The Icelandic ?rofabard? soil erosion features

Abstract

Soil erosion and desertification are severe problems in Iceland. Erosion processes are numerous, and more than one can occur at each site, resulting in many erosional forms. Erosion forms and an erosion severity scale are the basis for a recent national survey of erosion in Iceland. One of the most distinctive erosion forms in Iceland is an erosion escarpment, termed ‘rofabard’ in Icelandic. Rofabards are formed in thick but non-cohesive Andosols that overlie more cohesive materials such as glacial till or lava. The relatively loose Andosols beneath the root mat are undermined, creating escarpments, or rofabards. The rofabards retreat as a unit, with a fully vegetated and rich ecosystem on top but leaving barren desert in their place. Rofabards are common within a 20 000 km2 area. The Agricultural Research Institute and Soil Conservation Service erosion database suggests that erosion associated with rofabards has denuded 15 000 –30 000 km2 of land that was previously fully vegetated and had fertile Andosols, but is now mostly desert. Erosion rates associated with rofabards are reported as the loss of vegetated land with Andosol mantle, measured as hectares per square kilometre per year. This measure of erosion has more meaning for Icelandic landscapes than the traditional tonnes per hectare per year. Estimated losses of Andosol cover in rofabard areas for the whole country are currently about 230 ha a−1. This rate is about 10 times lower than the rate needed to cause estimated losses of Andosol mantle in rofabard areas since settlement, 1125 years ago. During peak years of soil erosion, losses were probably several thousand hectares per year, but the erosion rates slowed down as extensive Andosol areas have become barren deserts. Copyright © 2000 John Wiley & Sons, Ltd.