The Republic of Ireland (Irish: Poblacht na hÉireann),[a] usually shortened to simply Ireland (Éire [ˈeːɾʲə] (listen)), is a country in northwest Europe consisting of 26 of the 32 counties situated on the island of Ireland. The capital and largest city is Dublin. The country has a population of around 5.1 million, with 2.1 million of them living in the Greater Dublin Area. Ireland is a sovereign state, a unitary state, and a parliamentary republic. It shares its only land border with Northern Ireland, a section of the island's north which is classed as part of the United Kingdom. It is otherwise surrounded by the Atlantic Ocean, with the Celtic Sea to the south, St George's Channel to the southeast, and the Irish Sea to the east.
The Irish Free State was created with Dominion status in 1922, following the Anglo-Irish Treaty. In 1937, a new constitution was adopted, in which the state was named "Ireland" and effectively became a republic, with an elected non-executive president. It was officially declared a republic in 1949, following the Republic of Ireland Act 1948. Ireland became a member of the United Nations in 1955. It joined the European Communities (EC), the predecessor of the European Union (EU), in 1973. The state had no formal relations with Northern Ireland for most of the 20th century, but the 1980s and 1990s saw the British and Irish governments working with Northern Irish parties to resolve the conflict that had become known as the Troubles. Since the signing of the Good Friday Agreement in 1998, the Irish government and Northern Irish government have co-operated on a number of policy areas under the North/South Ministerial Council created by the Agreement.
The state extends over an area of about five-sixths (70,273 km2 or 27,133 sq mi) of the island of Ireland (84,421 km2 or 32,595 sq mi), with Northern Ireland constituting the remainder. The island is bounded to the north and west by the Atlantic Ocean and to the northeast by the North Channel. To the east, the Irish Sea connects to the Atlantic Ocean via St George's Channel and the Celtic Sea to the southwest.
The western landscape mostly consists of rugged cliffs, hills and mountains. The central lowlands are extensively covered with glacial deposits of clay and sand, as well as significant areas of bogland and several lakes. The highest point is Carrauntoohil (1,038.6 m or 3,407 ft), located in the MacGillycuddy's Reeks mountain range in the southwest. River Shannon, which traverses the central lowlands, is the longest river in Ireland at 386 kilometres or 240 miles in length. The west coast is more rugged than the east, with numerous islands, peninsulas, headlands and bays.
Ireland is one of the least forested countries in Europe. Until the end of the Middle Ages, the land was heavily forested. Native species include deciduous trees such as oak, ash, hazel, birch, alder, willow, aspen, elm, rowan and hawthorn, as well as evergreen trees such Scots pine, yew, holly and strawberry trees. The growth of blanket bog and the extensive clearing of woodland for farming are believed to be the main causes of deforestation. Today, only about 10% of Ireland is woodland, most of which is non-native conifer plantations, and only 2% of which is native woodland. The average woodland cover in European countries is over 33%.
According to Coillte, a state-owned forestry business, the country's climate gives Ireland one of the fastest growth rates for forests in Europe. Hedgerows, which are traditionally used to define land boundaries, are an important substitute for woodland habitat, providing refuge for native wild flora and a wide range of insect, bird and mammal species. It is home to two terrestrial ecoregions: Celtic broadleaf forests and North Atlantic moist mixed forests.
Agriculture accounts for about 64% of the total land area. This has resulted in limited land to preserve natural habitats, in particular for larger wild mammals with greater territorial requirements. The long history of agricultural production coupled with modern agricultural methods, such as pesticide and fertiliser use, has placed pressure on biodiversity.