SPRING 2025 | 13 At Duke, he inherited a long-term soil experiment that examines how a pine forest has restored soil after 150 years of cotton farming. In his book “Understanding Soil Change,” Richter has shown how soil carbon, nitrogen, phosphorus and a dozen other chemical elements change in soil over time, affecting soil far more deeply than previously understood. Like Knoll, Richter has often used isotopes to estimate how the Earth cycles its chemical elements. Starting in 2005, he began examining other long-term soil experiments (LTSEs) around the world, compiling them into a database of more than 200 studies. Along with colleagues, he has shown how the explosion in agricultural production brought on by improvements in fertilizer and other practices has had unintended consequences in soil erosion, runoff and overfertilization, affecting the environment and public health. More recently, he’s begun looking at city soils, using new instruments that can detect potential contaminants within seconds. After the catastrophic wildfires in Los Angeles in January, he has analyzed more than 300 soil samples provided by citizens, showing potentially dangerous amounts of lead and other contaminant metals. Richter has become so passionate about tracing humankind’s impact on the Earth that he joined the Anthropocene Working Group, a collection of geological scientists who, after 10 years of study, proposed to rename our current geological epoch from the Holocene to the Anthropocene given the scale at which humans are changing the land, ocean and atmosphere. While the scientific community has been resistant to the proposal so far, he is optimistic that it will gain traction over time and help bring new attention to the Earth sciences to better learn how we are changing our planet for better or worse. “Prior to this, geologists have always looked back through time, but we are trying to come to grips with the human role in the present,” Richter says. “This question is as much geological as it is philosophical.” L “WHAT WE SEE AT THE END OF THE PERMIAN PERIOD IS REALLY A DISTANT MIRROR ON THE 21ST CENTURY.” —Andrew Knoll ’73 Daniel Richter ’73, Theodore S. Coile Distinguished Professor in the Nicholas School of the Environment at Duke University, examines soil with graduate students. JARED LAZARUS
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