Evaluating the Impacts of a New Railway on Shorebirds: A Case Study in Central Portugal (Aveiro Lagoon)

Abstract

In 2007, the Portuguese Railway Company (REFER) began to build a new railway connecting the commercial port of Aveiro (Central Portugal) to the national rail network, which extended for about 9 km and crossed three of the remaining saltpans of the Aveiro Lagoon through a viaduct. Due to the importance of these habitats for shorebirds, and because the railway crossed a Natura 2000 site, the national biodiversity conservation authority required the impact assessment of this infrastructure. The study extended from 2006 (pre-construction), through 2008 and 2009 (construction), to 2011 (post-construction), encompassing four breeding and four wintering seasons. We used a Before-After-Control-Impact (BACI) design, with three impacted (those under the viaduct) and six control saltpans. During the breeding season (April–July) we monitored the numbers and breeding parameters of Black-winged stilt (Himantopus himantopus), and the numbers of Kentish plover (Charadrius alexandrinus) and Little tern (Sterna albifrons). In the winter, we monitored the numbers and spatial distribution of all shorebirds, and the activity of Dunlin (Calidris alpina). There was evidence for reductions in the abundance of the three breeding species in impacted saltpans in 2011, while no significant negative effects were found on abundances during 2008–2009 and on the breeding parameters of Black-winged Stilt. There was also evidence for reductions in wintering shorebird abundances in impacted saltpans in 2011, with no significant effects on abundances in 2008–2009, and on shorebird spatial distribution and activity patterns. Overall, the results suggest that the operation of a new railway close to important wetland habitats had negative impacts on the abundance of breeding and wintering shorebirds.