Shrinking Americans’ Daily Travel Footprint

Many U.S. cities have zoning policies that separate where people live from where they shop, work, and access daily services. This leads to limited access to amenities and long car trips for basic errands that ultimately result in higher transportation emissions, especially in low-density neighborhoods. Transportation is the largest source of U.S. greenhouse gas emissions, according to the U.S. Environmental Protection Agency, and the majority of these emissions come from passenger vehicles.

A study by YSE scientists published in Cities used generative AI to simulate how zoning reforms could reverse those patterns. The study, co-authored by Arianna Salazar-Miranda, assistant professor of urban planning and data science, analyzed data across 400 U.S. cities. Using a type of machine learning known as a generative adversarial network (GAN), the research team trained a model to learn the relationship between land-use patterns and the share of trips that can be completed within a 15-minute walk.

Once trained, the model allowed researchers to simulate hypothetical zoning reforms, essentially testing “what if” scenarios at a national scale. The scientists found that increasing land use mix by 20% leads to a 7% relative increase in short-distance trips.

“What we found is encouraging,” Salazar-Miranda says. “Cities with low baseline land use mix, lower density, and weaker street connectivity tend to see the largest gains when mixing increases. In those cities, even modest reforms can lead to sizable shifts toward shorter trips.”

Until this study, there was limited empirical evidence on how specific zoning reforms might affect travel behavior across different urban contexts. As cities across the U.S. revisit decades-old zoning codes amid climate, housing, and transportation challenges, the research offers a new way to understand where land-use reform may have the greatest impact and how targeted change could reshape daily mobility.

Trade-Offs of Biodegradable Plastics

Researchers from YSE found that switching to biodegradable plastics could slash toxic pollution by more than a third and dramatically reduce global waste by mid-century, but only if cities and companies invest in proper disposal systems. Without composting facilities, biodegradable plastics could double greenhouse gas emissions.

The study by Yuan Yao, the Manufacturer’s Association Professor of Industrial Ecology and Sustainable Systems, and Zhengyin Piao, postdoctoral associate, is the first to project the global environmental impact of biodegradable plastics across their lifecycle. It tracked materials from acquisition to disposal, including all end-of-life possibilities.

Published in Nature Reviews Clean Technology, the study found that substituting conventional plastic with biodegradable alternatives could reduce ecotoxicity by 34% and global waste by 65% by 2050 with ideal waste management.

“Biodegradable plastics can definitely help with plastic waste accumulation and ecotoxicity, but the benefits may not hold if their end of life isn’t managed properly,” Yao says.

Mapping the Future of Wildfires in a Warming World

A new review co-authored by Jennifer Marlon, senior research scientist, outlined how climate change is reshaping wildfire patterns worldwide.

The study, published in Science Advances, identified gaps in wildfire risk projections and the urgent need to understand the essential shifts in wildfire behavior in order to forecast future risks. Drawing on decades of fire research, satellite observations, climate model projections, and landscape fire modeling, the study’s authors found that traditional approaches fall short unless they integrate ecological, climatic, and human drivers.

In addition, most wildfire research is concentrated in North America, Australia, and Western Europe — yet most of the world’s burned area occurs in tropical savannas and grasslands, creating dangerous blind spots.

“Fire sits at the intersection of atmospheric science, ecology, public health, economics, land-use planning, and Indigenous knowledge systems,” Marlon says. “But these fields rarely work together in an integrated way. The science of projecting future fire needs to be as interdisciplinary as fire’s impacts are.”

Decoding the Everglades’ Climate Footprint

The Florida Everglades removes an average of 13.7 million metric tons of carbon dioxide from the atmosphere each year — but it also releases methane. A YSE-led study, published in the Proceedings of the National Academy of Sciences, analyzed these greenhouse gas fluxes across the wetland’s mangroves and freshwater marshes, providing a more detailed approach for guiding restoration efforts.

The researchers found that between 2003 and 2020, the Everglades increased carbon capture by 18%. Saltwater mangroves proved most effective, with methane offsetting only about 16% of their carbon uptake. Freshwater marshes fared worse, with methane canceling nearly 82% of their carbon gains.

“While different wetland types vary in how they capture and release greenhouse gases, the study confirms that the Everglades continues to function as a major carbon sink,” says Sparkle Malone, assistant professor of ecosystem carbon capture, and co-author of the study. “This diversity offers important insights for strengthening climate resilience and guiding restoration efforts.”