The critical role of fossil carbon dioxide emissions in driving global warming is well established. However, until now, urban centers have faced significant challenges in accurately quantifying local emissions and discerning whether mitigation strategies are effectively curbing carbon output. UC Irvine’s earth system scientists, spearheaded by Claudia Czimczik, recognized that plants integrate atmospheric CO2 during photosynthesis, leaving a distinct radiocarbon fingerprint that can be analytically disentangled to distinguish fossil-derived carbon from biogenic sources. This insight underpins their pioneering methodology.

The research team conducted extensive sampling of managed turfgrasses throughout urban and rural areas of Southern California. Turfgrass, unlike wild or invasive species, offers a reliable proxy due to its regular maintenance and growth cycles, providing a consistent temporal window reflecting atmospheric conditions over a short but meaningful interval. By harvesting the uppermost layers of frequently mowed grass—typically cut every one to two weeks—the scientists ensured each sample captured approximately a fortnight of carbon assimilation, tightly aligning biological and atmospheric measurements.

Simultaneously, high-precision greenhouse gas monitoring instruments, provided through collaboration with Manvendra Dubey of Los Alamos National Laboratory, were deployed to obtain concurrent atmospheric CO2 concentration data. This integrative approach allowed the team to correlate radiocarbon signals extracted from the plant tissue with contemporaneous airborne CO2 metrics, thereby refining the spatial resolution and accuracy of emission maps.

The results revealed well-defined “carbon dioxide domes” over Los Angeles, a phenomenon rooted in the region’s unique topography where surrounding mountain ranges confine pollutants within the basin. This effect creates localized atmospheric pockets with elevated fossil fuel CO2 concentrations. Critically, the new turfgrass radiocarbon mapping method effectively captured these complex spatial patterns, suggesting strong applicability for evaluating emission control policies.

Importantly, this methodology addresses previous gaps in urban carbon monitoring infrastructure, providing a cost-effective yet precise tool adaptable for cities with limited resources. By harnessing vegetation as an intrinsic environmental archive, municipalities gain access to a scalable system capable of delivering fine-grained data necessary to track decarbonization efficacy across diverse neighborhoods and jurisdictions.

Extending beyond prior studies executed during the COVID-19 pandemic—which relied on invasive grass samples collected by citizen scientists and demonstrated stark emission fluctuations during lockdown and reopening phases—this work represents a methodological evolution. Shifting focus to managed turfgrasses enables year-round surveillance, eliminating seasonal sampling bias and enhancing temporal continuity. Additionally, the integration of atmospheric measurement experts has elevated analytical rigor, ensuring robust interpretation of complex radiocarbon dynamics.

Despite the promising outcomes, researchers caution that the interplay of local meteorology and urban form influences fossil carbon distribution. Los Angeles’s basin-mountain setting, which traps emissions, affords a relatively stable scenario for detecting fossil CO2. In contrast, cities subject to strong and consistent wind transport may present challenges for signal retention in vegetation and require calibration of the approach to account for increased atmospheric mixing.

Looking forward, the research team envisions broad implementation of their radiocarbon turfgrass technique as an indispensable component of urban climate strategy toolkits. By furnishing high-resolution emission maps with temporal sensitivity, local governments can precisely evaluate the impact of specific policies such as transportation electrification, building efficiency upgrades, and industrial emission reductions. This capacity will empower data-driven decision-making to accelerate progress toward carbon neutrality.

This innovative scientific effort underscores the transformative potential of interdisciplinary collaboration across earth system science, atmospheric chemistry, and urban ecology. With support from the U.S. National Science Foundation and in cooperation with partners from UC Riverside and the University of Utah, the UC Irvine team exemplifies how environmental measurement innovations can translate into actionable insights for climate mitigation.

To summarize, UC Irvine’s research charts a compelling new frontier in urban greenhouse gas monitoring by deploying radiocarbon analysis of managed turfgrass as an accurate, practical, and scalable surrogate for fossil fuel CO2 emissions. This breakthrough promises to enhance transparency, accountability, and efficacy in municipal climate initiatives, fueling momentum for meaningful emission reductions in American cities and beyond.

Subject of Research: Not applicable

Article Title: Not provided

News Publication Date: November 3, 2025

Web References:
https://doi.org/10.1029/2025JD043336

References:
The study published in the Journal of Geophysical Research: Atmospheres, October 27, 2025.

Image Credits: Not provided

Keywords:
Earth systems science, Greenhouse gases

Utilizing state-of-the-art satellite radar interferometry, the research team constructed detailed, high-resolution maps capturing the subtle yet consequential subsidence patterns beneath densely populated metropolitan areas. These cities together house approximately 34 million residents—roughly 12% of the entire U.S. population—highlighting the extensive societal reach of this geophysical process. Satellite-based monitoring offers unprecedented precision, measuring tiny ground motions that, over time, can compromise foundational stability in complex urban environments.

