The negative impact of human activity on wetlands and mangroves. This also highlights how human activity and industrial production affects a particular ecosystem and the mechanisms and processes, which contributes to these negative outcomes.
Mangrove wetlands, an example of an ecosystem at risk, exist in areas subject to periodic inundation by saline water, between 25°N and 25°S of the equator. Mangrove wetlands occur only within the limits of the tidal range, therefore they are confined to coastal areas. This ecosystem is characterised by anoxic soils and dominated by mangrove trees. Mangroves wetlands support extensive estuarine food webs, act as a nursery for fish and marine invertebrates, provide shoreline stability, and prevent erosion. Negative human impacts on the mangrove wetland ecosystem can be examined within a framework that focuses on the interaction between the four spheres of the biophysical environment.
Human modifications of the atmosphere in mangrove wetlands includes the changing wind patterns caused by the inappropriate location and design of buildings adjacent to the wetlands, and poorly designed walkways within them. The construction of boardwalks in mangrove wetlands can be detrimental if they are constructed in a linear fashion. This leads to wind tunnelling, which eventually results in mangrove dieback.
The characteristically high levels of humidity found in mangrove wetlands can be affected by any alterations to water flows. For example the straightening of Powell’s creek in the Bicentennial Park wetlands in the 1950s dramatically altered drainage patterns. The removal of mangrove wetlands, for example along the Parramatta River, has reduced the gases contributed by mangrove trees through transpiration.
Human impacts on the hydrosphere include altered salinity levels, increased magnitude of tidal inundation, and increased phosphate levels. The health of mangrove wetlands depends on the influx of both fresh water and saline water, however when dramatic changes in salinity levels or tidal inundation occur ecosystem functioning is affected. Large-scale changes in salinity may be due to runoff from areas of dryland salinity, imbalance of fresh water caused by flooding, or altered drainage patterns changing the ratio of salt water to fresh water. This often results from the construction of seawalls, bund walls, roads, and bridge embankments, or the emplacement of dams, reducing fresh water outflows.
Variations in salinity can kill mangrove trees, and have detrimental affects on other estuarine organisms such as air-breathing molluscs. If the magnitude or frequency of tidal inundation increases, as a result of to increased runoff following heavy rain, or altered drainage into the wetlands, the functioning of the ecosystem is put under increased stress. Pneumatophores cannot survive a long period of inundation, and this may lead to mangrove dieback.