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This popular center island is the third largest of the main islands of Hawai`i with a total land area of 596.7 square miles. Two shield volcanoes formed the island, Wai`anae and Ko`olau. Ko`olau means “windward” in the Hawaiian language.

The eastern half of the Ko`olau Volcano slid into the Pacific Ocean in prehistoric times leaving the western half of the original volcano which now comprises the Ko`olau Range, home to the Oahu Forest National Wildlife Refuge which protects some of the last remaining intact native forests on O’ahu.

O’ahu is the most densely populated island in Hawai`i. Click here to see a map published by American Forests of urban expansion on O’ahu from 1992-2005.

The Hawaii Statewide Assessment of Forest Conditions (SWARS) solicited public input on the critical issues in the urban forest at the Hawaii Conservation Alliance’s Conference in Honolulu in 2009. Click here to see some of the questions and answers.

Places to Visit

Hawai`i State Parks

Lyon Arboretum University of Hawai`i

Foster Botanical Garden

Bishop Museum

Protected Places

Oahu Forest National Wildlife Refuge

Honolulu Division of Urban Forestry


DLNR: State of Hawaii Forest Reserve System Oahu

United States Geological Survey

U. S. Forest Service

City and County of Honolulu Interactive GIS Maps and Data

Hawaii Coastal Geology Group

Water and Weather

Hawaii Association of Watershed Partnerships

Ko’olau Mountains Watershed Partnership

DOFAW Hawaii Watersheds Q&A

National Weather Service

Earth Observatory: Little Islands Big Wake


CTAHR Hawaii Forestry Extension

Hawaii Forest Industry Association

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