Guadalupe Island - Ecology

Ecology

Guadalupe Island was a major destination for Russian and American fur hunters seeking the Guadalupe fur seal (Arctocephalus townsendi) in the eighteenth and nineteen centuries, until they were nearly extirpated by 1844. Captain Auguste Duhaut-Cilly reported in 1827 that a Sandwich Islands (Hawaiian Islands) brig "had spent several months there and collected three thousand sealskins". The Northern elephant seal (Mirounga angustirostris) was also ruthlessly hunted for the oil in its blubber. They were thought to be extinct in 1884 until a remnant population of eight individuals was discovered on Guadalupe Island in 1892 by a Smithsonian expedition, who promptly killed seven of them for their collections. The elephant seals managed to survive, and were finally protected by the Mexican government in 1922. All surviving Northern elephant seals share the same male ancestor.

Guadalupe shares the California chaparral and woodlands ecoregion with the Channel Islands of California in the United States, but the island was at one time practically denuded of all plants higher than a few centimeters by the up to 100,000 feral goats.

Originally brought there in the early 19th century by primarily Russian whalers and sealers for provisions when stopping over, the population eventually eliminated most vegetation; the number of goats declined to a few thousand. The main impact of the goat population was before this collapse, about the turn of the 19th/20th century. Naturalist A.W. Anthony wrote in 1901:

"It is directly due to the despised Billy-goat that many interesting species of plants formerly abundant are now extinct, and also that one or more of the birds peculiar to the island has disappeared, and others are following rapidly."

After the crash, the goat population once again grew, this time more slowly, until it had reached the new, lower carrying capacity at maybe 10,000–20,000 in modern times. The island had been a nature conservancy area since August 16, 1928, making it one of the oldest reserves in Mexico. Eradication of the goats was long envisioned, but logistical difficulties such as island size and lack of suitable spots for landing and encamping hunters and material prevented this. As of June 2005, after many years of false starts, the Mexican government has almost completed a round-up and evacuation of the remaining goat population and Guadalupe has been designated a biosphere reserve.

French sea captain Auguste Duhaut-Cilly remarked on the tall trees on the north of Guadalupe Island as he sailed past on January 2, 1827. Of the large tree species on Guadalupe Island (Guadalupe Palm, Guadalupe Cypress, Island Oak, and Guadalupe Pine), there were only old individuals left; California Juniper had entirely disappeared. As the goats ate any seedlings that managed to germinate, no regeneration of trees was possible. Water, formerly plentiful as the common fogs condensed in the forests of the northern end of the island, today only occurs in a few scattered pools and springs. Because the springs were a critical emergency water supply for the human inhabitants, protective measures including goat fences were installed beginning in 2000, allowing new seedlings of many species to survive for the first time in 150 years. Seacology, a non-profit environmental group located in Berkeley, CA, provided funding to the Island Conservation & Ecology Group for the construction of ten fenced exclosures to keep goats out of the most sensitive areas of Guadalupe Island.

Many island or marine species that reside on or near Guadalupe also frequent the Channel Islands, and vice-versa. In stark contrast to the rampant extinction of terrestrial life that happened at the same time, Guadalupe was the last refuge for the Northern Elephant Seal (Mirounga angustirostris) and the Guadalupe Fur Seal (Arctocephalus townsendi) in the 1890s. The island has been a pinniped sanctuary since 1975.

Guadalupe is considered one of the best spots in the world for sightings of the Great White Shark, possibly because of its large population of pinnipeds.