CE02 - Terre vivante

Retro-observatories of animal biodiversity during the Anthropocene: how have global changes affected populations and communities? – REPAST

Submission summary

Pressures on ecosystems have reached such an unprecedented rate that many ecosystems have been irreversibly damaged and that many animal populations have declined since the 1950s. Although human pressures on ecosystems have been identified, the mechanisms of biodiversity decline (i.e. relative importance of each pressure in the decline, temporality of events…) are poorly known. One reason is the lack of long-term data on population monitoring to study the impact of human pressures from past to present on animal populations and communities. REPAST proposes to use a retrospective multidisciplinary approach to study the impact of environmental pressures on the decline of bats through the study of guano cores collected in bat roosts. In caves or buildings, bat droppings (guano) fall to the ground and accumulate chronologically until reaching substantial thickness over time, and constitute historical archives containing temporally situated information about bat populations, environmental context, and human pressures. REPAST will test the general hypothesis that one or several stressors (habitat and climate changes, exposure to pollutants) will be associated to temporal variations of biological responses (pathogen prevalence, shift in diet, genetic diversity, bat richness). On 10 cores already sampled in bat colonies located in Burgundy Franche-Comté region, a robust chronology based on proxies used for paleoecological studies (14C, 137Cs, 210Pb concentrations) will be performed. The feasibility study done within the last 2 years shows that the cores date back from at least the 1950s, one being much older. Temporal variations of some anthropogenic pressures will also be reconstructed. Pollens will be studied on the cores to reconstruct the foraging areas (habitat) characteristics. The concentrations of some pollutants (~20 metals, 17 persistent organic pollutants including DDT and PCBs, and neonicotinoids) will be measured along the cores. Climate changes will be studied using meteorological data from 76 stations active since the 1940s across the region. Guano cores will also provide biological descriptors of bat colonies, which will be related to human pressures indices. The richness and composition of bat colonies, their diet using a metabarcoding approach, their exposure to eukaryotic pathogens, and their genetic diversity (using guano and Museum specimens already collected) will be reconstructed over time. Finally, historical archives and current counts from NGOs working in bat conservation will allow reconstructing the pattern of demographic trends and extinction risk of bat species since the 1940s. As the various anthropogenic pressures may act directly or indirectly on the biological responses, the complex set of variables measured in REPAST will be analysed using the structural equation modelling (SEM) framework. SEM’s causal diagrams will be constructed, based on explicit causal assumptions/hypotheses related to the mechanisms supposed to be involved between one or several pressures to one or several biological responses. The nature and the pattern of associations (what stressor(s) is(are) linked to what response(s) and how (from long and continuous associations to sudden shifts)) will improve our understanding of the mechanism(s) of bat decline. NGOs and stakeholders of bat roosts will be fully involved in the project and have already took part in the sampling process and share their data (e.g. bat counts). Apart from the classical scientific exploitation of the results (international meetings and articles), the large public will also be informed and invited to participate (e.g. in indicating colonies with guano accumulation unknown from NGOs) through a specific website and conferences. REPAST will allow gaining insights in the understanding of the mechanisms underlying the decline and the temporality of bat decline (and resilience) and, as some of the stressors still occur, may allow to predict and prevent new declines.

Project coordination


The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.



Help of the ANR 282,236 euros
Beginning and duration of the scientific project: December 2019 - 42 Months

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