Long term urban ecological change: Slow-rates, lags, and legacies

Background/Question/Methods: For 20 years, the Baltimore Ecosystem Study (BES) and Central Arizona-Phoenix (CAP) LTER programs have been conducting social-ecological research in urban ecosystems. We highlight both similarities and differences in findings from these two seemingly dissimilar cities. Strong legacies of past land use and social fabric drive contemporary land use-land cover change patterns in both Baltimore and Phoenix. We have also documented more recent trends in urbanization, development, and abandonment in both cities. We use various social survey techniques to document the perceptions, values, and choices that people make in our cities. From these, we know that social-ecological legacies and change at the parcel scale are important, including decisions people make about their front versus back yards. These two cities have quite different hydrologic infrastructure and legacies, both because of age (Baltimore is much older than Phoenix) and climate (Phoenix is arid; Baltimore is temperate mesic); these differences have broad social-ecological implications. Finally, our long-term research on urban faunal communities has shown interesting similarities in human-animal interactions in these two cities, with implications for the health and well-being of urban residents.

Results/Conclusions: In both cities, the dominant land-use legacy is the agriculture-to-urban transition. Former agricultural soils have higher carbon and nutrient content that urban soils with non-agricultural histories. Because of economic legacies, we find higher biodiversity in wealthier neighborhoods (termed the “luxury effect” by CAP and an “ecology of prestige” by BES). Both cities have seen reduced sprawl in recent decades, but only in Baltimore is this driven by policy (an urban-rural development boundary). Baltimore is characterized by abandonment of the urban core while in Phoenix abandonment, driven by massive foreclosures during the Great Recession, is widely distributed and heterogeneous. Both types of abandonment have parcel-scale ecological implications. In more stable parcels, we have found that residents of both cities make very different decisions about their back yards versus front yards. Beyond residential parcels, we have documented multi-decadal hydrologic changes in both cities. In Baltimore, degraded and broken stormwater and wastewater infrastructure has created major institutional challenges, some of which are being solved by new ecological infrastructure. In Phoenix, changes in stormwater infrastructure over the last 50 years have strongly influenced hydrologic and nutrient retention. Finally, neighborhood median income strongly controls bird community composition in both cities, and mosquito prevalence in Baltimore.