Measures of vegetation cover – its extent, condition and degree of fragmentation, can be used as substitutes for monitoring biodiversity (e.g. animal habitat, plant assemblages and genetic diversity). They can also be used to monitor the impact of pressures on biodiversity (e.g. land clearing, spread of dryland salinity and sediment build up). Because different types of vegetation absorb, transmit and reflect solar radiation in characteristic ways, vegetation cover can be monitored using remote sensing relatively frequently, over wide areas of the earth's surface and at relatively fine resolutions.