Relatively low-lying mountains surrounding a central plain epitomise Ireland's geography 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 the 1600s. Today, it is the most deforested area in Europe. Twenty-six mammal species are native to Ireland, with some, such as the red fox, hedgehog and badger, being very common. Others, like the Irish hare, red deer and pine marten are less so.