Human activity and related land use change are the primary cause of accelerated soil erosion, which has substantial implications for nutrient and carbon cycling, land productivity and in turn, worldwide socio-economic conditions. Here we present an unprecedentedly high resolution (250 × 250 m) global potential soil erosion model, using a combination of remote sensing, GIS modelling and census data. We challenge the previous annual soil erosion reference values as our estimate, of 35.9 Pg yr−1 of soil eroded in 2012, is at least two times lower. Moreover, we estimate the spatial and temporal effects of land use change between 2001 and 2012 and the potential offset of the global application of conservation practices. Our findings indicate a potential overall increase in global soil erosion driven by cropland expansion. The greatest increases are predicted to occur in Sub-Saharan Africa, South America and Southeast Asia. The least developed economies have been found to experience the highest estimates of soil erosion rates.

/pdf/an-assessment-of-the-global-impact-of-21st-century-land-use-rdg7ojdzqi.pdf

An assessment of the global impact of 21st century land use change on soil erosion.

Organic agriculture has a history of being contentious and is considered by some as an inefficient approach to food production. Yet organic foods and beverages are a rapidly growing market segment in the global food industry. Here, we examine the performance of organic farming in light of four key sustainability metrics: productivity, environmental impact, economic viability and social wellbeing. Organic farming systems produce lower yields compared with conventional agriculture. However, they are more profitable and environmentally friendly, and deliver equally or more nutritious foods that contain less (or no) pesticide residues, compared with conventional farming. Moreover, initial evidence indicates that organic agricultural systems deliver greater ecosystem services and social benefits. Although organic agriculture has an untapped role to play when it comes to the establishment of sustainable farming systems, no single approach will safely feed the planet. Rather, a blend of organic and other innovative farming systems is needed. Significant barriers exist to adopting these systems, however, and a diversity of policy instruments will be required to facilitate their development and implementation.

Organic agriculture in the twenty-first century.

Soil organisms are an integral component of ecosystems, but their activities receive little recognition in agricultural management strategies. Here we synthesize the potential of soil organisms to enhance ecosystem service delivery and demonstrate that soil biodiversity promotes multiple ecosystem functions simultaneously (i.e., ecosystem multifunctionality). We apply the concept of ecological intensification to soils and we develop strategies for targeted exploitation of soil biological traits. We compile promising approaches to enhance agricultural sustainability through the promotion of soil biodiversity and targeted management of soil community composition. We present soil ecological engineering as a concept to generate human land-use systems, which can serve immediate human needs while minimizing environmental impacts.

/pdf/an-underground-revolution-biodiversity-and-soil-ecological-2meyy3b4c1.pdf

An Underground Revolution: Biodiversity and Soil Ecological Engineering for Agricultural Sustainability

In their natural environment plants are part of a rich ecosystem including numerous and diverse microorganisms in the soil. It has been long recognized that some of these microbes, such as mycorrhizal fungi or nitrogen fixing symbiotic bacteria, play important roles in plant performance by improving mineral nutrition. However, the full range of microbes associated with plants and their potential to replace synthetic agricultural inputs has only recently started to be uncovered. In the last few years a great progress has been made in the knowledge on composition of rhizospheric microbiomes and their dynamics. There is clear evidence that plants shape microbiome structures, most probably by root exudates, and also that bacteria have developed various adaptations to thrive in the rhizospheric niche. The mechanisms of these interactions and the processes driving the alterations in microbiomes are however largely unknown. In this review we focus on the interaction of plants and root associated bacteria enhancing plant mineral nutrition, summarizing the current knowledge in several research fields that can converge to improve our understanding of the molecular mechanisms underpinning this phenomenon.

