks. Native plants can help hold the soil in place and reduce the chances of mangrove seedlings becoming established again. Organizers say long-term community support will be essential because the project covers both public and private land along the waterways. “We are honored to partner with the Division of Forestry and Wildlife to bring the wetland and bird habitat restoration techniques we have developed at Heʻeia State Park back to our hometown,” said Kristen Nalani Kane, Executive Director of Hui o Koolaupoko, in an official statement released by the DLNR. “This is the first of many phases necessary to achieve functional eradication of mangroves from Kailua waterways, and community involvement will be essential to its long-term success.”Scientists involved in the project said restoring the natural flow of water will benefit the ecosystem as a whole, not just native birds. “Removing invasive mangroves is essential to restoring the health and functioning of these wetlands. This project reflects what is possible when agencies and the community work together to create better habitat for Hawaii’s native waterfowl and a more resilient ecosystem for future generations,” said Lailan Uy, a wetland biologist working with the University of Hawaii’s Pacific Cooperative Studies Unit in cooperation with state wildlife authorities.

Long term work needed

The Kailua project builds on previous restoration efforts at nearby Heeia State Park and Kawainui Marsh State Wildlife Sanctuary, the largest remaining wetland on Oahu. Removing mangroves is only the first step. Long-term monitoring will be necessary because mature trees can produce hundreds of pencil-shaped seed pods called propagules. These can float long distances on ocean currents and tides before taking root in muddy areas. Without regular checks and removal of new seedlings, cleared areas can quickly become covered by mangroves again. Monthly community work days are planned from the end of 2026 to 2027, with participation focused on people over 18 years of age. Hui o Koolaupoko coordinators are also working with private landowners along the streams to provide access for removal crews and help ensure the entire two-mile area is covered. By restoring natural water flow and restoring open marsh habitats, conservationists hope to make Oahu’s windward coast more resilient to climate change while creating safer habitats for some of Hawaii’s unique native species.