[Return to The Sanctuary Main Page]   The Natural Environment and Value Sanctuary History Natural Environment The Humpback Whale Hawaiian Cultural Program Exploring the Sanctuary The Hawaiian Islands Humpback Whale National Marine Sanctuary is actually a series of five marine protected areas distributed across the Main Hawaiian Islands. The total area of the sanctuary is about 1,400 square miles. Encompassing about half of the total sanctuary area, the largest contiguous portion of the sanctuary is delineated around Maui, Lana`i and Moloka`i. The four smaller portions are located off the north shore of Kaua`i, off Hawai`i's Kona coast, and off the north and southeast coasts of O`ahu. While this description of the sanctuary's natural environment and human use is generalized for the sanctuary as a whole, it is important to note that upon more detailed inspection, each of the five sanctuary areas has its own distinct natural character and social significance. The waters around the main Hawai`ian Islands of Kaua`i, O`ahu, Hawai`i, Maui, Moloka`i, Lana`i, and Kaho`olawe constitute one of the world's most important North Pacific humpback whale (Megaptera novaeangliae) habitats and the only place in the U.S. where humpbacks reproduce. Geology The Hawaiian Islands formed one by one as the Pacific Plate of the Earth's crust moved northwestward over a stationary "hot spot." At the hot spot, magma from deep within the Earth periodically pushes through the crust to the surface, forming an island. Over millions of years, the Pacific Plate has worked like a very slow conveyor belt, moving islands away from the hot Because it is still over the hot spot, volcanic activity is still observed on the Big Island. Here, a spectacular display of molten lava is pouring into the ocean off the Southern coast of the Big Island. spot and providing fresh areas of oceanic crust over the hot spot so that new islands can emerge. This hot-spot phenomenon explains why the islands get older as one travels northwestward from the Big Island (the youngest island). The oldest parts of the Big Island are estimated to be no more than half a million years old, while Maui, O`ahu and Kaua`i are about 1, 3 and 5 million years old, respectively. Because the Big Island still resides over the hot spot, volcanic activity is still observed there, but the movement of the Pacific plate continues, and a new undersea volcano (Lo`ihi) appears to be growing into an island off the Big Island's southeast coast. Climate and Oceanography Hawai`i is famous for its comfortable climate. Air temperatures over sanctuary waters throughout the state rarely exceed 90 degrees F in the warm season (May through September) and rarely dip below 65 degrees F during the cool season (October through April). The main climate controls in Hawai`i are latitude, the Pacific Ocean and altitude. Lying between 19 and 22 degrees north latitude, the Main Hawaiian Islands are on the edge of the tropics and within the area where trade winds blow northeasterly about eight days out of ten. Because of the islands' low latitude, the longest and shortest days of the year differ by only about two hours. The Pacific Ocean supplies moisture to the air, and, because of its high heat-storage capacity, keeps temperatures within a relatively narrow range. Most differences in temperature from place to place in Hawai`i result primarily from altitude, where cooler areas are typically found at higher elevations. Rainfall is the one climatic feature in Hawai`i that is highly variable. Kaua`i's Mount Wai`ale`ale, where average annual rainfall is around 450 inches per year, is one of the wettest spots on Earth. However, at the sanctuary headquarters in Kihei, Maui, average annual rainfall is only about 15 inches per year. The wettest time of year for most of Hawai`i is during the The underwater crater known as Molokini Crater is a striking example of a nearshore coral reef. Molokini is a favorite snorkeling and diving spot for Maui visitors and residents. cooler months, from November through February, but the Kona Coast of the Big Island, where the southeastern portion of the sanctuary is located, experiences a peak in rainfall during the warmer months of March through August. In general, average annual rainfall over sanctuary waters is between 15 and 60 inches per year. Ranging from about 70 and 80 degrees F, the surface waters of the sanctuary are relatively warm. However, water temperatures at the deepest depths of the sanctuary (around 600 feet) can be as cold as 40 degrees F. The large-scale surface current patterns in the Hawaiian Islands generally go from east to west, but winds and tidal flows add to their complexity. [top] Marine Ecosystems With its boundaries including waters from the shoreline to depths of 600 feet in many areas, the sanctuary encompasses a variety of marine ecosystems, including seagrass beds and coral reefs. Much of the sanctuary has fringing coral reefs close to shore and deeper coral reefs offshore. Hawai`i's coral reefs are noted for their isolation and endemism. Over 25% of all Hawai`i's reef animals are endemic, meaning that they are found nowhere else on earth. In Hawai`i's fringing reef ecosystems, corals and coralline algae are the dominant reef-building organisms. The corals found on the sanctuary's fringing reefs include, table coral (Acropora cytheria) rice coral (Montipora capitata), lobe coral (Pavona duerdeni), corrugated coral (Pavona varians), mushroom coral (Fungia scutaria), lace coral (Pocillopora damicornis), antler coral (Pocillopora eydouxi), These two species of fish, the Moorish Idol (Zanclus cornutus) and the Milletseed Butterfly fish (Chaetodon miliaris), can be seen amongst the spectacular corals found within sanctuary waters. cauliflower coral (Pocilopora meandrina), finger coral (Porites compressa) and plate coral (Porites rus). Other important components of the fringing reef ecosystem include algae (brown, red and green), marine invertebrates (shrimp, lobster, crabs and sea urchins) and fish (parrotfish, wrasses, damselfish, surgeonfish, goatfish, jacks and sharks). Endangered Hawai`ian monk seals and threatened green sea turtles are also important members of the sanctuary's fringing reef community. The deeper reefs lie in the "twilight zone" of the sanctuary below 200 feet. These deep-reef ecosystems have their own unique assemblage of corals, algae and marine invertebrates, many of which are depth-adapted versions of species found at shallower depths. Deep-reef fish include squirrelfish, soldierfish, surgeonfish, snappers and emperors. Endangered Hawai`ian monk seals and threatened green sea turtles also frequent the sanctuary's deeper reefs. Human Uses and Economic Value of the Sanctuary People use the resources found within the sanctuary in a variety of ways. Native Hawaiians have long had close relationships with their marine environment. Nowadays, the marine area included in the sanctuary is used extensively for ocean recreation, fishing and shipping. In sanctuary waters off of Maui, for example, commercial tour operations feature whalewatching, sportfishing, parasailing and snorkeling, while commercial fishing, cruise ships and commercial shipping use the same area. One of the main purposes of the sanctuary is to work with government agencies and the private sector to ensure that these activities are conducted in ways that have the least possible impact on humpback whales and their habitat. The sanctuary's goal of protecting humpback whales and their habitat is very important for the continued success of Hawai`i's whalewatching industry. A recent study estimates that commercial whalewatching tours in Hawai`i support as many as 390 jobs and generate as much as $27 million annually in local revenues. Through its management activities, the sanctuary actively protects the humpback whale's significant economic contribution to the islands. References Gulko, d. 1998. Hawai`ian Coral Reef Ecology. Honolulu: Mutual Publishing. Juvick, S.P. and J.O. Juvick. 1998. Atlas of Hawai`i, 3rd Edition. Honolulu: University of Hawai`i Press. Utech, D. 1999. Valuing Hawai`i's Humpback Whales: The Economic Impact of Humpbacks on Hawai`i's Ocean Tour Industry. Oahu: NOAA, Hawaiian Islands Humpback Whale National Marine Sanctuary. [top] Revised by the HIHWNMS web team on March 10, 2003. URL: http://hawaiihumpbackwhale.noaa.gov/about/natural_environ.html.