The island’s geography comprises relatively low-lying mountains surrounding a central plain, with several navigable rivers extending inland. The island has lush vegetation, a product of its mild but changeable oceanic climate, which avoids extremes in temperature. Thick woodlands covered the island until medieval times. Today, the amount of land that is forested in Ireland is just one third of the European average of 35%. There are twenty-six extant mammal species native to Ireland.
Gaelic Ireland emerged some time in prehistory and lasted until the early 17th century. The island was converted to Christianity from the 5th century onward. Following the Norman invasion in the 12th century, England claimed sovereignty over Ireland. However, English rule did not extend over the whole island until the 16th–17th century Tudor conquest. This led to the colonization of northern Ireland by settlers from Britain. In the 1690s, a system of Protestant English rule was designed to materially disadvantage the Catholic majority and Protestant dissenters, and was extended during the 18th century. In 1801, Ireland became a part of the United Kingdom. A war of independence in the early 20th century was followed by the partition of the island, creating the Irish Free State, which became increasingly sovereign over the following decades, and Northern Ireland which remained a part of the United Kingdom. Northern Ireland saw much civil unrest from the late 1960s until the 1990s. This subsided following a political agreement in 1998. In 1973, both parts of Ireland joined the European Economic Community.