Key Habitats
Seagrasses
Seagrasses are unique marine flowering plants that form dense meadows in shallow, near-coastal areas throughout the South Pacific. Seagrass ecosystems support rich biodiversity, including the endangered green sea turtle and dugong, which hold cultural significance in Polynesia—as does the seagrass itself, which is used in traditional crafts. These habitats are widely threatened by poor water quality; their loss contributes to coastal erosion and biodiversity loss.
Mangroves
Mangrove tree species were not introduced to Polynesia until the 20th century, but mangrove forests are now widespread in brackish coastal waters. While they can be invasive where they replace native seagrass environments, Polynesian mangroves are economically and ecologically valuable in their own right, supporting fisheries and serving as breeding grounds for many species, as well as protecting coastal regions from natural disasters by acting as a physical barrier to wind and flooding.
Coral Reefs
Many Pacific islands are surrounded by shallow-water coral reef belts that support vital fisheries. These habitats are highly vulnerable to bleaching events (expulsion of symbiotic algae that generally often to coral death) caused by rising sea temperatures.
Tropical forests
Much of Polynesia has a tropical climate influenced by south-east trade winds, and the original terrestrial landscape is wet and dry tropical forests. Human intervention for timber and other resource development has gradually converted over 70% of original forests to less-biodiverse secondary forest, grassland, and dry savanna; in Hawaii, 90% of tropical dry forests have been lost.
Most Pressing Issues
Invasive species
Introduced species already outnumber endemics on most Polynesian islands, and many of these have had detrimental effects on native ecosystems. In New Zealand, the introduction of mammals like rats and cats have decimated native flightless bird populations, while the brown tree snake has been similarly destructive to the bird life of Guam.
Ocean Pollution
Marine plastic debris constitute a major threat to global oceans, threatening the health of fish populations and humans who consume them. As a region that is primarily oceanic and dependent on marine food sources, Polynesia is particularly vulnerable to plastic pollution as well as other detrimental ocean pollutants including heavy metals and hydrocarbon residues from fossil fuels.
Climate Change
The smaller, low-lying islands of Polynesia are already vulnerable to weather-related natural catastrophes including cyclones and floods, which will increase in frequency and severity with the warming climate. Rising oceans will also make many of these places uninhabitable due to flooding and saline intrusion, causing displacement of tens of thousands of people over time.
