Family: Rhizophoraceae

Origin, Description & Uses
Rhizophora mangle (red mangrove, American mangrove) is native to tropical and subtropical coastlines of southern Florida, across Tropical America, and from western tropical Africa to Angola. It was introduced to Hawaiʻi in 1902 by the American Sugar Company to stabilize mudflats on southwestern Molokaʻi. It is now naturalized across the Hawaiian Islands, including Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, Maui, and Hawaiʻi Island, particularly in saltwater marshes and intertidal zones. This species is easily identified by its distinctive stilt-like prop roots that arch from trunks and branches into the water, allowing it to anchor in soft, unstable sediments. It is commonly used in coastal regions for shoreline stabilization, erosion control, and as habitat that supports fish, shellfish, and other marine organisms. In some regions, it has also been used for fuelwood and coastal protection plantings.

Risks & Threats
Although it provides some ecological benefits, red mangrove is a naturalized species in Hawaiʻi and possesses traits that are cause for concern. It spreads readily in coastal wetlands, where it can alter hydrology, trap sediments, and convert open mudflats into dense mangrove forests. These changes can displace native shoreline plants and reduce habitat quality for native waterbirds and other species that depend on open coastal environments. As a result, it could detrimentally impact tropical island ecosystems that are especially sensitive to shoreline modification. Where possible, choosing native or low-risk alternatives is recommended. In areas where it is already widespread, limiting new plantings and managing expansion into less-affected coastal zones can help reduce further ecological impacts.

High Risk Traits:

• Naturalized & invasive in Hawaii
  
• Forms dense, monospecific thickets
  
• Shade-tolerant seedlings
  
• Tolerates wide range of soils & pH
  
• Self-compatible; produces viable seeds
  
• Hybridizes naturally
  
• Propagules water-dispersed & viable >1 year
  
• Intentionally planted by people
  
• No effective natural enemies in introduced range

Low Risk Traits:

• No spines, thorns, or burrs
  
• Not parasitic or toxic
  
• No fire tolerance; poor coppicing
  
• Not bird-dispersed or animal-dispersed
  
• Controllable with herbicides