The world faces critical environmental challenges: soil degradation, biodiversity loss, and climate change. Agriculture significantly contributes to these issues, exceeding planetary boundaries related to biosphere integrity, biogeochemical flows, land-system change, freshwater use, and climate change. Simultaneously, agriculture is severely impacted by these challenges. Urgent changes are needed to ensure food security while mitigating climate change and restoring biodiversity on agricultural land. Increasing soil organic carbon is crucial for climate change mitigation, as it offers a substantial and technically feasible potential to stabilize the global climate system. Soils richer in carbon improve crop yields and resilience to climate variability. Phosphorus, essential for crop production, has finite rock resources, demanding improvements in phosphorus use efficiency. Higher soil organic matter enhances phosphorus availability. Biodiversity is vital for agricultural resilience against stressors like drought and disease outbreaks. Agroecology, with permaculture as a design framework, is proposed as a solution. Permaculture designs agriculturally productive ecosystems mimicking the diversity, stability, and resilience of natural ecosystems. It's a holistic approach emphasizing practices such as agroforestry, crop-livestock integration, and the promotion of semi-natural habitats, creating synergistic effects. While many individual permaculture practices have shown positive environmental impacts, there's a lack of scientific evidence on the overall effects of entire permaculture systems, especially in temperate regions. This study aims to address this gap by comprehensively evaluating a range of soil and biodiversity indicators on permaculture farms in Central Europe, comparing them to conventional agricultural practices.

The literature review highlights the urgency of addressing soil degradation, biodiversity loss, and climate change within the context of agriculture. Existing research demonstrates the positive effects of increased soil organic carbon for climate change mitigation and improved crop yields. The finite nature of phosphorus resources underscores the need for enhanced phosphorus use efficiency, which is often linked to higher soil organic matter content. Studies have shown the critical role of biodiversity in enhancing agricultural resilience and stability. Agroecological principles, particularly permaculture, are presented as promising approaches to sustainable agriculture. While various individual permaculture practices such as agroforestry, crop-livestock integration, and semi-natural habitat promotion show positive environmental benefits, there is a scarcity of research investigating the comprehensive impacts of fully integrated permaculture systems in temperate climates. The review emphasizes the need for studies that consider the holistic nature of permaculture, moving beyond isolated practices to assess the synergistic effects of integrated systems.

This study investigated nine permaculture farms (eight in Germany, one in Luxembourg) from 2019 to 2021. Each farm, or a designated portion, was managed according to permaculture principles, demonstrating economic self-sufficiency and integrating at least two land-use practices. At each location, one field of each permaculture land-use type and one paired control field with locally predominant agriculture were sampled. Soil samples were collected from two depths (0-10 cm and 10-30 cm). Soil organic carbon, various nutrients (total nitrogen, phosphorus, potassium, magnesium, boron, zinc, copper, and manganese), soil bulk density, and gravimetric/volumetric soil water content were analyzed. Earthworm abundance and species richness were assessed. Phospholipid fatty acids (PLFAs) were analyzed to evaluate microbial community structure. Vascular plant species richness was determined from 100 m² plots. Bird species richness was assessed using audio recorders deployed at each site. Farmers were interviewed to gather information on farm characteristics and permaculture practices. Data were compared to literature data from a European-wide study of conventional and organic farms and a comprehensive German soil inventory. Generalized linear mixed models were used to analyze the data, accounting for the paired sampling design and other factors such as soil texture class and pH. Post-hoc pairwise comparisons with Tukey correction were performed.

Permaculture sites showed significantly improved soil organic carbon (SOC) content (71% higher than controls and 94% higher than average German arable land) and SOC stocks (27% higher than controls and 37% higher than average German arable land). Carbon sequestration on permaculture sites was estimated at 0.82 ± 0.39 t ha⁻¹ yr⁻¹. Humic topsoil was 59% deeper on permaculture sites. Total nitrogen concentrations were 63% higher on permaculture sites. Concentrations of phosphorus, potassium, and magnesium were also significantly higher on permaculture sites. Boron and zinc concentrations were also increased. Soil bulk density in the deeper topsoil (10-30 cm) was 20% lower on permaculture sites. Earthworm abundance was 201% higher on permaculture sites compared to control fields and significantly higher than European organic and conventional farms. Total PLFA concentrations, bacterial PLFAs, and fungal PLFAs were significantly higher on permaculture sites. Vascular plant species richness was 457% higher on permaculture sites, exceeding that of European organic and conventional farms. Earthworm species richness showed a trend of 77% higher richness on permaculture sites. Bird species richness was 197% higher. The proportion of the surveyed area with trees was significantly higher on permaculture sites compared to European organic and conventional farms.

The findings strongly support the hypothesis that permaculture enhances soil carbon stocks, soil quality, and biodiversity. The significant increase in soil organic carbon on permaculture sites aligns with the importance of carbon sequestration for climate change mitigation. Improved soil quality, indicated by higher nutrient levels and lower bulk density, suggests enhanced crop production potential. The substantial increases in biodiversity across various taxa (plants, earthworms, birds) highlight permaculture's role in fostering ecosystem resilience and service provision. The observed improvements cannot be fully explained by the effects of individual practices alone, suggesting that the synergistic interactions between multiple integrated practices within the holistic permaculture system play a significant role. The deeper humic topsoil layer on permaculture sites suggests an even greater difference in carbon storage than measured in the top 30 cm. While the higher nitrogen levels on permaculture sites present a potential risk of gaseous losses, the minimal or no-till practices employed likely mitigate this risk. The increased biodiversity directly contributes to the enhanced ecosystem functioning and resilience of the permaculture systems.

This study demonstrates the significant positive impacts of permaculture on soil carbon stocks, soil quality, and biodiversity in Central Europe. These results highlight the potential of permaculture to contribute to the urgently needed transformation of agriculture towards environmental sustainability. The findings support permaculture as an effective tool for achieving sustainable development goals related to food security, sustainable production patterns, climate change mitigation, and land degradation and biodiversity loss. Future research should investigate the synergistic effects of integrated practices, nutrient and carbon pathways, and the crop yield potential of permaculture systems compared to conventional agriculture.

The relatively small number of permaculture sites included in this study and the high variance among them limit the generalizability of the findings. Further research on a larger scale across diverse climates is needed to confirm these findings. Long-term monitoring is necessary to assess the sustainability of these positive effects over time. The study focused on easily measurable biodiversity indicators and more detailed investigation of belowground biodiversity could provide more insight. While the study considered various factors such as soil texture and pH, other potential confounding factors might influence the results.