Over the past 50 years, there have been major changes in human diets, including a global average increase in meat consumption and total calorie intake. We quantified how changes in annual per capita national average diets affected requirements for mined P between 1961 and 2007, starting with the per capita availability of a food crop or animal product and then determining the P needed to grow the product. The global per capita P footprint increased 38% over the 46 yr time period, but there was considerable variability among countries. Phosphorus footprints varied between 0.35 kg P capita-1 yr-1 (DPR Congo, 2007) and 7.64 kg P capita-1 yr-1 (Luxembourg, 2007). Temporal trends also differed among countries; for example, while China's P footprint increased almost 400% between 1961 and 2007, the footprints of other countries, such as Canada, decreased. Meat consumption was the most important factor affecting P footprints; it accounted for 72% of the global average P footprint. Our results show that dietary shifts are an important component of the human amplification of the global P cycle. These dietary trends present an important challenge for sustainable P management.

Cities are net consumers of food from local and global hinterlands. Urban foodshed analysis is a quantitative approach for examining links between urban consumers and rural agricultural production by mapping food flow networks or estimating the potential for local food self-sufficiency (LFS). However, at present, the lack of a coherent methodological framework and research agenda limits the potential to compare different cities and regions as well as to cumulate knowledge. We conduct a review of 42 peer-reviewed publications on foodsheds (identified from a subset of 829 publications) from 1979 to 2019 that quantify LFS, food supply, or food flows on the urban or regional scale. We define and characterize these studies into three main foodshed types: (1) agricultural capacity, which estimate LFS potential or local foodshed size required to meet food demands; (2) food flow, which trace food movements and embodied resources or emissions; and (3) hybrid, which combine both approaches and study dynamics between imports, exports, and LFS. LFS capacity studies are the most common type but the majority of cases we found in the literature were from cities or regions in the Global North with underrepresentation of rapidly urbanizing regions of the Global South. We use a synthetic framework with ten criteria to further classify foodshed studies, which illustrates the challenges of quantitatively comparing results across studies with different methodologies. Core research priorities from our review include the need to explore the interplay between LFS capacity and interregional food trade (both imports and exports) for foodsheds. Hybrid methodologies are particularly relevant to examining such dependency relationships in food systems by incorporating food flows into LFS capacity assessment. Foodshed analysis can inform policy related to multiple components of sustainable food systems, including navigating the social and environmental benefits and tradeoffs of sourcing food locally, regionally, and globally.

It is likely that half of the urban areas that will exist in 2050 have not yet been designed and built. This provides tremendous opportunities for enhancing urban sustainability, and using “nature in cities” is critical to more resilient solutions to urban challenges. Terms for “urban nature” include Green Infrastructure (GI), Green-Blue Infrastructure (GBI), Urban Green Space (UGS), and Nature-Based Solutions (NBS). These terms, and the concepts they represent, are incomplete because they tend to reduce the importance of non-terrestrial ecological features in cities. We argue that the concept of Urban Ecological Infrastructure (UEI), which came from a 2013 forum held in Beijing and from several subsequent 2017 publications, is a more inclusive alternative. In this paper we refine the 2013 definition of UEI and link the concept more directly to urban ecosystem services. In our refined definition, UEI comprises all parts of a city that support ecological structures and functions, as well as the ecosystem services provided by UEI that directly affect human outcomes and wellbeing. UEI often includes aspects of the built environment, and we discuss examples of this “hybrid infrastructure”. We distinguish terrestrial, aquatic, and wetland UEI because each type provides different ecosystem services. We present several examples of both “accidental” UEI and UEI that was explicitly designed and managed, with an emphasis on wetland UEI because these ecotonal ecosystems are uniquely both terrestrial and aquatic. We show how both accidental and planned UEI produces unexpected ecosystem services, which justifies recognizing and maintaining both purposeful and serendipitous types of UEI in cities. Finally, we posit that by incorporating both “ecological” and “infrastructure”, UEI also helps to bridge urban scientists and urban practitioners in a more transdisciplinary partnership to build more resilient and sustainable cities.