New Books in Science, Technology, and Society

Montserrat Bonvehi Rosich and Seth Denizen, "Thinking Through Soil: Wastewater Agriculture in the Mezquital Valley" (Harvard UP, 2025)

Dec 10, 2025

Dr. Seth Denison, a landscape architecture scholar, delves into the intriguing complexities of the Mezquital Valley, the world’s largest wastewater agricultural system. He discusses how soil records urban growth in Mexico City and contemplates its critical role in sustainability. Denison highlights the paradox of a recent protest against a treatment plant, emphasizing contaminant concerns. He also imagines a sustainable future by integrating Otomi practices and valuing ecosystem services, framing soil as pivotal to environmental solutions.

Ask episode

AI Snips

Chapters

Books

Transcript

Episode notes

INSIGHT

Soil As A Portrait Of Urbanization

The Mezquital Valley is the world's largest and longest-running wastewater agriculture system, forming soils from Mexico City's sewage over a century.
Its soils act as a chemical portrait of urbanization, revealing global supply chains and everyday contaminants from the city.

ANECDOTE

Farmers Protest A 'Clean' Treatment Plant

In November 2018 farmers protested and demanded closure of a new large wastewater treatment plant despite it being hailed as progress.
They claimed the plant was "stealing the shit"—removing organic matter they relied on for crop fertility.

INSIGHT

Fertility Versus Legacy Contaminants

The wastewater brings both fertility and persistent contaminants, creating a chemical trade-off that shapes soil sustainability.
Organic matter binds heavy metals, so reducing inputs can paradoxically release legacy metals into crops and water.

Get the Snipd Podcast app to discover more snips from this episode

Get the app

To think through soil is to engage with some of the most critical issues of our time. In addition to its agricultural role in feeding eight billion people, soil has become the primary agent of carbon storage in global climate models, and it is crucial for biodiversity, flood control, and freshwater resources. Perhaps no other material is asked to do so much for the human environment, and yet our basic conceptual model of what soil is and how it works remains surprisingly vague.

In cities, soil occupies a blurry category whose boundaries are both empirically uncertain and politically contested. Soil functions as a nexus for environmental processes through which the planet’s most fundamental material transformations occur, but conjuring what it actually is serves as a useful exercise in reframing environmental thought, design thinking, and city and regional planning toward a healthier, more ethical, and more sustainable future.

Through a sustained analysis of the world’s largest wastewater agricultural system, located in the Mexico City–Mezquital hydrological region, Thinking Through Soil: Wastewater Agriculture in the Mezquital Valley (Harvard UP, 2025) by Montserrat Bonvehi Rosich & Dr. Seth Denizen imagines what a better environmental future might look like in central Mexico. More broadly, this case study offers a new image of soil that captures its shifting identity, explains its profound importance to rural and urban life, and argues for its capacity to save our planet.

This interview was conducted by Dr. Miranda Melcher whose book focuses on post-conflict military integration, understanding treaty negotiation and implementation in civil war contexts, with qualitative analysis of the Angolan and Mozambican civil wars. You can find Miranda’s interviews on New Books with Miranda Melcher, wherever you get your podcasts.

Learn more about your ad choices. Visit megaphone.fm/adchoices

Support our show by becoming a premium member! https://newbooksnetwork.supportingcast.fm/science-technology-and-society