Inequity in consumption of goods and services adds to racial-ethnic disparities in air pollution exposure.

Fine particulate matter (PM2.5) air pollution exposure is the largest environmental health risk factor in the United States. Here, we link PM2.5 exposure to the human activities responsible for PM2.5 pollution. We use these results to explore "pollution inequity": the difference between the environmental health damage caused by a racial-ethnic group and the damage that group experiences. We show that, in the United States, PM2.5 exposure is disproportionately caused by consumption of goods and services mainly by the non-Hispanic white majority, but disproportionately inhaled by black and Hispanic minorities. On average, non-Hispanic whites experience a "pollution advantage": They experience ∼17% less air pollution exposure than is caused by their consumption. Blacks and Hispanics on average bear a "pollution burden" of 56% and 63% excess exposure, respectively, relative to the exposure caused by their consumption. The total disparity is caused as much by how much people consume as by how much pollution they breathe. Differences in the types of goods and services consumed by each group are less important. PM2.5 exposures declined ∼50% during 2002-2015 for all three racial-ethnic groups, but pollution inequity has remained high.

Five financial incentives to revive the Gulf of Mexico dead zone and Mississippi basin soils.

A central challenge in the Mississippi River Basin is how to continue to support profitable agricultural production, provide water supply, flood control, transportation, and other benefits, while reducing the current burden of environmental degradation. Several practices have been shown to reduce nutrient runoff and water pollution, and improve soil fertility, while often yielding profits for farmers. Yet many of these beneficial practices remain underutilized. Participants at an expert workshop identified five candidate financial mechanisms that could increase adoption of these beneficial farming practices in four focal Midwest states in the next five years: crop insurance premium subsidies, transformation of the private service provider business model, expansion and targeting of 2019 U.S. Farm Bill funding, development of new state funds, and direction of post-disaster federal funds towards habitat restoration, particularly in floodplains. This study provides rough approximations of the change in nutrient runoff and greenhouse gas (GHG) emissions, the annualized costs, and the nutrient and GHG reductions per dollar likely to result from deployment of each financial mechanism. Based upon these approximations, the adoption of these programs could reduce annual nitrate flows at the outlet of the Ohio and Upper Mississippi River Basins by 25%, surpassing the intermediate 2025 target (20% reduction) and achieving more than half of the long-term target (45% reduction) set by the Mississippi River/Gulf of Mexico Hypoxia Task Force. These approximations also illustrate that these five mechanisms could provide the same GHG reductions (∼43 Tg CO2e yr-1) as taking 12 coal-fired energy plants offline. The total cost of these five financial mechanisms is estimated at ∼$2.6 billion, or 64 g of nitrates and ∼17 kg of CO2e per dollar spent. These proposed solutions all face political, financial, cultural or institutional challenges, but with industry support, creative political action, and continued communication of both private and public benefits, they can create meaningful nutrient reductions and rebuild soils by 2022.

Socio-environmental consideration of phosphorus flows in the urban sanitation chain of contrasting cities.

Understanding how cities can transform organic waste into a valuable resource is critical to urban sustainability. The capture and recycling of phosphorus (P), and other essential nutrients, from human excreta is particularly important as an alternative organic fertilizer source for agriculture. However, the complex set of socio-environmental factors influencing urban human excreta management is not yet sufficiently integrated into sustainable P research. Here, we synthesize information about the pathways P can take through urban sanitation systems along with barriers and facilitators to P recycling across cities. We examine five case study cities by using a sanitation chains approach: Accra, Ghana; Buenos Aires, Argentina; Beijing, China; Baltimore, USA; and London, England. Our cross-city comparison shows that London and Baltimore recycle a larger percentage of P from human excreta back to agricultural lands than other cities, and that there is a large diversity in socio-environmental factors that affect the patterns of recycling observed across cities. Our research highlights conditions that may be "necessary but not sufficient" for P recycling, including access to capital resources. Path dependencies of large sanitation infrastructure investments in the Global North contrast with rapidly urbanizing cities in the Global South, which present opportunities for alternative sanitation development pathways. Understanding such city-specific social and environmental barriers to P recycling options could help address multiple interacting societal objectives related to sanitation and provide options for satisfying global agricultural nutrient demand.

