Systematic Review Protocol: What causes biodiversity loss? A systematic review of counterfactual evidence on human impacts

Le résumé fourni par la source

Addressing the root causes of the biodiversity crisis – accelerated declines in the variety of life on Earth – is at the forefront of environmental policy and research. Although the five main direct drivers of biodiversity loss (land/sea-use, resource-extraction, climate change, pollution, and invasive species) have been identified and quantified, indirect drivers (i.e., broadly described as demographic, sociocultural and economic, technological, and governance factors) remain under-specified. Effectively mitigating the biodiversity crisis therefore requires a clearer understanding of the specific human actions and decisions through which indirect drivers translate into direct pressures and, ultimately, biodiversity impacts. Improving such understanding requires integrating three elements. First, beyond broad categories of indirect/direct drivers, there is a need to identify and quantify specific anthropogenic mechanisms – defined here as concrete factors whose variation helps explain the causal process linking indirect and direct drivers. Second, causally-rigorous methods are needed to establish credible and quantifiable causal chains linking indirect drivers to direct drivers and biodiversity outcomes. Third, biodiversity-explicit metrics are needed (rather than commonly used land-use or vegetation cover proxies), and are increasingly available due to recent data and technological advances. Existing literature reviews have tended to address these elements in isolation. Reviews quantifying biodiversity impacts largely overlook the underlying causal mechanisms, while reviews assessing causally-rigorous evidence frequently focus on conservation interventions and rely on biodiversity proxies. As a result, a synthesis that combines biodiversity-specific metrics, causally rigorous methods, and explicit anthropogenic mechanisms is currently lacking. Here, we outline the protocol for a systematic review that addresses this gap – aiming to answer what causally rigorous evidence exists on the anthropogenic mechanisms driving biodiversity impacts?. More specifically, we ask: 1) what specific anthropogenic mechanisms are identified in the evidence, 2) what are the ex-post causally-rigorous designs being used, and 3) what biodiversity-specific outcome metrics underpin this evidence, and 4) what thematic and geographic patterns and gaps characterize the evidence base. Our review will include peer-reviewed studies using biodiversity-specific outcomes, counterfactual-based experimental or quasi-experimental designs, and explicit evaluation of anthropogenic mechanisms. Evidence will be systematically extracted, mapped, and critically appraised for methodological rigor and risk of bias. Identified gaps will help guide future research priorities for understanding and mitigating biodiversity loss.

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