Challenges for incorporating long-term baselines into biodiversity restoration: A case study of the Dalmatian Pelican (Pelecanus crispus) in Britain

Species reintroductions are a core component of conservation but require critical assessment of past baselines. The Dalmatian Pelican Pelecanus crispus formerly occurred in Britain during the Holocene and there is interest in its possible reintroduction, but its regional extinction dynamics remain poorly understood. Pelican bones are known from subfossil and zooarchaeological contexts at 11 British Holocene sites in three regions (East Anglian Fens, Somerset Levels and Moors, Humber Valley). Dalmatian Pelican is positively identified from four of these sites, with other specimens only identified to genus level. Pelican populations were probably only present periodically in Britain during intervals of suitable climate and available habitat: there is little evidence for pelicans before the Bronze Age, and most sites are known or inferred to be Iron Age. There is a suggested Medieval specimen but no secure evidence of pelican presence after the Roman period. However, no specimens are directly dated, with age estimation reliant upon indirect dates or inference. Climatic niche modelling indicates that southern Britain was the northwestern limit of pelican climate tolerance under postglacial conditions, and pelicans may have been unable to persist regionally until the mid- or late Holocene. Considerable pelican breeding and foraging habitat might have existed until the Medieval period, but availability of suitable habitat fluctuated throughout the Holocene. Probabilistic analysis suggests possible mean extinction date estimates between ad 589 and ad 1587, highlighting uncertainty associated with indirect data, and hindering our ability to correlate pelican disappearance with putative extinction drivers (overexploitation, human modification of wetlands, or non-anthropogenic environmental changes). Improving our understanding of conditions associated with past pelican occurrence is essential for potential reintroduction decision-making, and direct dating of bones from all sites is needed to establish a secure chronological framework for correlating pelican presence and disappearance with regional landscape change. This review provides a robust framework for how to integrate past environmental baselines into conservation decision-making and reintroduction feasibility assessments.

Automated summary

Species reintroductions are an important part of conservation, but understanding the past baselines is crucial. This study examines the extinction dynamics of the Dalmatian Pelican in Britain and finds uncertain evidence of its presence and disappearance. The research provides a framework for integrating past environmental baselines into conservation decision-making and reintroduction feasibility assessments.