Urban Underground: Agroecological Functions of Soils in the City

Introduction:

More people around the world now live in cities than in rural areas. While cities have long been economic and cultural centers, there is increasing demand for ecological and environmental services from urban spaces. Cities are meeting places where people connect, trade, eat, love, and live. Similarly, soils are at the nexus of earth’s terrestrial, atmospheric, and hydrologic cycles. Ecosystem services provided by soils buffer pressures from human development and climate change, which test the resiliency of natural habitats. Soils provide space for myriad organisms; capture, store, and cleanse water; and cycle nutrients, support plant production, and sequester carbon. Urban soils are highly disturbed by human activity and their ecosystem functions can be lost or compromised. Moreover, the concentrations of people, nutrients, and impervious space in cities heighten the importance of food production, nutrient cycling, and water retention from remaining urban soils. Urban agriculture, which utilizes local soils and nutrient rich organic amendments, is recognized for the ability to provide products, income, social benefits, and ecological services. Best management practices for anthropogenic soils (anthrosoils) and metrics to describe and evaluate their health are evolving.

Objectives:

The long-term goal of this project is to improve understanding of anthrosoils and their capacity for urban agriculture. The objective is to characterize soil development and nutrient and energy flows in agricultural soils in three different urban areas: 1) Medellín, Columbia; 2) Chicago, IL, USA; and 3) Seattle, WA, USA. While soil contaminants (e.g. heavy metals) are a concern in urban agriculture, the physical, hydrological, and biological issues with urban soils are equally important but less studied.

These three urban areas provide a diversity of cultural-industrial histories to evaluate anthropogenic influences. This study will compare farmed soils in urban and peri-urban environments to characterize soil formation, soil foodwebs and carbon dynamics, soil nutrients, and contaminants along a gradient of anthropogenic influence (less disturbed to highly disturbed).

Specific objectives include:
1) Describe soil pedogenesis in terms of horizonization, structure, and carbon depth profile.
2) Characterize soil foodweb complexity and energy flow.
3) Evaluate surface physical, chemical, and biological soil health metrics for utility in evaluating urban soils.
4) Suggest best management practices for urban agroecological soil management.