When the [Iceland] was first settled, it was extensively forested. In the late 12th-century, Ari the Wise, described it in Íslendingabók as "forested from mountain to sea shore". Permanent human settlement greatly disturbed the isolated ecosystem of thin, volcanic soils and limited species diversity. The forests were heavily exploited over the centuries for firewood and timber.Deforestation, climatic deterioration during the Little Ice Age and overgrazing by sheep imported by settlers caused a loss of critical topsoil due to erosion. Today, many farms have been abandoned. Three-quarters of Iceland's hundred thousand square kilometres are affected by soil erosion, eighteen thousand square kilometres so seriously as to be useless.Only a few small birch stands now exist in isolated reserves. The planting of new forests has increased the number of trees, but does not compare to the original forests. Some of the planted forests include introduced species.The tallest tree in Iceland is a sitka spruce planted in 1949 in Kirkjubæjarklaustur; it was measured at 25.2 metres (83 ft) in 2013.

Global Warming.