Whichever modelling is used, global warming is likely to lead to rises in sea-level. The precise timing, duration and extent are, however, not yet known. On rocky coasts where the slope of intertidal habitats is not uniform, there will almost certainly be profound changes in area of available habitat. In New South Wales, Australia, most intertidal rocky shores are backed by a steep vertical cliff and the bulk of the space is fairly horizontal. If all other processes stay equally intense throughout the tidal range as they are now, when sea-level is higher there will predictably be a smaller amount of space available. This prediction was tested by projecting areas onto the shore to represent increases in sea-level of 10, 20 or 50 cm (in a tidal range of maximum 2m). The densities of various species were then calculated using the new areas and consequences from known ecological interactions (e.g. competition for space and food) determined. In addition, species-area curves were calculated for present shores and for the areas projected for the chosen increases in sea-level. In most cases, decreased area of habitat due to a rise in sea-level would result in loss of species and densities greatly exceeding current carrying capacity. Finally, some species would be under great threat because they do not thrive on vertical compared to the currently mostly horizontal habitats on local shores. Some of the relevant issues for conservation will be considered.
