Assessing the development of newly created habitat for wintering estuarine birds

The term coastal squeeze has been used to describe the process whereby hard flood defences in areas subjected to relative sea level rise constrain the ability of an estuarine system to respond naturally, thus leading to a loss of intertidal habitat, with an associated potential reduction in the carrying capacity of the estuarine system for fish and bird populations. The process of coastal squeeze, coupled with the long-term effects of climate change, has generated the need to create or restore intertidal habitats in estuaries. In Humber Estuary (UK) it is estimated that over 700 hectares of intertidal habitat will be lost due to coastal squeeze and rising sea levels over the next 50 years. In order to address this net loss, a process known as ‘managed realignment’ has been employed as an estuarine habitat management tool, whereby sections of flood defences are moved inland to create or restore intertidal habitat and offset potential losses in carrying capacity. On the Humber, the Paull Holme Strays site, to the east of Hull, has been the first managed realignment site on the estuary to become operational. The site at Paull Holme Strays was breached in September 2003 creating approximately 80 hectares of intertidal habitat. In order to assess the development of the waterbird assemblage at the Paull Holme Strays site, and ultimately the success of the habitat creation technique, monthly ornithological surveys were undertaken in the newly created habitat and on the mudflat fronting the managed realignment site. The analysis of avifaunal usage data at Paull Holme Strays has demonstrated that within 3 years of creation, the new intertidal habitat is capable of supporting at low water, a functional waterbird assemblage of similar composition to that of adjacent existing intertidal areas. At Paull Holme Strays, this has been achieved with little ongoing management of new habitats.