Comprehensive environmental impact assessment of transitioning from conventional to regenerative agriculture systems

Introduction

Picture a landscape where every farm rebuilds more than it extracts-where carbon flows into soil rather than the atmosphere, where biodiversity increases rather than declines, and where yields grow because of ecological health rather than despite ecological damage. This is the promise of regenerative agriculture, a set of practices defined not by specific techniques but by the outcome of improving ecosystem function over time [1] . Conventional agriculture has delivered impressive yield gains over the past half-century but at well-documented environmental costs: soil degradation, water pollution, biodiversity loss, and greenhouse gas emissions accounting for roughly 10-12% of global anthropogenic totals [2] . Regenerative practices-including cover cropping, reduced or no tillage, diversified rotations, integrated crop-livestock systems, and elimination of synthetic inputs-aim to reverse these trends [3] . However, comprehensive environmental assessments comparing the full impact profiles of conventional versus regenerative systems over meaningful timeframes remain scarce [4] . Most published comparisons either focus on a single environmental dimension (typically carbon) or cover only 2-3 years, missing the critical transition dynamics that determine longterm outcomes [5] . This research used life cycle assessment methodology to compare 12 matched pairs of conventional and regenerative farms in Castilla-La Mancha, Spain, across five environmental impact categories over a 10-year period, providing one of the most complete transition datasets available for Mediterranean dryland agriculture.

Environmental Assessment Framework

The assessment followed ISO 14040/14044 life cycle assessment standards with a functional unit of one hectare of arable land per year [6] . System boundaries included all on-farm operations, input manufacturing and transport, direct field emissions, and indirect emissions from land use change. Five impact categories were assessed: climate change (kg CO₂eq), eutrophication (kg N leached), ecotoxicity (kg active ingredient applied), soil loss (t erosion), and water depletion (m³ consumed). Carbon sequestration in soil was credited against emissions following IPCC Tier 2 methodology [7] . The 10-year timeframe was divided into early transition (years 1-3), mid-transition (years 4-6), and established phase (years 7-10).

Materials and Methods

Materials: Twenty-four farms in Castilla-La Mancha (38°50′-39°30′N, 2°30′-3°20′W) were grouped into 12 matched pairs based on soil type, climate zone, farm size, and initial management history. Within each pair, one farm transitioned to regenerative practices in 2012 while the other continued conventional management. Regenerative practices included: permanent cover crops (legume-grass mixtures), no-till or minimum tillage, diversified 4-5 year rotations, sheep grazing of crop residues and cover crops, and elimination of synthetic pesticides by year 3.

Methods

Farm-level data were collected annually through detailed inputoutput records, soil sampling (0-30 cm), yield monitoring, and biodiversity surveys. GHG emissions were calculated using IPCC emission factors for N₂O, CH₄, and CO₂ from fuel use and input manufacturing [8] . Nitrogen leaching was measured using ceramic suction cup lysimeters installed at 60 cm depth (three per farm). Soil erosion was estimated using the RUSLE model calibrated with local rainfall erosivity data [9] . Water use was tracked through irrigation records and rainfall data. Statistical comparison used paired t-tests and repeated-measures ANOVA in R (v.4.2). Regenerative systems showed significant reductions across all five impact categories (Table 1), with large effect sizes indicating substantial practical differences. GHG reductions of 62.8% reflected both lower input-related emissions (no synthetic fertilizer manufacturing) and soil carbon sequestration averaging 1.24 t C ha⁻¹ yr⁻¹. Erosion reduction of 73.6% resulted from permanent soil cover provided by cover crops and crop residues. The bar chart (Figure 1) shows regenerative agriculture achieving 27-74% lower environmental impact across all categories. Pesticide loading and soil erosion showed the greatest relative reductions.

Results

The bubble chart (Figure 2) reveals different recovery timelines for different services. Water infiltration responded fastest, showing 51% improvement by year 3. Biodiversity recovered steadily throughout. SOC accumulation was slowest, reaching 78% above baseline by year 10. Yield initially declined 12% but recovered by year 7 and exceeded conventional levels by year 10.

Discussion

The 62.8% GHG reduction is among the highest reported for temperate dryland comparisons, reflecting the combined effect of eliminating synthetic nitrogen (whose manufacture accounts for ~1.2% of global energy use), reducing diesel consumption through no-till, and sequestering carbon in soil [10] . The soil carbon sequestration rate of 1.24 t C ha⁻¹ yr⁻¹ is within the range of 0.5-2.0 t reported for Mediterranean systems adopting cover crops and no-till simultaneously [11] . The initial yield depression and subsequent recovery follow the widely reported "transition dip" pattern [12] . During years 1-3, soil biological communities are rebuilding, nutrient cycling has not yet reached equilibrium, and weed pressure may increase without herbicides. By year 7, enhanced soil biological function, improved water infiltration, and diversified rotations produced yields matching and then exceeding conventional systems. This transition period is the primary barrier to adoption, suggesting that targeted transition payments could accelerate uptake [13] .

Conclusion

Regenerative agriculture in Castilla-La Mancha delivered 61-74% reductions in GHG emissions, nitrogen leaching, pesticide loading, and soil erosion compared to conventional systems over a 10-year period. Yields recovered to conventional levels by year 7 and exceeded them by year 10. Soil organic carbon increased by 78% under regenerative management. The environmental benefits are clear and substantial, but the 3-5 year yield transition period represents a genuine economic barrier that policy instruments should address to enable widespread adoption.

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