Are Mangroves Native or Invasive?
by Nick Hammond on Jan 29, 2022
Mangroves are a unique group of trees and shrubs that inhabit tropical and subtropical coastlines around the world. Their status as native or invasive species has been debated, depending on the location.
Mangroves are considered native to the tropical and subtropical coastlines between 25°N and 25°S latitude. This includes extensive mangrove forests found along the coasts of the Americas, Africa, Asia, Australia and islands of the Pacific and Indian Oceans. The native range reflects their evolutionary adaptations to warm, saline habitats based on regional climate patterns and geographic connectivity.
Some major native mangrove habitats include the southeastern coasts of North, Central, and South America, including the Florida Everglades. Mangroves are also native to East Africa and Madagascar, as well as South Asia from India to Southeast Asia and islands of the Pacific such as New Guinea. Australia contains over 11% of the world's mangrove forests, particularly along the northern and eastern coasts.
While mangroves evolved in tropical and subtropical habitats, they have been introduced to some additional areas by human activity. Mangroves have been planted for coastal stabilization, aquaculture, and forestry outside their native range.
Regions where mangroves have been introduced include Hawaii, Singapore, parts of the Middle East like Qatar and the United Arab Emirates, and some islands in the Caribbean. In these areas, mangrove stands are usually small and fragmented compared to native forests. Their non-native status shapes how mangroves are managed in terms of conservation and invasion risk.
Mangroves possess certain biological traits that allow them to spread rapidly and outcompete native species once established in an area. These invasive characteristics include:
- Rapid growth and early maturity. Mangroves are fast growing trees that can begin reproducing within 5-10 years.
- Prolific seed production. Mature mangrove trees produce abundant propagules that are dispersed by ocean currents.
- Ability to colonize disturbed areas. Mangrove seedlings can take hold in muddy shoreline habitats where native vegetation has been removed.
- Physiological adaptations. Mangroves are highly tolerant of saline water, flooding, low oxygen soils, and tropical climates.
These advantages give mangroves a competitive edge over native plants that did not evolve under the same conditions.
The invasive status of mangroves depends on the region. In Hawaii, the introduced red mangrove is considered a noxious invasive species. Mangrove removal efforts are underway to protect Hawaii's native coastal plants.
However, in most of their native tropical range, mangroves provide essential ecosystem services and habitat. Clearing mangroves where they are native can damage fisheries, increase erosion, and degrade water quality.
So in summary, mangroves are native to warm coastal habitats globally but can exhibit invasive traits and compete with native flora where they have been introduced. Their long-term invasive impacts and management continue to be researched and debated.
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