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Australian Academy of Science, Becker House, Canberra. Friday 16 December 1994
Dr John Finnigan
I am going to speak on land-based inputs into the coastal zone. I am going to sneak up on this topic via an introduction to the CSIRO Coastal Zone Program and the intersection of that program with the purposes of LOICZ. I will expand a little bit on the parts of the CSIRO program that are directly concerned with land-based inputs into the coastal zone - how the stuff actually gets into the water from the land - and then I will conclude by looking in more detail at one particular land-based input that is now causing an acute problem in Australia.
Most of the problems in the coastal zone in Australia are really coming from the increasing population and the pressure that puts on coastal resources. For example:
Just to make that a little bit more graphic, we can compare this satellite picture of Darwin in 1972, with a second picture taken in 1988 over which time the population of Darwin went from 39,000 to 71,000, an 85 per cent increase. In Darwin, urban areas have encroached on one of the largest mangrove provinces in Australia leading to a wide-scale clearing of those mangroves - and also exposure of acid soils which I will say a little bit more about later.
Another coastal city, in the fastest growing state in Australia, is Perth - the capital of Western Australia - where there is a quite different system. It is a city expanding along the sandy coastal plain to the west of an escarpment and having particular problems of transport of contaminants through very porous soils into the ground water and also into the ocean. Perth is a very low-density city. Eighty per cent of Perth consists of detached houses and it has seen a population growth of more than 50 per cent over the same period as Darwin.
Along with increased population comes increased industry creating jobs but also bringing the problems of sewage disposal, urban stormwater disposal and competing pressure for resources. There was a distinguished city planner in South Australia in the late 1900s who said that the whole problem of town planning was that of connecting bums to the sea. Quite a perceptive statement that sums up much of Australian coastal urban infrastructure development this century.
These pressures occurring in the Australian coastal environment have unique features in the global context. John Parslow was talking about the kinds of concentrations of chlorophyll that are observed around the Australian coastal margin. We generally have very nutrient-poor waters on the global scale. We do not have significant marginal upwelling and we have very low delivery of fresh water and nutrients from the continent itself into the coastal zone. That delivery itself is very episodic. We have particular provinces of sea grasses, mangroves and corals which are not seen elsewhere in the world and a very diverse maritime fauna. This unique ecosystem is the centre of population: 85 per cent of the Australian population now lives in the coastal zone.
These problems impact on a zone that is sufficiently unique in its biological, geomorphological and oceanographic character that the solutions must be, to a larger degree, home grown.
A significant feature of all these problem areas is that they are estuaries or embayments. This is also where most people live and where flushing and exchange with the open ocean is limited. Estuaries are also the richest biological ecosystems of the coastal zone and play a vital part in maintaining fisheries and providing a livelihood for many of the people living in the coastal zone.
HENCE the focus on the catchment-estuary system.