Timothy F Smith, CSIRO Sustainable Ecosystems
Michael Doherty, CSIRO Sustainable Ecosystems
prepared for the 2006 Australian State of the Environment Committee, 2006
The suburbanisation in coastal areas creates two forms of pressure on the natural environment.
The first pressure is described as direct pressure or where there is an initial impact on the environment as areas are developed and settled. Direct pressures include:
- displacement (for example, land clearing) of resident coastal terrestrial, aquatic and marine ecosystems for infrastructure (for example, buildings, roads, bridges, parks, promenades and piers, marinas, swimming areas, canals, dams and water supply infrastructure, electricity and phone lines, storm drains and guttering, sewerage works, rubbish tips)
- destruction of natural, cultural and Indigenous heritage in coastal areas and coastal waters
- destruction of highly fertile coastal landscapes—both in relation to biodiversity and in relation to agriculture
- the development of coastal areas and exposure of acid sulphate soils .
The second pressure is ongoing pressure, which involves managing the impact of human settlements. For example, ongoing pressures in coastal settlements may result from an increase in impervious surface cover (for example, roads) leading to greater and more intense runoff, which then has the potential to transport increased volumes of nutrients, pollutants and refuse into waterways. Clearly, the sheer volume of waste to be absorbed or otherwise disposed of also increases markedly with population density and the problems facing existing coastal urban areas (such as Sydney or the Gold Coast) are being replicated to varying degrees along Australia’s coast. Coastal settlement adjacent to estuaries (for example, intermittently closed and open lagoons) may also affect nutrient cycling and other biogeochemical processes that are important to those ecosystems, due to increased pollutant loads (that may also release into aquatic food chains). Indirect pressures or impacts of suburbanisation of coastal areas can also result from:
- sewage disposal
- other solid waste disposal
- air pollution from increased concentrations of vehicles
- point and diffuse source pollution of coastal freshwater surface and groundwater bodies
- increased concentrations of recreational fishing and boating impacting on aquatic ecosystems
- impacts on wildlife from increased collisions with vehicles, and sound and visual pollution
- increased pollution from industries servicing increased populations.
Because the suburbanisation of coastal landscapes is an ongoing process (ABS 2001), it can be argued that the continued clearing of coastal and hinterland areas for new residential developments is the greatest continuing threat to habitats. Harvey and Caton (2003) discuss in greater detail many of these management issues that are facing coastal Australia and the underlying ecosystem processes that influence management.
Fundamentally, the issues that we grapple with in striving to make Australia’s major cities and towns more sustainable are the same ones that we grapple with in managing the broader coastline. The greater the density of people per hectare in settled areas, the greater the challenge of absorbing the impacts created by those people in situ. On the other hand, diffuse settlements have a more widespread impact, particularly considering that Australians have one of the highest per capita ecological footprints in the world. Should people be concentrated into existing settlements? Is it a case of density versus sprawl? These classic urban planning dilemmas are of equal importance to the management of Australia’s coastal settlements as the demand to live on the coast steadily grows.
Like most ecological issues, the uniqueness of the local environment will dictate the likely impacts of continued coastal urbanisation and ways to manage or mitigate those impacts. The evolution of local tenure, planning and zoning has largely been based on landuse history and settlement patterns, which in turn reflect local resource opportunities and constraints. In the past, coastal national parks were commonly created from Crown land. These areas of Crown tenure were generally unsuitable for agriculture and other forms of economic production and hence many of these areas, while rich in biodiversity and of immense conservation value, are biased toward the less fertile parts of the landscape. The majority of fertile and productive coastal landscapes are in freehold title and, while many of these areas have been cleared in the past for agriculture, many important natural areas (such as habitats) remain in freehold title. These areas are highly valuable habitat for many declining or threatened native marsupials such as koalas, bandicoots and gliders, as they prosper and persist best in fertile landscapes. It is in these areas that increasing pressure for coastal development exists, and many are the basis of local controversies and court cases (for example, the koalas in the Port Stephens area in New South Wales and the Mahogany Glider in South East Queensland). Similarly, suburbanisation has spread to some of our most highly productive agricultural lands, taking them out of productive use and there is also the continued pressure for development on the remaining agriculturally productive coastal areas. On the eastern coast of northern Australia, this has potential implications for water quality entering the Great Barrier Reef. Furthermore, not only does the shift in landuse from agricultural production to suburbanisation alter the landscape and local economies, but also the social structures of those regions.
In other areas, coastal development is encroaching into fire-prone areas of coastal heath, forest and shrubland, as for example in the Margaret River region in Western Australia. As well as destroying primary habitats, these types of coastal settlement have increased vulnerability to wildfire. In response, more bushland is cleared as a firebreak around the new settlements, which leads to increased pressure on surrounding national parks authorities to burn more frequently. Alternatively, there is no response until a fire occurs, resulting in a public ‘blame game’. Pressure to develop freehold land can lead to inappropriate planning decisions and the cumulative impact of decisions made on a case-by-case basis can result in significant and permanent changes to coastal landscapes. The suburbanisation process is not only confined to coastal locations, it is also a pattern manifesting in the hinterland regions of Australian capital cities, and also in ‘tree change’ areas.
Many of Australia’s government institutions (at all levels) have been set up to address one group of issues or sector (for example, health). Due to the complexity of natural processes in the coastal zone, combined with the interdependencies of the ‘sea change’ phenomenon with other social processes (for example, the decline of quality of life in the city suburbs), a systems approach to addressing the coastal population growth is a way forward. While potentially difficult within the current bureaucratic structures, this approach provides a mechanism to identify and manage direct and indirect consequences of a particular issue as well as the direct and indirect drivers of that issue; as a result, a systems approach allows targeted interventions for maximum impact.
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