Understanding the Complexity: A Meta-Analysis of the Impact of Land Use Intensification on Soil Fauna in Global Agroecosystems

Increased land use intensity, especially the transition from extensive to intensively managed agroecosystems, is frequently referred to as one of the primary causes of the decline in global biodiversity and is thought to be the primary force influencing soil biodiversity. For appropriate land management in the face of future land use change, it is essential to comprehend how soil biodiversity responds to various land use regimes. Still, there is a great deal of uncertainty regarding the consistent responses of various taxonomic groups to intensification of land use.

We systematically assessed and quantified through meta-analysis the effects of various forms of land use intensification on soil organisms in global agroecosystems (192 studies included, 3190 pairwise observations comparing intensified land use to undisturbed ecosystems across 59 countries) and analyzed the dependence of these effects on abiotic factors such as soil properties (organic matter, pH, nutrient and water availability, texture) and climatic zone.

We observed a substantial decline in springtails abundance (-34%) and species richness (-16%), while earthworms experience a positive abundance trend (+217%) but a reduction in species richness (-12%). Enchytraeids exhibit a negative impact on abundance (-32%) with no effect on species richness. Mites show a positive increase in abundance (+129%), but a significant reduction in species richness (-50%). Nematodes, on the other hand, experience a negative impact on abundance (-7%) with no effect on species richness.

Focusing specifically on earthworms, we observed varying effects depending on the specific forms of intensification employed. Positive impacts on earthworm abundance are observed with agroforestry (+60%), cover crops, low input cropping (+113%), managed grasslands (+52%), vegetable gardens (+52%), and pastures (+218%). Conversely, negative effects are noted in arable cropland (-24%), orchards (-35%), specialty crops (-61%), crop livestock integration (-13%), and managed forests (-95%). Furthermore, the analysis reveals that the intensification effects on earthworm abundance vary across different climatic zones, with significant impacts observed in zones A and C. Higher intensification effects are noted in areas with greater mean annual precipitation, higher soil pH, finer soil textures (clayey, loamy, and silty), and increased organic matter content.

This comprehensive exploration sheds light on the intricate dynamics between land-use intensification and soil fauna, providing valuable insights for sustainable land management practices tailored to different ecological contexts.