Coastlines are the narrow interface between the Earth's three great realms - the land, the atmosphere and the oceans. This is the zone where diversity of life is often concentrated, bringing together some organisms from the sea, other species from the land, and those that occur only in the thin inter-tidal strip itself. Processes operating in one domain affect the other. For example, the ocean temperature affects that on land, while the land provides nutrients to the oceans. Conditions along coasts are also influenced by tidal changes and particularly by weather, such as wind and the waves and currents driven by atmospheric circulation. The coastal area of the Hardap Region is characterised by extreme aridity, frequent fog and southerly winds. Offshore, the cold Benguela Current and its associated upwelling system is rich in nutrients and brings cool conditions to the coast. The coastline consists largely of sandy beaches with salt pans and gravel plains inshore. The Hardap coastal area falls within the Namib Naukluft Park. It is scenically dramatic and economically important, a combination which is well illustrated by Sossusvlei - one of Namibia's top tourist attractions that attracts huge numbers of tourists every year. The area comprises some of the harshest parts of the Namib Desert, almost exclusively dominated by the dune sea which consists of shifting sands dropping straight into the sea. There is no significant rocky shore and little fresh water. Although the sand sea is an inhospitable, highly mobile environment it supports a number of highly specialised plants and animals. Further to the east, the Naukluft Mountains also fall within the Hardap section of the Namib Naukluft Park. Here, there is much more variety, both in terms of habitats and in terms of the plants and animals which live there.