The study’s results are unequivocal: every city examined exhibits significant land sinking, with at least 20% of urban areas subsiding. Even more alarming, 25 out of the 28 cities studied display subsidence in over 65% of their urban footprint. This widespread phenomenon accentuates a creeping threat that has received too little attention amid other urban challenges like traffic congestion or air pollution but poses a silent and persistent risk to critical infrastructure assets.

Subsidence, the gradual downward settling or sudden sinking of the ground surface, can severely degrade the structural integrity of buildings, transportation networks, bridges, and dams. Leonard Ohenhen, a former Virginia Tech graduate student and lead author of the study, emphasizes that even seemingly minor vertical shifts accumulate over time. These incremental movements may initially go unnoticed but progressively magnify vulnerabilities within urban systems, exacerbating weak points and significantly elevating flood risks in low-lying and coastal areas.

In terms of magnitude, cities including New York, Chicago, Seattle, and Denver sank at rates near 2 millimeters per year. Texas cities, however, present a starkly different and more troubling picture. Multiple Texan urban centers registered elevated subsidence rates — 5 millimeters annually on average — with localized pockets in Houston experiencing accelerations up to 10 millimeters per year. This demonstrates dramatic heterogeneity in subsidence velocity, highlighting the importance of localized monitoring and targeted intervention measures.

Houston’s experience elucidates one of subsidence’s most insidious aspects: spatial variability. Within metropolitan regions, specific zones may sink markedly faster than adjacent neighborhoods, inducing uneven ground deformation. Unlike flooding, which typically poses a risk when water levels breach certain heights, differential land motion incrementally imposes mechanical stresses on infrastructures. Uneven sinking can induce cracking, tilting, and foundational destabilization, often long before damage becomes perceptible, undermining safety in a stealthy and persistent manner.

Manoochehr Shirzaei, Associate Professor at Virginia Tech and co-investigator on the project, explains that rising variability in subsidence rates significantly amplifies infrastructure risk. Cities like New York, Las Vegas, and Washington, D.C., display such differential sinking patterns, raising red flags for urban planners and engineers tasked with maintaining resilient frameworks in dynamic environments. The latent nature of these risks means that irreversible damage may manifest suddenly and catastrophically after years of undetected degradation.

The root cause of this alarming subsidence is primarily anthropogenic: groundwater extraction. As urban populations burgeon and the demand for potable freshwater soars, cities increasingly tap into underground aquifers to meet their needs. When water is withdrawn from these subterranean reservoirs faster than natural replenishment occurs, the aquifer materials compact, causing the overlying land surface to subside. This geotechnical process involves soil consolidation and loss of pore water pressure, physically compressing sediment layers and shrinking the volume of the subsurface matrix.

Compounding this issue is climate variability and shifting precipitation patterns, which interact with socio-economic growth to accelerate subsidence trends. Fluctuations in seasonal rainfall and prolonged drought conditions reduce recharge rates of aquifers, intensifying depletion linked to human extraction. As previously stable urban areas begin to subside, they become increasingly vulnerable to flooding, infrastructure failure, and progressive land degradation, further complicating urban sustainability and disaster risk management efforts.

Given the widespread risks highlighted in the study, integrating continuous land subsidence monitoring into urban planning frameworks is imperative. This involves establishing systematic, long-term geodetic observation networks capable of detecting minute land surface movements in real time, enabling early warning and preemptive response. Moreover, detailed mapping of differential subsidence can inform engineering design adjustments and prioritize areas for infrastructure reinforcement to ensure resilience against uneven ground movement.

Mitigation strategies proposed by the research emphasize sustainable groundwater management practices aimed at reducing excessive withdrawals. Efforts may include promoting alternative water sources, enhancing aquifer recharge programs, and implementing regulatory frameworks that control usage rates. Equally critical is enhancing infrastructure resilience through adaptive planning that accommodates localized subsidence variability, ensuring that transport corridors, utilities, and critical facilities retain operational integrity despite ground movement.

This latest research builds on Virginia Tech’s comprehensive efforts to understand urban flood and sinking risks across U.S. coastal cities. In a related study, the research team mapped flood vulnerabilities for 32 cities on the Atlantic, Pacific, and Gulf coasts, projecting conditions out to 2050. Additionally, they identified regions of the Atlantic coast sinking as much as 5 millimeters per year, emphasizing that subsidence compounds the effects of sea-level rise, necessitating integrated and proactive regional management practices.

Together, this body of research underscores subsidence as an urgent, if often overlooked, urban challenge with far-reaching consequences. By illuminating the invisible yet pervasive sinking beneath America’s cities, the Virginia Tech team calls for heightened awareness, innovative policy integration, and interdisciplinary collaboration among geophysicists, urban planners, engineers, and policymakers to safeguard the future of urban landscapes in a changing environment.

Subject of Research: Urban land subsidence driven by groundwater extraction across major U.S. cities and its impact on infrastructure and flood vulnerability.

