Biogeography of Hawaii
Biogeography is the study of how geography affects the biological world. Geographic features play a dominant role in shaping Hawaii’s natural world and make it a great place for biogeographic studies. The Hawaiian islands make up the most extensive archipelago on earth. They contain an incredible diversity of terrain, habitat, and climate zones. Because of its continuous formation over the hot spot, Hawaii represents the world’s longest timeline of island formation. Scientists travel through time, as they study this island chain. Hawaii’s extreme isolation has been the foremost influencing factor in the unique evolution of these islands. At right is a world map with Hawaii at the center (as all maps should be.)
Hawaii is the most isolated island group in the world. The nearest continent, North America, is over 2500 miles (4000 km) away. This extreme isolation made it difficult for plants and animals to colonize the islands. The odds of surviving the journey by air or sea is small; making it here and establishing a reproducing population is miraculous. On average, an invertebrate successfully colonized Hawaii once in every 70,000 years, a plant once in every 100,000 years, and a bird once in every million years. At right, an endangered Hawaiian Monk Seal basks on an island beach just like any other tourist.
All of Hawaii’s many plants and animals are evolutionary descendents of colonizers that made it here either by air or by sea. The Kolea, or Pacific Plover, is an annual visitor to Hawaii. It makes long non-stop flights from the Arctic circle every fall and departs in the spring. Unlike the Kolea, most colonizers made it here by accident carried in the air by the jet stream and storm systems or by the ocean currents.
From the desert coastal environments, to the wettest spot on earth, to snow-capped peaks, Hawaii contains one of the most concentrated collections of climates and ecosystems on the globe. A coconut palm-lined beach that receives less than 10 inches (25cm) of rain annually is framed by the arctic-climate, snow-covered summit of Mauna Loa volcano at 13,570 feet (4,136m).
The diverse array of island geography allowed for the island’s biota to adapt to different conditions. Above, a birdwatcher surrounded by giant tree ferns searches the canopy for rare Hawaiian forest birds in a cloud mist rainforest kipuka. Kipuka are isolated stands of forest on older lava flows that are surrounded on all sides by younger and less vegetated lava flows. They are, in effect, islands within islands.
Ten miles upslope from the cloud mist kipuka, as the I’iwi flies, is Lake Waiau. Located near the summit of Mauna Kea at the 13,000 foot (3962m) elevation, it is one of the highest alpine lakes in the world. Once capped with glaciers Mauna Kea’s glacial lake is fed by the melting of the glacial permafrost.
CREDITS – University of Hawaii: World map; Jack Jeffrey: Hawaiian Monk Seal, Kolea; Kirk Aeder: A coconut palm-lined beach; Carl Waldbauer: Cloud mist rainforest kipuka, Lake Waiau