Extract only - complete publication at www.jncc.gov.uk/worldwaterbirds Waterbirds around the world A global overview of the conservation, management and research of the world's waterbird flyways Edited by G.C. Boere, C.A. Galbraith and D.A. Stroud Assisted by L.K. Bridge, I. Colquhoun, D.A. Scott, D.B.A. Thompson and L.G. Underhill EDINBURGH, UK: THE STATIONERY OFFICE Extract only - complete publication at www.jncc.gov.uk/worldwaterbirds © Scottish Natural Heritage 2006 First published in 2006 by The Stationery Office Limited 71 Lothian Road, Edinburgh EH3 9AZ, UK. Applications for reproduction should be made to Scottish Natural Heritage, Great Glen House, Leachkin Road, Inverness IV3 8NW, UK. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN 0 11 497333 4 Recommended citation: Boere, G.C., Galbraith, C.A. & Stroud, D.A. (eds). 2006. Waterbirds around the world. The Stationery Office, Edinburgh, UK. 960 pp. Names used for geographical entities do not imply recognition, by the organisers of the Waterbirds around the world conference or other supporting organisations or governments, of the political status or boundaries of any particular territory. Names of territories used (and any alternatives) are included solely to help users of this publication apply information contained within this volume for waterbird conservation purposes. The views expressed in papers included within this volume do not necessarily represent views of the editors or the organisations and governments that supported the conference and this publication. Cover photography: Whooper Swans Cygnus cygnus arriving at Martin Mere, England. Photo: Paul Marshall. (www.paulmarshallphotography.com) Copyright of all photographs used in this publication resides with the named photographers. Waterbirds around the world Loss of shorebird habitat as a result of mangrove incursion due to sea-level rise and urbanization Phil Straw1 & Neil Saintilan2 1 Avifauna Research & Services, PO Box 2006, Rockdale Delivery Centre, NSW 2216, Australia. (email: [email protected]) 2 Centre for Environmental Restoration and Stewardship, Australian Catholic University, Mackillop Campus. PO Box 968, North Sydney, NSW 2059, Australia. (email: [email protected]) Straw, P. & Saintilan, N. 2006. Loss of shorebird habitat as a result of mangrove incursion due to sea-level rise and urbanization. Waterbirds around the world. Eds. G.C. Boere, C.A. Galbraith & D.A. Stroud. The Stationery Office, Edinburgh, UK. pp. 717-720. ABSTRACT In a study of 134 sites used by roosting shorebirds in 18 estuaries Most migratory shorebird species require areas of open habitat in New South Wales, Lawler described the roosting habitat of such as tidal flats and salt-marshes where they can forage, rest five species with respect to a range of variables. Of the ground and moult. The expansion of mangroves into shorebird feeding roosts, of which there were 93, only two were within 10 m of and roosting habitats due to sea-level rise and increased sedi- vegetation over 5 m tall, and 83% were at least 30 m distant mentation is presenting a significant problem in closed situa- from trees 5 m tall. Ninety percent of ground roosting sites were tions such as estuaries in Hong Kong, Taiwan and eastern further than 10 m from 2 m high trees and bushes. Beaches Australia. Seaward invasion of mangroves onto tidal mudflats as accounted for 55% of roost sites, salt-marshes for 15%, a result of excessive sedimentation caused by poor watershed mangrove trees for 19%, and artificial structures for 11%. management is affecting shorebird feeding areas. Landward Studies of the Hunter Estuary in New South Wales have invasion of mangroves in response to sea-level rise is affecting revealed that shorebirds abandon diurnal roost sites on sand spits salt-marsh areas important as shorebird roosting and feeding and river-training walls where terrestrial predators, such as habitat. Options for management intervention, such as the foxes, might be able to approach under the cover of darkness controlled removal of accreting mangrove seedlings and (Clarke & van Gessel 1983, Geering 1995, Straw 2000). The saplings from key shorebird feeding grounds, as well as the sites chosen at night are flooded back-swamps: usually salt- restoration and creation of mudflat and salt-marsh habitat, are marsh or shallow lagoons where predators would be reluctant to discussed. stalk roosting shorebirds and where they would be more obvious. As there are few studies of nocturnal roost sites, it is SHOREBIRD HABITAT REQUIREMENTS unknown how widespread this practice is. Most migratory shorebirds prefer to feed on open areas of undis- turbed mudflats where they have a clear view of the approach of THE MANGROVE ENVIRONMENT avian or terrestrial predators. Roosting sites are also selected to Mangroves form an important part of the coastal ecology in provide an open view and easy escape in case a predator southern Asia and throughout Australasia, together with approaches. Only under certain circumstances, where they have sea-grasses and open tidal flats on the