Physical, technical, and economic accessibility of resources and reserves need to be distinguished by grade: Application to the case of phosphorus.

The amount of phosphorus in the total environment is finite, yet recent estimates suggest that more than enough phosphate ore resources exist in the lithosphere to meet future increases in demand during the next century. Still, it remains unclear how the accessibility of this resource stock - which is heterogeneous in terms of grade and location - will change as currently accessible resources are utilized, as extraction and processing technologies develop, and as the relative economic costs vary. This study uses an economic framework, the World Trade Model with Rectangular Choice-of-Technology, to link estimates of known geological resources of various grades with the technically and economically accessible reserves. Using the most recent public data on phosphate ore stocks and mining and technological capacity, this study estimates that the ~400,000teragrams (Tg) of known apatite ore (>1% P2O5 content) equate to ~110,000Tg when converted to potential reserves (~30% P2O5) using existing technologies, with over half of these remaining potential reserves converted from resources with grades below 20% P2O5. Corresponding global reserves are estimated at ~70,000Tg using the Rectangular Choice-of-Technology model, but since any reserve estimate is contingent on the state of the world economy, a set of five illustrative scenarios are constructed to show how this estimate can vary between ~67,000 and ~98,000Tg with only a small number of changes to the economic and technical parameters and variables. Calculating accessibility using consistent definitions for resources and reserves while distinguishing between grades not only creates a clearer picture of remaining non-renewable resources, but creates a framework that can be used to explore future geopolitical scenarios about ore availability, extraction technologies, supply networks, and global commodity prices.

Sustainable Sourcing of Global Agricultural Raw Materials: Assessing Gaps in Key Impact and Vulnerability Issues and Indicators.

Understanding how to source agricultural raw materials sustainably is challenging in today's globalized food system given the variety of issues to be considered and the multitude of suggested indicators for representing these issues. Furthermore, stakeholders in the global food system both impact these issues and are themselves vulnerable to these issues, an important duality that is often implied but not explicitly described. The attention given to these issues and conceptual frameworks varies greatly--depending largely on the stakeholder perspective--as does the set of indicators developed to measure them. To better structure these complex relationships and assess any gaps, we collate a comprehensive list of sustainability issues and a database of sustainability indicators to represent them. To assure a breadth of inclusion, the issues are pulled from the following three perspectives: major global sustainability assessments, sustainability communications from global food companies, and conceptual frameworks of sustainable livelihoods from academic publications. These terms are integrated across perspectives using a common vocabulary, classified by their relevance to impacts and vulnerabilities, and categorized into groups by economic, environmental, physical, human, social, and political characteristics. These issues are then associated with over 2,000 sustainability indicators gathered from existing sources. A gap analysis is then performed to determine if particular issues and issue groups are over or underrepresented. This process results in 44 "integrated" issues--24 impact issues and 36 vulnerability issues--that are composed of 318 "component" issues. The gap analysis shows that although every integrated issue is mentioned at least 40% of the time across perspectives, no issue is mentioned more than 70% of the time. A few issues infrequently mentioned across perspectives also have relatively few indicators available to fully represent them. Issues in the impact framework generally have fewer gaps than those in the vulnerability framework.

Feeding nine billion people sustainably: conserving land and water through shifting diets and changes in technologies.

In the early 21st century the extensive clearing of forestland, fresh water scarcity, and sharp rises in the price of food have become causes for concern. These concerns may be substantially exacerbated over the next few decades by the need to provide improved diets for a growing global population. This study applies an inter-regional input-output model of the world economy, the World Trade Model, for analysis of alternative scenarios about satisfying future food requirements by midcentury. The scenario analysis indicates that relying only on more extensive use of arable land and fresh water would require clearing forests and exacerbating regional water scarcities. However, a combination of less resource-intensive diets and improved agricultural productivity, the latter especially in Africa, could make it possible to use these resources sustainably while also constraining increases in food prices. Unlike the scenario outcomes from other kinds of economic models, our framework reveals the potential for a decisive shift of production and export of agricultural products away from developed countries toward Africa and Latin America. Although the assumed changes in diets and technologies may not be realizable without incentives, our results suggest that these regions exhibit comparative advantages in agricultural production due to their large remaining resource endowments and their potential for higher yields.