Several ecological reserves lie on the flanks of Hualālai. The Puʻu Waʻa Waʻa forest sanctuary was established in 1992 (along with the Laupahoehoe sister reserve on Mauna Kea) as a testbed for long term ecological research about Hawaiian moist forest and dry forest biomes, and lies within a mile of the volcano's summit on its northwestern flank. Elevation differs from sea level near the coastal edge to near the summit. Median annual rainfall is about . Plentiful lava flows from the 19th century provide unique niches for vegetative and soil growth in the region. The southern section of the reserve, closest to the summit, has been split into a bird sanctuary.