Lava flows and ash and cinder falls periodically occur on the Island of Hawaii. Hurricanes were infrequent and mild before 1950, but three severe hurricanes have damaged Kauai since then. Drought tends to be localized. Nearly all streams on wetter slopes of Maui, Big Island, and Oahu are diverted by ditch and tunnel systems or urban channelization. Exotic animals have caused severe grazing and dispersal of exotic plants.
Native plants suffer from severe competition and transformation of soil, water, and fire regimes.
Settlement, agriculture, grazing, urbanization, and re-forestation have transformed most coastal and lowland areas and many upland areas. Conversion of upland and forest areas continues. Coastal and agricultural lands are being further urbanized. Land use changes plus impacts of exotic species are contributing to continuing extinctions. Nearly a quarter of native plants are proposed or listed as threatened or endangered.