Socioeconomics drive urban plant diversity

Abstract

Spatial variation in plant diversity has been attributed to heterogeneity in resource availability for many ecosystems. However, urbanization has resulted in entire landscapes that are now occupied by plant communities wholly created by humans, in which diversity may reflect social, economic, and cultural influences in addition to those recognized by traditional ecological theory. Here we use data from a probability-based survey to explore the variation in plant diversity across a large metropolitan area using spatial statistical analyses that incorporate biotic, abiotic, and human variables. Our prediction for the city was that land use, along with distance from urban center, would replace the dominantly geomorphic controls on spatial variation in plant diversity in the surrounding undeveloped Sonoran desert. However, in addition to elevation and current and former land use, family income and housing age best explained the observed variation in plant diversity across the city. We conclude that a functional relationship, which we term the "luxury effect," may link human resource abundance (wealth) and plant diversity in urban ecosystems. This connection may be influenced by education, institutional control, and culture, and merits further study.

Fig. 1.

Number of perennial plant genera per site across the Central Arizona–Phoenix long-term ecological research study area, superimposed on the major land-use categories. The study area encompasses the majority of Maricopa County, Arizona, but excludes Native American Indian reservation lands located in the east and to the south of the area shown.

Fig. 2.

Variation in the number of perennial plant genera with median family income (in dollars per year) from the U.S. Census of Population and Housing for the block group surrounding each survey site, at the urban sites. The regression line shown is an indicator of the linear relationship in the absence of the other predictor variables.