Article Title: [Not Provided]

News Publication Date: 8-May-2025

Web References:

• https://www.nature.com/articles/s44284-025-00240-y
• https://news.vt.edu/articles/2024/01/research-sinkingcoasts.html
• https://news.vt.edu/articles/2024/01/COS-PNAS-subsidence.html

Keywords: Subsidence, Geophysics, Earth sciences, Climatology, Climate change, Climate data, Climate variability, Groundwater

The focus of the research is to evaluate soil conditions in these neighborhoods, which have been plagued by environmental hazards ranging from chemical spills to illegal dumping. The Sansoms have previously conducted similar studies addressing toxic elements in local soil, including lead and heavy metals in Houston’s Greater Fifth Ward. Their consistent engagement with community health concerns has solidified their roles as trusted voices in environmental research. The current project’s objectives extend beyond mere data collection; they encompass fostering a robust dialogue with local residents, thereby empowering those who are directly impacted by these environmental injustices.

Settegast and Lakewood are emblematic of the broader challenges faced by many urban neighborhoods, where socio-economic disadvantages intersect with environmental risks. Specifically, Settegast is home to approximately 4,800 residents, many of whom experience some of the lowest life expectancy rates in Harris County. This community is situated near landfills that contribute to severe environmental degradation; instances of illegal dumping and frequent flooding compound health risks. In Lakewood, hazardous sites and heightened air pollution levels further undermine public health, presenting urgent challenges that necessitate attention and intervention.

The project entails a thorough evaluation of the soil in these neighborhoods, focusing on the presence of cancer-causing heavy metals and polycyclic aromatic hydrocarbons. Upon identifying potential contaminant levels, the Sansoms plan to conduct comprehensive risk assessments that forecast long-term health implications for residents. The significance of determining soil quality cannot be overstated, as it directly correlates with community health outcomes. Heavy metal exposure has been linked to various health conditions, including neurological impairments and cancer, underscoring the urgency of this initiative.

Moreover, beyond the scientific analysis, the researchers intend to work closely with West Street Recovery, a community-based organization pivotal in guiding their engagement efforts. By collaborating with local leaders, the Sansoms aim to integrate residents’ perspectives and concerns into the research process, ensuring that the study’s findings align with community priorities. This relationship not only facilitates data collection but also cultivates trust, a necessary component when addressing sensitive issues of environmental justice.

Community engagement is paramount to reimagining the social fabric of neighborhoods like Settegast and Lakewood. By actively involving residents in discussions about environmental health, the project seeks not only to educate but also to empower. Residents bring invaluable insights into local environmental challenges, which can greatly inform the research efforts and subsequent interventions. Listening to community voices will help establish a clearer understanding of the issues at play, thereby optimizing resource allocation and fostering collective action toward solutions.

The broader implications of this project extend into the realms of sustainable urban development. Once the soil evaluation is completed, the results will catalyze a three-year initiative focused on creating an urban greenspace plan aimed at mitigating environmental pollutants. The concept of integrating green spaces into urban planning is increasingly recognized for its ability to improve air quality and, subsequently, community health. This endeavor aligns with national and international goals of fostering sustainable, livable cities that prioritize environmental health in the wake of rapid urbanization.

Addressing the challenges of environmental justice requires a nuanced understanding of the sociopolitical landscape affecting marginalized communities. For neighborhoods like Settegast and Lakewood, where institutional neglect has often dictated access to resources, research projects like this serve as crucial interventions that can challenge systemic inequities. By spotlighting these environmental issues and engaging local stakeholders, the work undertaken by the Sansoms may not only lead to policy changes but also inspire other communities facing similar predicaments to rise up and advocate for their rights.

The research investigators emphasize the project as a critical first step toward paving the way for healthier, more sustainable communities. As they prepare to embark on this scientific venture, their commitment continues to reflect a conscientious approach to addressing deeply rooted challenges faced by the residents. As environmental concerns become increasingly pronounced amid the realities of climate change, the insights gleaned from their efforts could well contribute to a broader dialogue on public health, environmental justice, and urban resilience.

In conclusion, the collaboration between the Texas A&M researchers and community-based organizations like West Street Recovery exemplifies a holistic approach to tackling the pressing issues of environmental injustice. The outcomes of their work could resonate well beyond the confines of the two targeted neighborhoods, potentially influencing policies that affect urban environments throughout the country. As the project unfolds, it will serve as a litmus test for the efficacy of integrating scientific research with community engagement, ultimately cultivating healthier, more equitable living conditions for future generations in Houston and beyond.

Subject of Research: Environmental Justice in Settegast and Lakewood Neighborhoods
Article Title: Addressing Environmental Injustices: A Comprehensive Soil Study in Houston Neighborhoods
News Publication Date: October 2023
Web References:
References:
Image Credits:

Keywords: Environmental Justice, Soil Evaluation, Heavy Metals, Community Engagement, Public Health, Urban Development, Settegast, Lakewood, Texas A&M University.