CLIMACT Starting Grant 2021: Progress and key discoveries two years later (Part 3)

Our project aimed at complementing the few existing data on Swiss urban soils with empirical soil measurements, to provide a more accurate estimation of the current urban soil organic carbon content ; explaining systemically the variations of urban Soil Organic Carbon as a function of several variables related to the practices and policies of soil management and urban development; and finally to considering the benefits of improvement measures and support decision making.

The main results of this research was undoubtably to demonstrate that urban soils do sequestrate a significant amount of carbon. The average urban Soil Organic Carbon is higher than the one of comparable regional soils under intensive agricultural uses. This crucial function is found even in some heavily anthropized soils.

Despite a notable disconnexon of top-soils from disturbed underlaying parent material, the comparison between Lausanne and Zurich have shown that preexisting geomorphological conditions are still driving Soil Organic Carbon: when there is more clay, there is more carbon sequestered.

Finally, important Soil Organic Carbon variations were found in all the studied vegetal covers, but comparison between privately and publicly maintained soils have shown that maintenance practices do have an impact on Soil Organic Carbon.

Those finding led to approach the definition of urban soils organic carbon sequestration potential, and the various possible strategies to preserve/improve it in a different and complementary way than previous research have approached crop soil management.

In the future, the challenge is to integrate (urban) soil organic carbon sequestration into a larger and more integrative approach to soil-based ecosystem services and related socio-environmental co-benefits.

The challenge is also to take such a functional approach to urban soils into account in urban planning and design project/policies.

These challenges are at the core of my research, teaching and dissemination activities as head of the new Chair for Transitioning Urban Ecosystems at the Technische Universität Berlin.

In the same way as the field of agronomy is able articulate fundamental knowledge in soils science to the daily practice of farmers, our approach to urban ecology, relating empirical measurement to urban planning and design, opened up concrete opportunities for carbon sequestration improvement in urban soils. In this view, urbanization (and more generally the human influence on soils) is not only considered in the negative terms of soil consumption and degradation but become part of the solution. Soil health is integrated to climate resilience of cities and people well-being.