The island's geography comprises relatively low-lying mountains surrounding a central plain, with several navigable rivers extending inland. Its lush vegetation is a product of its mild but changeable climate which is free of extremes in temperature. It was covered by thick woodlands until the Middle Ages. As of 2013, the amount of land that is wooded in Ireland is about 11% of the total, compared with a European average of 35%.[7][8] There are twenty-six extant mammal species native to Ireland.[9] The Irish climate is influenced by the Atlantic Ocean and thus very moderate,[10] and winters are milder than expected for such a northerly area, although summers are cooler than those in continental Europe. Rainfall and cloud cover are abundant.
The names Ireland and Éire derive from Old IrishEriu. This in turn comes from the Proto-Celtic*Iveriu (compare WelshIwerddon), which is also the source of Latin Hibernia. Iveriu derives from a root meaning 'fat, prosperous'.[12][self-published source?]
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