Coastal population growth exerts strong pressure on coastal land by increasing the need for both agriculture and housing, and land-use demands often come at the expense of natural habitats and native species. Agriculture reduces biodiversity by replacing native communities with monospecific crops, and urbanisation causes direct habitat loss. Remaining vegetation is then affected by diffuse pollution, habitat fragmentation, competition from weeds, predation by invasive pests, and Allee effects associated with catchment land-use activities (see Native vegetation and habitat).

Trends in coastal development and land use can be observed through change in the number of registered properties, known as cadastral parcels. Nationally, since 2011, the highest overall increase in the number of urban parcels has occurred nearest the coast (Figure COA2). This was the case in New South Wales, Victoria, Queensland and Western Australia, where population growth was greatest, while other states showed little trend relative to distance from the coast. The opposite patterns were seen for peri-urban (on the outskirts of cities and towns) and rural parcels, indicating that these types of properties are being replaced with urban development near the coast, but less so inland.

The largest change for rural and peri-urban to urban land use was seen in Victoria, approximately 30 kilometres from the coast (Figure COA2). This corresponds with an increase in population in these areas (Figure COA1), and is driven by land-use change in the outer suburbs of Melbourne. In contrast, expansion of some other large coastal cities is occurring parallel to the coastline, rather than inland or equidirectional from the city centre. In Perth, for example, development has expanded north and south along the coast, and future plans continue expansion in these directions (see Perth and Peel Urban Land Development Outlook). Growth immediately adjacent to the coast was also seen in Queensland.

Surveys of 48 estuaries in New South Wales between 1999 and 2006 found that 60–80 per cent of catchment land has been cleared for agricultural, residential or industrial development (Roper et al. 2011). In coastal south-east Queensland, urban density and extent increased with the clearing of vegetation from 1972 to 2010 (Lyons et al. 2012). The western catchments of south-east Queensland are generally in poor condition, having suffered extensive clearing of riparian vegetation (Healthy Waterways 2015). The central and southern catchments are in fair condition, whereas the condition of northern catchments ranges from fair to excellent (Healthy Waterways 2015).

Increased coastal development amplifies most pressures discussed in this report, as well as a suite of other pressures related to urbanisation. Urbanisation of the coast, for example, creates the need for stormwater drainage, and an estimated 3000 gigalitres of storm water (the equivalent of 2.1 million Olympic-sized swimming pools) are produced in Australia each year (SECRC 2015). Most of the pressures discussed in the remainder of this chapter can be considered to increase, either linearly or disproportionately, with increases in coastal population and development.