San Cristobal is the easternmost island in the Galapagos Archipelago. The island is also one of the oldest of the Galapagos Islands geologically. Its name comes from the patron saint of seafarers, St. Christopher. The island also has a second name of Chatham Island, derived from William Pitt, 1st Earl of Chatham.
San Cristobal has an area of 558 km², making it the fourth largest island in the Archipelago. The highest point of the island rises to 730m. The island is composed of three or four fused volcanoes, all extinct. A small lake called El Junco is the only source of fresh water in the Galapagos Islands. This availability of fresh water is what led to the early settlement of San Cristobal making the island home to the oldest permanent settlement of the Islands and the island where Darwin first landed ashore in 1835.
San Cristobal is the most fertile island of the archipelago and is the second most populated after Santa Cruz, with approximately 6000 people. The capital of the Archipelago, Puerto Baquerizo Moreno, lies at the south-western tip of the island. A penal colony was built on San Cristobal Island in 1880 for prisoners from mainland Ecuador. This later turned into a military base for Ecuador and export center for the island’s products including sugar, coffee, cassava, cattle, fish and lime.
Puerto Baquerizo Moreno is home to many government offices, an Ecuadorian navy facility and an airport with daily flights to the mainland. The majority of inhabitants make their living in government, tourism, and artisanal fishing. San Cristobal is also home to the largest of the fishing fleets in Galapagos.
The largest fresh water lake in the archipelago, El Junco is located in a crater in the highlands of San Cristobal, in the southern half of the island. The lake harbors a large population of bird life but reaching it requires a short uphill walk. Nearby, La Galapaguera is a breeding station and sanctuary for giant tortoises.
Isla Lobos is a tiny islet just off the coast of San Cristobal. The islet is a seasonal nesting location for blue-footed boobies, although it is named for the colony of sea lions and fur seals that are sometimes present there. Frigatebirds have also nested there in recent years. The islet has a tranquil and scenic atmosphere, and is a great place for snorkelling with marine iguanas and spotting sally lightfoot crabs which line the lava rocks along the shoreline. Blue-footed boobies, red footed boobies, Nazca boobies and swallow-tailed gulls are also a common sight. Less commonly seen birds such as yellow warblers and numerous species of finches occasionally appear at various points around San Cristobal. There is also a chance that visitors might see white-cheeked pintail ducks, common gallinules and the Chatham mockingbird.
Manta rays, sea turtles and sharks are often spotted in the waters surrounding the island. Across the various dive and snorkel sitesn large numbers of pelagic fish species, Galapagos sharks, eagle rays, sea turtles are also regularly spotted.
San Cristobal is home to many highly-endangered plants including miconia bushes and endemic tree ferns. Its vegetation includes the endemic pink and white flower Calandrinia galapagosa, the endemic yellow flower Lecocarpus darwinii, and trees such as guayacan (Lignum vitae) and Matazarna.
Due to the intensive use of the highlands of San Cristobal, the presence of goats and aggressive introduced plants species such as the guayaba and blackberry, however, many native and endemic plant species have been decimated. In the late 1990s, a complete survey of the island was initiated to locate rare and endangered plant species. While many of the most endangered species were located, their survival remains questionable without reducing the population of feral ungulates, primarily goats. Work is being done to reduce their impact, however, and almost 50% of feral goats have been removed from San Cristobal Island.
San Cristobal is also extremely susceptible to the potential of new introductions of exotic and sometimes aggressive species due to the existence of an airport and a port. Several of the more serious introductions have occurred first in San Cristobal, including the black fly (Simulium bipunctata), which was introduced in 1990. This fly has caused problems for farmers in the highlands where it is most common. It sucks blood from both humans and farm animals, leaving a poison that in some cases has resulted in the death of animals.