Global Assessment of Agricultural Productivity Losses from Soil Compaction and Water Erosion.

To guide us toward a sustainable future, the impacts of human activities on natural resources need to be understood and quantified. In this study on global agriculture, we use a Life Cycle Assessment framework to estimate potential long-term soil productivity losses caused by soil compaction and water erosion due to agricultural crop production. We combine several data sets to model spatially resolved Life Cycle Inventory information at the global level and multiply results with characterization factors from a previous publication. The global picture shows a compaction-stressed "Global North" and an erosion-stressed "Global South", with some countries and regions in between, for example, China and parts of South America. Results show that both compaction and water erosion impacts matter at the global level and that overall potential long-term productivity losses of 10-20% can be expected, with high relative impacts on low input production systems. These losses might limit long-term agricultural productivity and lead to additional land use change. Our work adds to and extends the discussion of global assessments of soil degradation. Furthermore, we prove the suggested framework to be applicable and useful for Life Cycle Assessments and other studies and provide results that can be used in such global assessments.

Assessing Impacts on the Natural Resource Soil in Life Cycle Assessment: Methods for Compaction and Water Erosion.

There are currently limited life cycle impact assessment methods existing for assessing impacts on the natural resource soil. In this paper, we develop methods for the assessment of compaction and water erosion impacts within one framework, which can be expanded with additional degradation processes in the future. Our methods assess potential long-term impacts from agricultural activities on the production capacity of soils and are able to distinguish between different management choices such as machinery selection and tillage practices. Characterization factors are provided as global raster data sets at high spatial resolution (∼1 km) and for larger geographic units including uncertainties of spatial aggregation. Uncertainties due to variability of climate and weather are provided where possible. The application of the methods is demonstrated and discussed in a simplified case study. Results show that in a highly mechanized scenario of global agriculture without any conservation measures, long-term yearly soil productivity losses due to compaction and water erosion can amount to up to double-digit percentages for major crops. This confirms the relevance of compaction and water erosion impacts for agricultural LCAs.

Defining freshwater as a natural resource: A framework linking water use to the area of protection natural resources.

PURPOSE: While many examples have shown unsustainable use of freshwater resources, existing LCIA methods for water use do not comprehensively address impacts to natural resources for future generations. This framework aims to (1) define freshwater resource as an item to protect within the Area of Protection (AoP) natural resources, (2) identify relevant impact pathways affecting freshwater resources, and (3) outline methodological choices for impact characterization model development. METHOD: Considering the current scope of the AoP natural resources, the complex nature of freshwater resources and its important dimensions to safeguard safe future supply, a definition of freshwater resource is proposed, including water quality aspects. In order to clearly define what is to be protected, the freshwater resource is put in perspective through the lens of the three main safeguard subjects defined by Dewulf et al. (2015). In addition, an extensive literature review identifies a wide range of possible impact pathways to freshwater resources, establishing the link between different inventory elementary flows (water consumption, emissions and land use) and their potential to cause long-term freshwater depletion or degradation. RESULTS AND DISCUSSION: Freshwater as a resource has a particular status in LCA resource assessment. First, it exists in the form of three types of resources: flow, fund, or stock. Then, in addition to being a resource for human economic activities (e.g. hydropower), it is above all a non-substitutable support for life that can be affected by both consumption (source function) and pollution (sink function). Therefore, both types of elementary flows (water consumption and emissions) should be linked to a damage indicator for freshwater as a resource. Land use is also identified as a potential stressor to freshwater resources by altering runoff, infiltration and erosion processes as well as evapotranspiration. It is suggested to use the concept of recovery period to operationalize this framework: when the recovery period lasts longer than a given period of time, impacts are considered to be irreversible and fall into the concern of freshwater resources protection (i.e. affecting future generations), while short-term impacts effect the AoP ecosystem quality and human health directly. It is shown that it is relevant to include this concept in the impact assessment stage in order to discriminate the long-term from the short-term impacts, as some dynamic fate models already do. CONCLUSION: This framework provides a solid basis for the consistent development of future LCIA methods for freshwater resources, thereby capturing the potential long-term impacts that could warn decision makers about potential safe water supply issues in the future.

Criticality of Water: Aligning Water and Mineral Resources Assessment.

The concept of criticality has been used to assess whether a resource may become a limiting factor to economic activities. It has been primarily applied to nonrenewable resources, in particular to metals. However, renewable resources such as water may also be overused and become a limiting factor. In this paper, we therefore developed a water criticality method that allows for a new, user-oriented assessment of water availability and accessibility. Comparability of criticality across resources is desirable, which is why the presented adaptation of the criticality approach to water is based on a metal criticality method, whose basic structure is maintained. With respect to the necessary adaptations to the water context, a transparent water criticality framework is proposed that may pave the way for future integrated criticality assessment of metals, water, and other resources. Water criticality scores were calculated for 159 countries subdivided into 512 geographic units for the year 2000. Results allow for a detailed analysis of criticality profiles, revealing locally specific characteristics of water criticality. This is useful for the screening of sites and their related water criticality, for indication of water related problems and possible mitigation options and water policies, and for future water scenario analysis.

Assessing the environmental impacts of soil compaction in Life Cycle Assessment.

Maintaining biotic capacity is of key importance with regard to global food and biomass provision. One reason for productivity loss is soil compaction. In this paper, we use a statistical empirical model to assess long-term yield losses through soil compaction in a regionalized manner, with global coverage and for different agricultural production systems. To facilitate the application of the model, we provide an extensive dataset including crop production data (with 81 crops and corresponding production systems), related machinery application, as well as regionalized soil texture and soil moisture data. Yield loss is modeled for different levels of soil depth (0-25cm, 25-40cm and >40cm depth). This is of particular relevance since compaction in topsoil is classified as reversible in the short term (approximately four years), while recovery of subsoil layers takes much longer. We derive characterization factors quantifying the future average annual yield loss as a fraction of the current yield for 100years and applicable in Life Cycle Assessment studies of agricultural production. The results show that crops requiring enhanced machinery inputs, such as potatoes, have a major influence on soil compaction and yield losses, while differences between mechanized production systems (organic and integrated production) are small. The spatial variations of soil moisture and clay content are reflected in the results showing global hotspot regions especially susceptible to soil compaction, e.g. the South of Brazil, the Caribbean Islands, Central Africa, and the Maharashtra district of India. The impacts of soil compaction can be substantial, with highest annual yield losses in the range of 0.5% (95% percentile) due to one year of potato production (cumulated over 100y this corresponds to a one-time loss of 50% of the present yield). These modeling results demonstrate the necessity for including soil compaction effects in Life Cycle Impact Assessment.