Forested watershed

90% of the terrestrial species are endemic (unique to the region), and many are threatened or endangered. Habitat loss and alteration, and the spread of invasive plants have all contribute to extinctions and ecosystem decline. Sea level rise is expected to severely impact low-lying areas, including coastal plants, nesting seabirds, seals, and turtles.

Ocean acidification and coral bleaching will lead to loss of coastal habitats and negatively impact the productivity of fisheries. The productivity of ocean fisheries is anticipated to decline by up to 50% by late century. By late century, under a high emissions scenario, nearly all coral reefs are expected to be severely compromised by ocean acidification. Currently, coral reef cover is at 38%; by late century, the amount is projected to be less than 1%.

Extremely heavy rainfall has become more common in Hawai'i, leading to increased runoff, erosion, and flooding. The number of consecutive wet days and dry days have been increasing in Hawai'i.

Increasing temperatures, an expanding human population, and increased cover of invasive shrubs and grasses, such as common gorse, fountain grass and guinea grass, all contribute to increased risk of wildfire in Hawai'i.

Warmer temperatures and decreased cloud cover in some areas are likely to result in greater evaporation rates, leading to reductions in water supply and increases in demand. Hawai'i has already experienced a trend toward increasing drought conditions during the winter rainy season. Decreased soil moisture increases plant stress, with impacts to agricultural and natural systems.