The new study provides the first global, population-level evidence quantifying how interacting threats drive biodiversity loss across animal populations. The findings have been published this week in Science Advances.
Researchers analysed population trends from 3,129 vertebrate populations worldwide between 1950 and 2020 and found that those exposed to combinations of threats such as climate change, disease, pollution and invasive species, are declining faster than those only affected by more widely recognised pressures such as habitat loss or exploitation.
"Conservation efforts have traditionally focused on the most widespread threats, such as habitat destruction or overexploitation," said co-lead author Dr Pol Capdevila, who carried out the research while at the University of Bristol but is now based at the University of Barcelona. "Our results show that other pressures, including disease, invasive species, pollution, and climate change, can lead to even faster population declines, especially when they occur together," he added.
While biodiversity loss has been extensively studied, much of the existing research has focused on species-level assessments or global summaries that do not capture how threats interact over time within individual populations.
The study combined data from WWF's Living Planet Database with Bayesian statistical models to analyse population trends across time, geography, and taxonomic groups. The modelling framework allowed the team to estimate how populations might have changed if threats had been removed individually or as a group.
To explore solutions, researchers used advanced statistical models to simulate 'what-if' scenarios, estimating how vertebrate populations might respond if threats were reduced or removed.
Co-lead author Dr Duncan O'Brien, Senior Research Associate in Bristol's School of Biological Sciences, added: "Our findings make it clear that conservation action must be coordinated across multiple pressures. Tackling threats one at a time will not be enough to halt ongoing biodiversity loss."
Their analysis showed that mitigating multiple threats together is essential to achieving stable or recovering vertebrate populations, and that single-threat interventions are unlikely to reverse global decline trends. However, if only one threat can be prioritised, then reducing overexploitation, habitat loss, or climate change impacts would likely deliver the greatest global benefits.
The findings have important implications for governments, conservation organisations, and international biodiversity agreements. The research suggests that effective conservation strategies should combine actions such as habitat protection, climate mitigation, pollution reduction, and invasive species control, rather than focusing on individual threats in isolation.
Paper:
'Halting predicted vertebrate declines requires tackling multiple drivers of biodiversity loss' by P. Capdevila et al, in Science Advances
