Rapa

Trapped at the end of the world; an ecological collapse; a microplate with a new family of crustaceans

I. Map Boundaries: 20 to 30 degrees South, 108 to 117 degrees West

II. Country: Chile (Region V—Valparaiso)

III. Overview

More than 2,300 miles from South America and 1,400 miles from the nearest Polynesian island, nine-mile-wide Easter Island, or Rapa Nui, is remote, so remote that only one influx of people is believed to have settled the island about 900 CE. Once settled, the colonists were likely trapped, setting the stage for one of the most famous human-caused ecological collapses.

Easter is home to more than 900, 50-foot-tall, 250-ton statues carved from the volcanic rock found on the island. These were erected between the 10^th and 16^th centuries and once lined roads leading from the volcanic quarry to other spots on the island. In addition to the statues, the society created ceremonial shrines and the only written language in Oceania. Caves around the coast contain paintings of deities, birds, and fertility symbols.

The grasses and shrubs found when the islands were first seen by Europeans were not the original vegetation. Pollen in swamps indicates the existence of a giant palm and 20 other tree species. The palm was gone by 1450, and other large trees by 1650. Deforestation began around 1280, and resulted in erosion and changes to agricultural practices. Around 1400, islanders began to occupy the uplands and began a labor-intensive gardening method known as stone mulching to decrease evaporation and release nutrients. As wood became scarce, more than 1,000 stone buildings were constructed, some of which were chicken houses. The last statue was carved in 1680. Diamond (2005 and 2007) believes that Easter Island, poor in nutrients and located at the south edge of the tropics, was more fragile than other Polynesian islands and more vulnerable to human impacts. This led to deforestation, loss of palm sap as a food source, switching to grasses and sedges as fuel, establishment of stone mulching, and an abandonment of statue carving (Diamond 2007). Extinctions were not limited to palm trees. There were at least 25 species of seabirds, of which eight to ten no longer breed. There were at least six species of land birds in four families which are now extinct. With the extinction of the trees, it is likely that insects, land snails, and land birds were also affected (Steadman 1995).

From a geologic standpoint, Easter Island sits atop the Sala y Gomez submarine ridge, which trends eastward from the East Pacific Rise. Just to the west of Easter Island are two seamounts that do not reach the surface, Pukao and Moai, and three volcanic fields, Ahu, Umu, and Tupa (Haase, Stoffers and Garbe-Schonberg 1997). The island contains a number of volcanoes and 70 vents. Lava flows are as young as 2,000 years in age (Global Volcanism Program, Smithsonian 2011). The southwestern volcano, Rana Kau, contains a water-filled crater and a ceremonial village on the rim of the crater beneath a cliff. Nearby are the site of fossils of the palm trees that became extinct as islanders cleared the woods. The volcano on the eastern tip, Poike, is known for petroglyphs and standing moai. Terevaka is the youngest volcano, having erupted about 400,000 years ago. Rana Raraku, located on the lower slopes of Terevaka, contains a crater lake and slopes containing scattered moai. Raraku was the quarry for all the island’s statues.

To the northwest of Easter Island is the Easter Island microplate, formed as the Nazca and Pacific plates move away from one another. During a series of submersible dives to hydrothermal vents, the Census of Marine Life project discovered a new family of crustaceans, the squat lobsters, or ‘yeti crab.’ The animal was found at depths of 2,000 m, feeding on hydrothermal vent animals.

IV. Terrestrial Ecoregion

Tropical and Subtropical Moist Broadleaf Forests of the Oceania Biome

111. Rapa Nui and Sala y Gomez Subtropical Broadleaf Forests. The 50 inches of annual rainfall, subtropical latitude, and winter rainy season should be indicative of broadleaf forest vegetation, and indeed the original flora consisted of palms and broadleaf species. The Jubaea palm was present until the 17^th century but it now extinct. It is believed deforestation from felling and burning killed off the long-lived palm trees, and imported rats, which fed on the fruit, were the cause of the extinction. Today the island is covered with grasses and shrubs. There are four terrestrial birds and three marine birds, along with four endemic ferns still present.

V. Freshwater Ecoregions

Australia and Pacific

827. Rapa. The island has freshwater crater lakes but no surface streams.

VI. Marine Ecoregions

Eastern Indo-Pacific Realm, Easter Island Province

163. Easter Island

VII. World Heritage Sites

Rapa Nui National Park. Nominated to the World Heritage List for a powerful, imaginative, and original tradition of monumental architecture, free from any external influence. The park includes the entire island surrounding the settlement of Hanga Roa. Near Hanga Roa is the rock art site of Ana Kai Tangata. To the south is Rana Kau volcano, and to the northeast is Ahu Akivi, with seven standing moai looking toward the sea. All other moai look inland from the sea. At Ana Te Pahu, crops were grown in sunken lava tube caves. To the east are the volcanoes Poike at the eastern tip and Rana Raraku, where the moai were quarried and from where a network of roads led to the rest of the island. Ecoregion OC111.

VIII. References

Abell, Robin et al. 2008. Freshwater Ecoregions of the World: A New Map of Biogeographic Units for Freshwater Biodiversity Conservation. BioScience 58:403-414.

Bahn, Paul G. 1996. Easter Island. Page 190 In: Brian M. Fagan, ed. The Oxford Companion to Archaeology. Oxford University Press.

Census of Marine Life. 2005. Yeti Crab. www.coml.org/print/discoveries/species/kiwa_hirsuta (accessed 5/1/11).

Diamond, Jared. 2007. Easter Island Revisited. Science 317:1692-1694.

Diamond, Jared. 2005. Collapse: How Societies Choose to Fail or Succeed. Penguin Books.

Eyewitness Travel: Chile and Easter Island. DK Publishing, 2011.

Global Volcanism Program, Smithsonian Institution. http://www.volcano.si.edu/ (accessed 5/1/11).

Haase, Karsten M., Peter Stoffers and C. Dieter Garbe-Schonberg. 1997. The Petrogenetic Evolution of Lavas from Easter Island and Neighboring Seamounts, Near-ridge Hotspot Volcanoes in the Southeast Pacific. Journal of Petrology 38:785-813.

Lewis, Krista. 2010. Did They Fail? Could They Choose? Science 327:413-414. Review of Questioning Collapse: Human Resilience, Ecological Vulnerability, and the Aftermath of Empire. Patricia A. McAnany and Norman Yoffee, eds. Cambridge University Press, 2010.

Olson, David M. et al. 2001. Terrestrial Ecoregions of the World: A New Map of Life on Earth. BioScience 51:933-938.

Schenkman, Lauren, ed. 2010. Sacred Roads. Science 328:957.

Schultz, Patricia. 2003. 1,000 Places to See Before You Die. Workman Publishing.

Spalding, Mark D. et al. 2007. Marine Ecoregions of the World: A Bioregionalization of Coastal and Shelf Areas. BioScience 57:573-583.

Steadman, David W. 1995. Prehistoric Extinctions of Pacific Island Birds: Biodiversity Meets Zooarchaeology. Science 267:1123-1131.

Walder, Rebecca. 2006. Americas and the Caribbean. In 501 Must-Visit Destinations. Bounty Books.

World Heritage List. http://whc.unesco.org/en/list (accessed 5/1/11).