Channel Islands National Park

Ecology
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Channel Islands National Park
Channel Islands National Park (courtesy, NPS)

Which is more important—the land or the ocean? For many plants and animals of the Channel Islands, life is not possible without both land and sea. Pelicans fish for anchovies from the ocean, but nest on the dry bluffs of West Anacapa. Low-growing sand verbena needs the sandy soil of San Miguel Island to grow, but it also needs salt from the ocean air to thrive. Giant kelp fastens its rootlike hold-fasts on the shallow rocks of islands' near-shore reefs, yet this seaweed also needs the nutrients from the deep ocean.

Isolation from the mainland and the mingling of warm and cold water currents in the Santa Barbara Channel help form the Channel Islands' unique character. The plants and animals are similar to those on the mainland, but thousands of years of isolation in unique island environments have resulted in size, shape, or color variations among some plants and animals. All of the larger islands are home for the island fox, a close relative of the mainland's gray fox. But because it evolved in isolation, the island fox is no larger than a house cat. These foxes prey upon deer mice that are slightly larger than their mainland relatives. Both creatures are well adapted to the harsh island environment.

Remoteness from the mainland has buffered the islands from the rapid changes wrought by modern man. While most mainland tidepools are practically devoid of life because of heavy human use, abalone, sea urchins, sea anemones, and limpets thrive in the islands' intertidal areas. White-plumed sea anemones still cover underwater rocks at San Miguel, and vivid purple hydrocorals filter water for food near Santa Cruz Island. Though used by fishermen and sport divers, and subject to mainland water pollutants, the kelp forests of the Channel Islands harbor great numbers of plants and animals.

During the last Ice Age the northern Channel Islands were part of one vast island geologists call Santarosae. Sea level was then much lower, and large areas of today's sea bed were dry. The northern islands were then linked together, though probably not connected to the mainland. Later, when the great continental ice sheets melted, the islands were separated.

During the Pleistocene era, a dwarf species of mammoth roamed Santarosae, and pine and cypress forests stood on several islands. Today, the fossilized remains of dwarf mammoths on San Miguel and Santa Rosa, and the forests of brittle sand castings, known as caliche (pronounced kah-lee-chee) that are found on San Miguel remind us that the islands were very different long ago. Some plants and animals have developed special adaptations over time to cope with the isolated environment—others remain unchanged. The giant coreopsis is found on all five park islands and on the coastal mainland. Its more common name, tree sunflower, suggests its size and trunk-like stem. Its bright yellow blossoms are sometimes visible from the mainland during the winter and spring.

The introduction of non-native plants and animals to an island ecosystem can devastate native species. One such exotic is a tenacious South African species of iceplant, which found its way to Santa Barbara Island before 1900. Highly salt tolerant, it thrives in acid soil by capturing moisture from sea breezes. It subsequently leaches salt into the soil, producing concentrations of salt that few native plants can tolerate. Today, the iceplant spreads its thick mats over much of the island. Introduced livestock, food, animals, and pets have similar impacts on island environments. Escalating feral sheep, hog, cat, and rabbit populations led to damage to—and sometimes elimination of—native plants and animals. The National Park Service seeks to restore these native populations where possible.

All plants, animals, rocks, and other natural, archaeological, and historic features on the islands and in the nautical mile of waters surrounding them are protected and may not be disturbed, destroyed, or taken. Even dead vegetation may not be gathered or burned. Please keep in mind that others will follow you, so "take only memories, leave only footprints" when visiting the islands. Be careful with fire. Because of the high risk of fire that could destroy plant communities, no open fires are permitted on the islands. Discharge of firearms and fireworks is not allowed in the park or within the one-nautical-mile seaward boundary of ocean within the state ecological reserves. Please take home any trash that you bring in. Report accidents or unusual incidents immediately to the National Park Service or U.S. Coast Guard.


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