ANR AtlantAves

Summary of the project

Most of bird species extinctions and extirpations (local extinctions) in recent millenia took place on islands and were caused by waves of human colonizations and their impacts (hunting, deforestation, introductions of predators or competitors, or of diseases, pollution etc); but some were caused by natural causes (e.g., climate change, sea level changes, eruptions). However, very little is known on the specific effects of past climatic vs anthropic impacts on recent biodiversity declines (global and local, in the past millenia), while deciphering these two effects would be of major importance to adapt conservation strategies since it would render possible to shed light on what can be expected if the current anthropogenic impact on climate is maintained as is or increases, plus continuing “classical” human impacts. Considering that recent avian extinctions affected principally oceanic islands, and that some volcanic islands show a fossil record dominated by fossil birds and spanning pre- and post-human arrival, a study focusing of such islands would be highly relevant to decipher climatic and anthropogenic impacts through time.

We therefore propose an extensive and integrated study of the fossil records of two South Atlantic volcanic islands : Saint Helena and Ascension islands, both showing a diversity of subfossil localities spanning human arrival, but also earlier climate changes including the Pleistocene-Holocene transition, and known to be highly prolific in fossil material, yet under-investigated until recently. After a first successful fieldwork on Saint Helena in August-September 2022 yielding 7000 fossils, we will continue unearthing and identifying fossil material, with urgency for further prospecting because the alluvial outcrops containing fossils on these two islands are continuously being eroded or washed into the sea. This newly-collected subfossil material, consisting in (i) bird material (bones, eggshells, feathers) and (ii) other elements of these native ecosystems (pollen, wood, gastropods etc.) since the late Pleistocene, will be studied together with material already available such as naturalised specimens and extant bird genetic data. Importantly, datings will be realized to better position localities through time. Occurrences of bird species through time will be completed and precisely established. Among other analyses, biogeochemistry of calcium isotopes into bones will reveal evolution of trophic levels in selected seabirds; paleogenomics on subfossil and historical specimens will yield insights into links between genetic diversity and vulnerability in island birds. All these results will be confronted with known climatic evolution (since the Pleistocene), and also with anthropic impacts through time (since 1501 AD).

Our interdisciplinary approach will allow testing for how anthropic and climatic impacts differentially affected birds on these islands, according to their ecomorphology, or their phylogenetic position, either by affecting their trophic position, their genetic diversity, or more profoundly their presence and survival (leading to extirpation or extinction for some species). In turn, results will highlight vulnerabilities of different groups of birds and thus this knowledge will be beneficial as a guide for fine insular biodiversity conservation according to species, and set priorities in reintroductions and ecosystems restoration. In addition, outreach will promote the diffusion of all this crucial information for the conservation of the natural heritage of these islands, and the participation of local people to all steps of the project will strengthen their future implication in the knowledge of the past, future conservation, and restoration, all this being met with enthusiasm by our partners on St Helena and Ascension.

List of LGL-TPE participants:

• Anaïs Duhamel
• Antoine Louchart
• Jeremy Martin
• Nicolas Rinder
• Emmanuel Robert
• Philippe Sorrel