Both these industries are absolutely important economically,' says Dr McPhail, 'but increased loads of sediment and nutrients have the greatest potential to degrade coastal ecosystems. We are also concerned about the effect of agricultural pesticides and herbicides together with heavy metals, hydrocarbons and litter, in particular plastics, coming from cities and towns', he added. The melaleuca wetlands and mangrove forests are areas of high biodiversity with 70 per cent of all inshore fishery species being dependent on these areas for some part of their life cycles. These pressures include the direct removal and damage of mangrove plants, conversion of mangrove lands to other uses, changing water flow and sediment distribution, chronic and catastrophic pollution and the introduction of exotic pests and pathogens. There are good environmental and economic reasons to maintain wetland systems.
Wetlands use their nutrient exchange efficiency as a filter for excess nutrients in run-off water.
The limiting factor for the growth of mangrove forests is the supply of nitrogen and phosphorus, which are potentially deadly to fringing coral reefs. Mangrove forests can efficiently remove these chemicals converting the nutrient to leaf growth. This constant supply of food makes a very stable food chain. If we had no mangroves, this rich mud would wash away with the tides and floods. In its place we would have a boom or bust planktonic system dependent upon ocean tides which are simple, highly reactive and unstable', says Andrew Ballard an environmental scientist at the Authority.