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March 25, 1999

A weekly feature provided by scientists at the Hawaiian Volcano Observatory.


Hawai`i's Environment Benefits from Geographic Isolation

One common saying in the real estate business is that location is everything. This is particularly true from both geological and biological standpoints here in Hawaii. The Hawaiian hot spot has produced one of the most isolated island chains in the world, with some benefits not often appreciated. One of them is the natural quarantine imposed by more than 3000 km (2,000 miles) of open ocean.

Hawaii's reputation for having a healthy environment is dependent on this natural quarantine. Many noxious plants, animals, diseases, and disease vectors that occur commonly in other parts of the world never reached the islands because they were unable to cross the open ocean. Those that were brought here either intentionally or accidentally have wreaked havoc on native ecosystems--in most cases because endemic plants and animals that make the island's biota so special never evolved natural defenses against the alien invaders.

One example is the impact that introduced predators, diseases, and mosquitoes had on the decimation of Hawaii's unique native forest birds. Avian malaria and pox virus transmitted by the night-biting southern house mosquito, Culex quinquefasciatus, and direct predation by introduced rats, cats, and mongooses, have decimated most lowland native birds. What has been left are the more disease-resistant and predator-evasive non-native birds like the mejiro, cardinals, mynas, and doves.

At Hawai`i Volcanoes National Park, we typically see yearly epidemics of avian malaria and pox in native honeycreepers between September and December--the time of year when Culex mosquito populations reach their peak. One commonly finds sick or dead `apapane and `amakihi in backyards in Volcano or along trails and roads. Most of these birds suffer from severe anemia caused by the malarial parasites and frequently have large tumors caused by avian pox virus on their feet and legs. Since these diseases are transmitted by mosquito bite, native birds can be infected with both at the same time, leaving them so ill that they are unable to forage or escape from introduced predators.

Laboratory studies have shown that some high elevation honeycreepers, like the `i`iwi, have a fatality rate of up to 90 percent after exposure to a single infective mosquito bite. These diseases have relatively little effect on bird populations in other parts of the world, but they are as pathogenic in Hawaiian birds as ebola virus in humans. As a result, some of the island's most interesting and spectacular native birds, such as the scarlet `i`iwi and the rare and elusive 'akiapola`au, are now found only in cold, high elevation forests where they are above the current range of mosquitoes.

Can something similar happen to the island's human population? The answer unfortunately is "yes." The Hawaiian people were decimated by the introduction of European diseases, such as measles. In more recent times, island residents have suffered from periodic epidemics of dengue virus--a tropical disease that causes high fever and flu-like symptoms. The last major outbreak occurred on O`ahu during World War II, when servicemen returning from the South Pacific infected localized populations of the introduced mosquito, Aedes egypti. The insects, in turn, spread the infection to residents. Before the outbreak was controlled by expensive door-to-door efforts to eradicate the mosquito vector, more than 1,500 island residents were taken ill.

Hawaii's quarantine regulations and restrictions on importing plants and animals are intended to protect us from catastrophes like this. Unfortunately, the speed and global nature of modern transportation places us only one arrival away from accidental introduction of a new pest that might erode our quality of life. To learn more about these threats, we invite you to visit the Hawaii Ecosystems At Risk website (www.hear.org), maintained jointly by USGS-Biological Resources Division, University of Hawai`i, and the National Park Service.

Eruption Update

The eruption of Kilauea Volcano from the Pu`u `O`o vent continued unabated during the past week. Lava flows from the vent through a network of tubes and enters the ocean near Kamokuna. The public is reminded that the ocean entry areas are extremely hazardous, with frequent explosive activity and occasional collapse of the new land. Recently, a videographer filmed the explosive activity following the collapse of the bench on March 8. The video clip was shown on national and international news broadcasts and caused excited viewers to check on the safety of their relatives and friends in Hawai`i.

Three earthquakes from the south flank of Kilauea Volcano were reported felt on March 18. At 11:42 a.m., a magnitude 3.3 earthquake was felt in the `Ainaloa and Mauna Loa Estates subdivisions. Nineteen minutes later, at 12:01 p.m., a magnitude 4.0 earthquake was felt by residents of Hilo and Puna. Another magnitude 4.0 earthquake was felt at 12:52 p.m. by residents of Hilo, Papaikou, and Puna. All three earthquakes were located 14 km (8.4 mi) southeast of the summit of Kilauea Volcano at depths between 6.4 km (3.9 mi) and 9.1 km (5.4 mi).

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Updated: 25 Mar 1999