/pdf/the-role-of-soil-microorganisms-in-plant-mineral-nutrition-3jx2adg6hl.pdf

The Role of Soil Microorganisms in Plant Mineral Nutrition—Current Knowledge and Future Directions

Human appropriation of land for agriculture has greatly altered the terrestrial carbon balance, creating a large but uncertain carbon debt in soils. Estimating the size and spatial distribution of soil organic carbon (SOC) loss due to land use and land cover change has been difficult but is a critical step in understanding whether SOC sequestration can be an effective climate mitigation strategy. In this study, a machine learning-based model was fitted using a global compilation of SOC data and the History Database of the Global Environment (HYDE) land use data in combination with climatic, landform and lithology covariates. Model results compared favorably with a global compilation of paired plot studies. Projection of this model onto a world without agriculture indicated a global carbon debt due to agriculture of 133 Pg C for the top 2 m of soil, with the rate of loss increasing dramatically in the past 200 years. The HYDE classes “grazing” and “cropland” contributed nearly equally to the loss of SOC. There were higher percent SOC losses on cropland but since more than twice as much land is grazed, slightly higher total losses were found from grazing land. Important spatial patterns of SOC loss were found: Hotspots of SOC loss coincided with some major cropping regions as well as semiarid grazing regions, while other major agricultural zones showed small losses and even net gains in SOC. This analysis has demonstrated that there are identifiable regions which can be targeted for SOC restoration efforts.

https://www.pnas.org/content/pnas/114/36/9575.full.pdf

Soil carbon debt of 12,000 years of human land use

Human security has and will continue to rely on Earth's diverse soil resources. Yet we have now exploited the planet's most productive soils. Soil erosion greatly exceeds rates of production in many agricultural regions. Nitrogen produced by fossil fuel and geological reservoirs of other fertilizers are headed toward possible scarcity, increased cost, and/or geopolitical conflict. Climate change is accelerating the microbial release of greenhouse gases from soil organic matter and will likely play a large role in our near-term climate future. In this Review, we highlight challenges facing Earth's soil resources in the coming century. The direct and indirect response of soils to past and future human activities will play a major role in human prosperity and survival.

/pdf/soil-and-human-security-in-the-21st-century-3wppnsj44i.pdf

Soil and human security in the 21st century

Isotopic and geomorphic evidence for Holocene Climate, Southwestern Kansas

SUMMARY

Two mountain watersheds in eastern USA showed sensitivity of their bedrock type to acidification from changes in atmospheric input: they were a Catoctin Mountain watershed on Precambrian metabasalt, and a Massanutten Mountain watershed developed on Silurian metaquartzites and shales. The role of clay minerals to neutralize potential increases in acid deposition was examined. Landscape position and drainage characteristics influence the clay mineral suites present at Catoctin, and an expandable clay component enables this watershed to adequately buffer the hydrochemical systems. A 14 A hydroxy-interlayer vermiculite provided a sink for A13+, and also a possible neutralizing effect in the second watershed which was highly sensitive to acid deposition.

Clay‐mineral contribution to the weathering mechanisms in two contrasting watersheds

The soil science discipline has undergone significant changes since its establishment in the 1900s; from strong connections with agronomy to a broader focus on ecosystems, earth, and environmental sciences while also during this period experiencing a notable increase in diversity among soil scientists. In this review, we explore soil science from the perspective of gender demographics and disciplinary foci of soil scientists. We examine graduate student enrollment metrics; employment information in academia, the federal government, and the private sector; and membership data from SSSA to gain deeper insight into these changes and the implications for the future of soil science. Women earn nearly half of the advanced soil science degrees. The number of women pursuing soil science careers has also increased, albeit less markedly, as women now comprise 24, 26, and 20% of the soil scientists in academic faculty positions, federal agencies, and private industry, respectively. However, there is reason for concern that women linger in intermediate levels of employment, and further attrition occurs along the career ladder with only ∼18% of the highest employment levels held by women; even fewer reach executive leadership levels in any sector. The growing participation of women in soil science is further reflected in a nearly 45% increase in female membership and meeting attendance in SSSA over the past decade, but recognition of their accomplishments and their presence in SSSA leadership positions remains low. We provide recommendations toward greater inclusion and gender diversity as this represents an important pathway to grow and innovate our science.

Carolyn Olson

Papers

Soil and human security in the 21st century

Isotopic and geomorphic evidence for Holocene Climate, Southwestern Kansas

Clay‐mineral contribution to the weathering mechanisms in two contrasting watersheds

Women in Soil Science: Growing Participation, Emerging Gaps, and the Opportunities for Advancement in the USA

The Soil Record of Quaternary Climate Change