Natural versus artificial- wetlands and their waterbirds in Sri Lanka M.G. Bellio a, * , R.T. Kingsford a , S.W. Kotagama b a SBEES – School of Biological, Earth and Environmental Sciences, University of New South Wales, NSW 2052, Australia b FOGSL – Field Ornithological Group of Sri Lanka, Department of Zoology, University of Colombo, Sri Lanka article info Article history: Received 7 May 2009 Received in revised form 2 August 2009 Accepted 8 August 2009 Available online 12 September 2009 Keywords: Functional wetland ecology RAMSAR Agricultural impacts Artificial wetlands Hydrological regime abstract As natural wetlands have disappeared around the world, artificial wetlands have increased. We found interesting differences in waterbird communities of two natural (Bundala Ramsar site) and seven artifi- cial wetlands (irrigation tanks, salt ponds, rice paddies) in south-east Sri Lanka. Eight species exclusively used natural and one species artificial wetlands. Migratory species (shorebirds 64%, terns 47%) dominated species’ richness of natural lagoons, with densities of shorebirds 3–6 times greater than on artificial wet- lands. Contrastingly, resident species (dabbling ducks, gallinules) contributed most to the diversity (59%) and density of waterbirds on artificial irrigation tanks. Cattle egrets dominated waterbird density (>70%) of rice paddies. Waterbird communities reflected physical and chemical character of wetlands: natural wetlands were shallow (<2 m) and saline (EC > 1000 msm 1 ) compared to deep (>2 m) and freshwater (EC < 110 msm 1 ) artificial wetlands. Artificial inputs of water drained into the natural Embilikala lagoon changing its physico-chemical profile and disrupting the natural seasonal drying. Consequently its water- bird community was similar to artificial irrigation tanks, with shorebird species particularly impacted: densities half that of the other natural lagoon. Artificial salt ponds had similar physico-chemical proper- ties to the natural Bundala lagoon and a similar waterbird community. Even though artificial wetlands supported waterbirds, they were not adequate replacements for loss of natural wetlands, favouring some species. Imposed hydrological stability degraded habitat quality for migratory shorebirds on one of our Ramsar site lagoons. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Natural wetlands continue to decline globally (Dahl, 1990; Hollis, 1992; ANCA, 1996), with increasing human development. As a result, waterbirds are declining around the world (Davidson and Stroud, 2006; Cao et al., 2008; Nebel et al., 2008) because of their dependency on wetlands for survival, reproduction and recruitment (Haig et al., 1998; Guadagnin and Maltchik, 2007). Agriculture and aquaculture have expanded at the expense of wetlands (Revenga et al., 2000; Galbraith et al., 2005) but have cre- ated artificial wetlands (Hoeg, 2000). Natural wetlands occupy only about 6% of the earth’s surface, compared to agro-ecosystems covering about 25%, excluding Greenland and Antarctica (Mitsch and Gosselink, 2000). Many artificial wetlands are created to convey or hold water (e.g. reservoirs, paddy fields, salt evaporation ponds) but are used by waterbirds (Fasola and Ruiz, 1996; Rehfisch, 1994; Masero, 2003). A key question is whether such artificial wetlands replace natural wetlands (Tourenq et al., 2001; Ma et al., 2004). Waterbirds can be used to examine this question because different species (e.g. piscivores, herbivores) sample habi- tat complexity, with diversity and abundance reflecting wetland functional value (Short and Burnham, 1982). A matrix of natural (coastal lagoons) and artificial (paddy fields, salt evaporation ponds and irrigation tanks) wetlands exist within a large irrigation and agricultural settlement scheme in the dry zone of southern Sri Lanka, the Kirindi Oya Settlement Project (KOISP) (Fig. 1). The coastal lagoons are part of a Ramsar site, whose hydrology is potentially degraded by agricultural develop- ment (Piyankarage et al., 2004; Smakhtin et al., 2004). We compared species richness, abundance and waterbird community composition between natural and artificial wetlands. Natural wetlands were expected to have a higher ratio of migratory to resident species because their limnological and hydrological characteristics were different to freshwater artificial wetlands. Low densities, particularly shorebirds, were also expected at wetlands with imposed hydrological stability (Kings- ford et al., 2004). We tested whether waterbird composition differed among dif- ferent type of wetlands, and if species richness and densities were higher on natural (coastal lagoons) than artificial wetlands. 0006-3207/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.biocon.2009.08.007 * Corresponding author. Present address: ILWS – Institute of Land Water and Society, Charles Sturt University, P.O. BOX 789, Albury NSW 2640, Australia. Tel.: +61 02 60519914. E-mail addresses: mbellio@csu.edu.au (M.G. Bellio), richard.kingsford@unsw. edu.au (R.T. Kingsford), fogsl@slk.net (S.W. Kotagama). Biological Conservation 142 (2009) 3076–3085 Contents lists available at ScienceDirect Biological Conservation journal homepage: www.elsevier.com/locate/biocon