Parks and Sequestration

Remarking that an early morning lecture on soil science doesn’t always draw a crowd, the speakers for Capturing Carbon in Urban Soil were delighted to see a packed house at Arup on June 2 for their discussion of urban carbon sequestration. Moderated by clean energy advocate Chris Neidl, the panel featured microbial biologist Peter Groffman, soil scientist Sara Perl Egendorf, and sustainable horticulturist Eric T. Fleisher. Collectively, the group highlighted the benefits of carbon sequestration in terms of climate change and soil health, as well as provided pointers for cultivating conversation around this “underground” topic in NYC.

The Science on Soil

Under a microscope it becomes clear that healthy soil is not dead, but rather teeming with life. Bacteria, fungi, algae, protozoa and other microorganisms are hard at work decomposing organic matter, fixing nitrogen, detoxifying chemicals and stimulating plant growth. Groffman explained that healthy soils need these microbial processes along with the carbon they beget. In fact, more carbon resides in soil than in the atmosphere and in all plant life combined—and there is room for more! When organic matter is removed from the soil—through erosion, tilling, harvesting, and decomposition—that stored carbon is released into the atmosphere. Therefore, by limiting unnecessary human disturbance, we can keep carbon in the ground where it is needed.

Forget Pawnee, We’ve Got Soil in NYC

Even though NYC may seem like a concrete jungle, Egendorf shared that 30 percent of its surface has soil cover—so there is a real possibility for sequestration. Furthermore, recent findings have shown that there can be a significant carbon stock even below the topsoil. The carbon-carrying capacity of soil depends on a variety of factors, such as compaction, erosion, decomposition, plant productivity and maintenance. This means carbon sequestration will vary depending on the type of soil and how the land is used. Through the work of soil scientists like Egendorf, researchers hope to better understand these variables in order to maximize carbon storage potential.

Treat Yo’ Soil: Correcting Soil Biology  

It’s tempting to look for a one-size-fits-all solution to soil management, but Fleisher emphasized that the complex ecology of a landscape requires an equally complex answer. Instead of searching for temporary or artificial fixes to soil and plant problems, the focus needs to shift to correcting the underlying biology—making dirt healthy and teeming with life as described by Groffman. Throughout his career, Fleisher has used organic landscaping to radically transform the health and resilience of public spaces. Focusing on the process rather than the product better equips green spaces to perform their function, be it sequestering carbon or serving as a public gathering space.

Changing the Conversation

When environmental conversation is dominated by talk of carbon as a villainous greenhouse gas, its function as the building block of life and an essential component of our soils is often overlooked. This discussion helped reframe the understanding of carbon and the life-giving role it plays beneath our feet. Furthermore, this event emphasized that it’s not just scientists who should be a part of this conversation: decision makers, landscape architects, urban gardeners and casual park users can all play a role in exploring the possibilities of carbon sequestration in NYC. When we allow and encourage soils to thrive, we keep carbon where it’s supposed to be—and where it’s helping, not harming.

About the authors

Rebecca Elzinga
Rebecca is the Technical Assistance Coordinator for Leadership & Group Development at City Parks Foundation. She previously interned at Urban Green.