seaward side and salt-marsh no alternative, will shorebirds utilize habitats close to tall vege- communities on the landward side of the mangrove belt. The width tation or structures that obscure their view. of mangrove woodland varies from a few metres to several kilo- In a survey of 63 inter-tidal flats in nine New South Wales metres, depending on the latitude and coastal topography. The estuaries on the east coast of Australia, Lawler (1996) deter- most extensive forests tend to exist in the tropics along shallow mined estuarine features which related to abundance in the coastlines where there are many species of mangrove, whereas in feeding habitat of six species. The Bar-tailed Godwit Limosa temperate regions only one or two species occur. lapponica selected large, low-lying flats for feeding; Whimbrel The widespread loss and degradation of mangrove forests Numenius phaeopus favoured mangrove-lined flats in high-sedi- throughout South-east Asia and on the eastern coast of Australia ment regimes; and Far Eastern Curlew N. madagascariensis and are well documented. Logging and conversion for aquaculture are Pacific Golden Plover Pluvialis fulva favoured large complexes among the most frequently cited causes in South-east Asia, while of flats. Common Greenshanks Tringa nebularia frequented the conversion of mangrove forests into waterfront residential and feeding areas of any size, provided they were wet, nutrient-rich resort accommodation has been one of the main causes in and mangrove-fringed. Grey-tailed Tattlers Heteroscelus Australia. Over the years, awareness regarding the ecological and brevipes were more likely to feed adjacent to mangroves and on economic importance of mangroves has grown. As a result, many flats with some ground cover. authorities are engaged in efforts to restore this valuable resource, During high tide, when tidal flats are submerged, shorebirds and this is reflected in the increasing number of publications and require roosting sites such as beaches, sand spits, salt-marshes, workshops dedicated to the subject (e.g. JAM 1994, Khemnark and structures such as infrequently used jetties, barges, rock 1995, Field 1996). In New South Wales, the removal of mangroves walls and oyster platforms. A few species, such as the Grey- without a licence now carries heavy penalties, with fines of tailed Tattler and Whimbrel, frequently roost on exposed AUS$ 55 000 for individuals and AUS$ 100 000 applying for branches of mangrove trees. corporations (Diver 2003). Any licences that are granted usually One of the most significant findings of Lawler (1996) was require the planting of at least one mangrove for every one the extent to which most shorebirds avoided trees while roosting. removed in a place where they have a high likelihood of survival. 717 Waterbirds around the world Unfortunately, many mangrove restoration projects move both a seaward and landward direction. Recent studies have immediately into planting mangroves without determining why shown that mangroves have invaded large areas of salt-marsh and natural recovery has not occurred (Lewis 1998). Mangrove open tidal mudflats, two types of habitat utilized by shorebirds. planting efforts have been conducted both in degraded former This situation is most pronounced in areas of rapid coastal devel- mangrove areas as well as in areas where mangroves have not opment where coastal wetlands, including tidal mudflats, have previously occurred. Various South-east Asian countries have been substantially reduced. The accretion of mangroves onto tidal carried out large-scale planting of mangrove seedlings on inter- mudflats is thought to be a result of increased silt loads and tidal mudflats (which cannot be considered “restoration”) as part nutrient levels due to uncontrolled development and soil erosion of well-intentioned mangrove restoration programmes. Though in upstream catchment areas. Mangroves follow such fertile areas limited in success, these efforts have resulted in afforestation of of mud accretion, and their establishment in such environments significant tracts of open tidal flats over the past decade, may lead to a reduction in the extent of open tidal flat habitat substantially reducing the area of inter-tidal mudflat habitat available to shorebirds (Augustinus 1995). Mangrove expansion (Erftemeijer & Lewis 2000). Land-ownership issues appear to in a landward direction over the past five decades may be attrib- play a major role in targeting mudflats for such planting uted to a rise in sea level, which has exposed upper inter-tidal programmes, as mudflats are “easily” accessible (with no-one environments to mangrove colonization. Wilton (2001) demon- claiming ownership), while access to abandoned shrimp ponds strated that while salt-marsh losses in recent decades have been in former mangrove areas - which should be the real target for greatest in urbanized estuaries, the component of loss due to restoration - usually involves complicated legal claims over land mangrove encroachment is relatively constant between estuaries, ownership.