The dubious accolade of being the biggest threat to wader populations, of multiple species, goes to habitat loss, be it by destruction or degradation. This scourge manifests itself in a variety of devastating, human initiated, actions; intertidal reclamation, changes in agricultural practices, drainage, pollution, disturbance, afforestation, dredging, river management and ploughing up of grasslands are some of the more obvious actions that are seriously affecting waders, of all kinds, everywhere. Add to this the background threat of the effect of climate change altering the environment, a rather more chronic problem, which is never far away and you’ll discover that every habitat in which waders exist is under threat in one way or another.
Historically many areas across the world have been drained to provide fertile soil for agriculture as well as for development, road construction, mining and mosquito control, among many others. One of the grandest examples of this is the Fenlands of England which once stretched from Lincolnshire and Norfolk south to Cambridge and which rendered Ely an island when flood waters inundated the land. This area has changed so much that it would now be unrecognisable to anyone who lived in the days before it was drained, the land now comprising flat and fertile fields criss-crossed by drainage ditches to maintain the lower water table. The population of many wader species would have been seriously compromised by the loss of this extensive marshland. Among them the Black-tailed Godwit which was once a relatively common species in the region became extinct as a British breeding bird. As their numbers dwindled their new rarity made them more valuable to the trophy hunters and collectors.
In the 1800’s projects were initiated to drain the massive Everglades swamp in Florida with a view to converting the land to agriculture and development for towns and tourism. Today it receives less than one-third of its historic water flow and the wildlife-rich wetlands are half the size they were even in the 1920s. Greater access to the everglades led to unrestricted hunting when waders and other water birds suffered greatly, especially egrets, which were killed for their glorious plumes. The piecemeal drainage and conversion to agriculture and urbanisation has increased pollution from run off and fertilisers in the water that remains.
Haarlemmermeer (The lake of Haarlem) is one of the biggest, if not the biggest, drainage project ever accomplished. Situated in the Netherlands it once covered over 150 square kilometres and was drained by successive projects finally being dry in 1852. It is thought that around one thousand billion litres of water were removed to drain the lake.
Mangroves are another habitat that waders find of great value for foraging and roosting, and they are under threat across the globe particularly in Asia where they are being converted into agricultural land, aquacultural areas and removed for building development, particularly in the tourism sector. On the other hand, mangroves have been spreading across saltmarshes and tidal mudflats removing vital feeding areas of open mudflats and marsh from the waders’ choice of feeding area. Mangroves are restricted in their range by temperature requirements, as the planet warms they are able to access new areas and invade new coastal marshes and mudflats that are critical to the survival of migrating and wintering waders.
Peat bogs naturally hold a lot of water, and carbon. In order to extract the peat the area needs to be drained and then the peat extracted. The draining of the peat causes greater run off and that water is altered containing augmented suspended material and dissolved organic matter and increases in nutrient and metal content, colour and pH are to be found. Small scale hand dug peat extraction may not have caused too much harm, but the mechanised wholesale destruction of entire habitats in the last thirty years has had a devastating effect, particularly in Ireland where it has been instrumental in the decline in Curlew numbers.
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