Researchers measured biodiversity in five different metropolitan areas by calculating species diversity (birds or ferns) in neighborhoods, using the mean biological diversity of all neighborhoods as a baseline. They found that the majority of people in urban areas live with impoverished biodiversity. For example, of the 4.4 million people who lived in the four cities they investigated with bird data, 73.2% of them lived in areas that had biodiversity levels below the baseline. When the authors used only native species in their analyses, the percentages of people exposed to lower levels of biodiversity increased. In addition, when they used historical neighborhood biological diversity (rather than the mean neighborhood biological diversity) the percentages of people exposed to lower levels of biodiversity also increased (for example, in Tucson it went from 71.2% to 90.8%). The researchers conclude that many people experience biological uniformity (i.e., they tend to experience the same species, rather than a diverse mix) in their urban neighborhoods. They also discuss the implications this work has for human health, child development, and how we design our built environment.
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