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A leading-edge guide to thinking about and planning for twenty-first-century cities in all their social, political, and ecological complexity The first "urban century" in history has arrived: a majority of the world's population now resides in cities and their surrounding suburbs. Urban expansion marches on, and the planning and design of future cities requires attention to such diverse issues as human migration, public health, economic restructuring, water supply, climate and sea-level change, and much more. This important book draws on two decades of pioneering social and ecological studies in Baltimore to propose a new way to think about cities and their social, political, and ecological complexity that will apply in many different parts of the world. Readers will gain fresh perspectives on how to study, build, and manage cities in innovative and sustainable ways

Context As urban areas increase in extent globally, domestic yards play an increasingly important role as potential contributors to ecosystem services and well-being. These benefits largely depend on the plant species richness and composition of yards. Objectives We aim to determine the factors that drive plant species richness and phylogenetic composition of cultivated and spontaneous flora in urban yards at the continental scale, and how these potential drivers interact. Methods We analyzed plant species richness and phylogenetic composition of cultivated and spontaneous flora of 117 private yards from six major metropolitan areas in the US. Yard plant species richness and phylogenetic composition were expressed as a function of biophysical and socioeconomic variables and yard characteristics using linear mixed-effects models and spatially explicit structural equation modeling. Results Extreme temperatures largely determined yard species richness and phylogenetic composition at the continental scale. Precipitation positively predicted spontaneous richness but negatively predicted cultivated richness. Only the phylogenetic composition of the spontaneous flora was associated with precipitation. The effect of lower temperatures and precipitation on all yard diversity parameters was partly mediated by yard area. Among various socioeconomic variables, only education level showed a significant effect on cultivated phylogenetic composition. Conclusions Our results support the hypothesis that irrigation compensates for precipitation in driving cultivated yard plant diversity at the continental scale. Socioeconomic variables among middle and upper class families have no apparent influence on yard diversity. These findings inform the adaptation of US urban vegetation in cities in the face of global change. ; National Science Foundation Macrosystems Biology Program in the Emerging Frontiers Division of the Biological Sciences Directorate; Long Term Ecological Research Program; "Yard Futures'' project from the NSF Macrosystems Program [EF-1638519]; "Ecological Homogenization of Urban America'' project - NSF Macrosystems Program [EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831, 121238320]; NSF Long Term Ecological Research ProgramNational Science Foundation (NSF) [DEB-0423476, BCS-1026865, DEB-0423704, DEB-9714833, OCE-1058747, 1238212, DEB-0620652, DBI-0620409] ; Research funding was provided by the National Science Foundation Macrosystems Biology Program in the Emerging Frontiers Division of the Biological Sciences Directorate and Long Term Ecological Research Program. The senior author was supported by the "Yard Futures'' project from the NSF Macrosystems Program (EF-1638519). Data collection was supported by the "Ecological Homogenization of Urban America'' project, funded by a series of collaborative grants from the NSF Macrosystems Program (EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831 and 121238320); and additionally by grants from the NSF Long Term Ecological Research Program supporting work in Baltimore (DEB-0423476), Phoenix (BCS-1026865, DEB-0423704 and DEB-9714833), Plum Island (Boston) (OCE-1058747 and 1238212), Cedar Creek (Minneapolis-St. Paul) (DEB-0620652) and Florida Coastal Everglades (Miami) (DBI-0620409). We are grateful to the botanical field teams involved in yard sampling and data organization: BAL-Charlie Davis, Dan Dillon, Erin Mellenthin, Charlie Nicholson, Hannah Saunders, Avery Uslaner; BOS-Emma Dixon, Roberta Lombardiy, Pamela Polloni, Jehane Semaha, Elisabeth Ward, Megan Wheeler; LA-Aprille Curtis, La'Shaye Ervin; MIA-Bianca Bonilla, Stephen Hodges, Lawrence Lopez, Gabriel Sone; MSP-Chris Buyarksi, Emily Loberg, Alison Slaats, Kelsey Thurow; PHX-Erin Barton, Miguel Morgan. ; Public domain authored by a U.S. government employee

In urban areas, anthropogenic drivers of ecosystem structure and function are thought to predominate over larger-scale biophysical drivers. Residential yards are influenced by individual homeowner preferences and actions, and these factors are hypothesized to converge yard structure across broad scales. We examined soil total C and total delta C-13, organic C and organic delta C-13, total N, and delta N-15 in residential yards and corresponding reference ecosystems in six cities across the United States that span major climates and ecological biomes (Baltimore, Maryland; Boston, Massachusetts; Los Angeles, California; Miami, Florida; Minneapolis-St. Paul, Minnesota; and Phoenix, Arizona). Across the cities, we found soil C and N concentrations and soil delta N-15 were less variable in residential yards compared to reference sites supporting the hypothesis that soil C, N, and delta N-15 converge across these cities. Increases in organic soil C, soil N, and soil delta N-15 across urban, suburban, and rural residential yards in several cities supported the hypothesis that soils responded similarly to altered resource inputs across cities, contributing to convergence of soil C and N in yards compared to natural systems. Soil C and N dynamics in residential yards showed evidence of increasing C and N inputs to urban soils or dampened decomposition rates over time that are influenced by climate and/or housing age across the cities. In the warmest cities (Los Angeles, Miami, Phoenix), greater organic soil C and higher soil delta C-13 in yards compared to reference sites reflected the greater proportion of C-4 plants in these yards. In the two warm arid cities (Los Angeles, Phoenix), total soil delta C-13 increased and organic soil delta C-13 decreased with increasing home age indicating greater inorganic C in the yards around newer homes. In general, soil organic C and delta C-13, soil N, and soil delta N-15 increased with increasing home age suggesting increased soil C and N cycling rates and associated C-12 and N-14 losses over time control yard soil C and N dynamics. This study provides evidence that conversion of native reference ecosystems to residential areas results in convergence of soil C and N at a continental scale. The mechanisms underlying these effects are complex and vary spatially and temporally. ; U.S. National Science FoundationNational Science Foundation (NSF) [EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831, 121238320] ; The authors thank La'Shaye Ervin, William Borrowman, Moumita Kundu, and Barbara Uhl for field and laboratory assistance. This research was funded by a series of collaborative grants from the U.S. National Science Foundation (EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831, 121238320). The authors appreciate valuable comments by anonymous reviewers on a previous version of the manuscript. ; Public domain authored by a U.S. government employee

Abstract
Residential landscapes are essential to the sustainability of large areas of the United States. However, spatial and temporal variation across multiple domains complicates developing policies to balance these systems' environmental, economic, and equity dimensions. We conducted multidisciplinary studies in the Baltimore, MD, USA, metropolitan area to identify locations (hotspots) or times (hot moments) with a disproportionate influence on nitrogen export, a widespread environmental concern. Results showed high variation in the inherent vulnerability/sensitivity of individual parcels to cause environmental damage and in the knowledge and practices of individual managers. To the extent that hotspots are the result of management choices by homeowners, there are straightforward approaches to improve outcomes, e.g. fertilizer restrictions and incentives to reduce fertilizer use. If, however, hotspots arise from the configuration and inherent characteristics of parcels and neighborhoods, efforts to improve outcomes may involve more intensive and complex interventions, such as conversion to alternative ecosystem types.