Introduction

This study assesses the global impact of human pressures on biodiversity by synthesising evidence across ecosystems, organism groups and spatial scales. Despite extensive prior research, uncertainty has persisted around whether human activities drive consistent biodiversity loss, local change or biotic homogenisation. The authors address this gap through a large-scale, impact–reference meta-analysis.

Human Pressures And Biodiversity Change

The analysis covers five dominant anthropogenic pressures: habitat change, resource exploitation, pollution, climate change and invasive species. Data were compiled from 2,133 publications, encompassing 97,783 sites and 3,667 independent comparisons across terrestrial, freshwater and marine systems. These pressures are shown to consistently alter biodiversity, but with effects that differ in magnitude and direction depending on context.

Community Homogenisation Across Space

Contrary to long-standing expectations, the study finds no clear global trend towards biotic homogenisation. The average effect of human pressure on community homogeneity is slightly negative, indicating biotic differentiation rather than convergence. However, spatial scale strongly mediates outcomes: communities tend to homogenise at continental or global scales, while differentiation dominates at local and plot scales. Resource exploitation and pollution are associated with particularly strong local differentiation effects.

Shifts In Community Composition

Across all pressures and ecosystems, human activities cause pronounced shifts in species composition. The mean log-response ratio for compositional change is strongly positive, indicating that impacted communities consistently differ from reference communities. All five pressure types significantly affect composition, with pollution and habitat change exerting the largest effects. Microbes and fungi show the strongest compositional shifts, while mammals and fish exhibit weaker responses. These results demonstrate that biodiversity change is not limited to species loss but involves systematic reassembly of communities.

Changes In Local Diversity

Local species richness declines under human pressure. Based on 1,139 comparisons, impacted sites exhibit an average reduction in local diversity relative to reference sites. Pollution and habitat change are again identified as the strongest drivers. In contrast to compositional shifts, larger-bodied organisms, including vertebrates, experience the greatest local diversity losses, aligning with documented population declines and extinction risk. The findings challenge claims of stable local biodiversity by using direct impact–reference comparisons rather than time-series alone.

Linkages Between Biodiversity Dimensions

The study demonstrates a clear relationship between local diversity loss, compositional change and community differentiation. Greater declines in local diversity are associated with stronger shifts in composition and increased differentiation across space. This pattern is consistent across biomes, pressures, organism groups and spatial scales, supporting theoretical predictions that different biodiversity dimensions are interdependent. While causality cannot be inferred, the associations reinforce the cumulative impacts of human pressures.

Methods Overview

The authors employ a meta-analytical framework based on distance-based ordination plots, extracting community-level data from PCoA and NMDS analyses. Effect sizes are calculated as log-response ratios comparing impacted and reference communities for homogeneity, compositional shift and local diversity. Mixed-effects models test the influence of biome, pressure type, organism group and spatial scale. Robustness checks indicate limited publication bias and consistent results across observational and experimental studies.

Implications For Conservation And Policy

The findings provide a quantitative benchmark for assessing biodiversity change under human pressure. They highlight that biodiversity responses are context-specific rather than uniform, underscoring the need for conservation strategies that account for pressure type, scale and organismal differences. Addressing biodiversity loss requires tackling all major human pressures simultaneously, rather than prioritising a single driver. The study offers a global evidence base to inform monitoring and mitigation strategies.