r and coastal management
Degradation of habitat can also occur by the altering of water flowing from a river or along a coastline. Many estuarine mudflats exist because for millions of years the rivers have been depositing sediment at their final destination, the sea. But naturally that sediment is also washed away so needs constant replenishment. If a river is dammed or dredged to control the flow, altering its speed and volume, it will inevitably affect the amount of sediment deposited. Damming can reduce the flow to such an extent that the mud flats will simply disappear or at least change their character. Sediments may settle further upstream in slower moving water or be trapped by the dam itself and existing mudflat may erode, the sediment being transported and deposited elsewhere changing the physical form of the flats.
Dredging has the opposite effect where fast flowing water carries larger, heavier sediment which washes away smaller particles preventing them from settling. From a waders point of view deeper faster moving water is far less suitable for feeding than shallow slow-moving or still water.
If the flow of the water is changed it will therefore alter the deposition of the sediment and can change mud flats into sandy flats if the flow increases and vice versa if it is reduced. In addition a change of water level and velocity can render some islands in the middle of rivers, which were hitherto unreachable to land mammals, accessible if water levels drop or they can be washed away if the speed and level increases.
At the mouth of a river, where it meets the sea, the fresh water mixes with the salty sea water and salinity levels are increased. There are creatures in that environment that require the diluted salinity to thrive, so, if river flows are reduced the salinity increases and some life forms will not be able to survive. These victims may well be those that the waders are feeding upon again reducing the suitability of the habitat for waders.
River flow will also impact upon floodplains where periodic inundation is the main driver of habitat survival. Many waders rely on floodplains and their existence is under threat where the flooding has been reduced or halted altogether.
Changes in the physical aspects of a coastline caused by large projects, such as the development of a port, or smaller objects, like groins or barriers, can dramatically change the drift of sediments along the shoreline. This can impact on the formation and evolution of flats and spits which are often extensively used by foraging waders. In one instance in New Zealand a new port development changed the currents to such an extent that silt deposits to one side of the port all but ceased, this led to the erosion of that portion of the coast. Some important coastal lagoons which existed there, which had been separated from the sea by the sediment were lost and swallowed by the sea as the barrier diminished thus eradicating not one, but two vital wader habitats.
If predicted warnings are correct, the impact of climate change would be devastating to coastal environments as previously intertidal areas would remain permanently under water and with human structures along much of the coast, which we would obviously protect, there is no natural place for the intertidal area to advance into and mud flats would become an endangered environment.
Existing ports are being developed and expanded, often meaning that large areas of mud are removed to allow ships to enter the area. The same thing happens in small bays, which are often shallow and ideal feeding grounds for waders where marinas are constructed for privately owned boats and yachts.
We all love a beach, and being by the sea is the preferred place to live for many of us. In addition it is where many of us choose to spend our holidays. The result is that all those people wanting to be beside the sea need places to live, or stay temporarily, and the entire infrastructure that goes with that.
Coastal towns tend to spread along the coast rather than inland increasing the area of beach front th