Haleakala, rising from the sea to a 10,000 foot summit, and exposed to both the windward moist tradewinds and leeward drying air, has a variety of natural ecosystems. From the top; the alpine aeolian mountain summit zone seems barren at first glance. The porous, rocky, dry surface has wide temperature range between day and night. Only a few species survive this tough environment. Silverswords stand out in the sweeping open landscape.
Subalpine shrublands cover broad areas below the alpine zone. Native shrubs are dominant. Locally nene are conspicuous in the shrublands.
Lower down, on the windward slopes with rainfall of 120 to 400 inches annually, rainforest prevails. Above 3,000 feet elevation the rainforest is largely native species with ohia and koa forests forming a closed canopy. This is habitat of the native Hawaii honeycreepers.
Below the shrub zone dry forest occupies the drier leeward slopes, with less than 60 inches of rain. Fire and alien ungulates have devastated most of Maui's dry forest zones. Only small patches are found within the park.
The Oheo stream ecosystem crosses several life zones. This stream, with its entire length within the national park, is one of very few completely natural riparian habitats in Hawaii. Native fish and shrimp are stream residents.