New Orleans is facing an unprecedented threat from its own foundation. A recent study by Tulane University researchers has revealed that parts of the city are gradually sinking, while the $15 billion post-Katrina flood protection system may need regular upgrades to outpace long-term land subsidence.

The study, published in Science Advances, used satellite radar data to track subtle shifts in ground elevation across Greater New Orleans between 2002 and 2020. The findings show that some neighborhoods, wetlands, and even sections of floodwalls are sinking by more than an inch per year – with some areas experiencing up to 47 millimeters (nearly 2 inches) of elevation loss annually.

“In a city like New Orleans, where much of the land is already near sea level, even minor drops in elevation can increase flood risk,” said Simone Fiaschi, lead author of the study and a former researcher with Tulane’s Department of River-Coastal Science and Engineering. “The findings underscore how both natural and human-driven forces are reshaping the city’s landscape.”

Causes of the sinking – known as subsidence – include natural soil compaction, groundwater pumping, industrial development, and the legacy of wetland drainage for urban growth. The study used a remote sensing technique called InSAR (Interferometric Synthetic Aperture Radar), which detects millimeter-scale changes in land surface elevation by comparing satellite radar images taken over time.

Among the most troubling findings: some of the concrete floodwalls and levees built to protect the city after Katrina are themselves sinking. In a few cases, parts of the Hurricane and Storm Damage Risk Reduction System (HSDRRS) are losing elevation faster than sea levels are rising, reducing their capacity to block storm surges.

“These results are a wake-up call,” said co-author Prof. Mead Allison, also of Tulane. “We need ongoing monitoring and maintenance to ensure that our flood defenses don’t lose their level of protection beneath us.”

The study also found pockets of sinking around industrial sites, the airport, and newer residential developments – areas where soil compression and groundwater withdrawal are likely contributors. In contrast, some areas such as parts of Michoud showed modest land uplift, likely due to the halt of industrial groundwater pumping and recovery of the water table.

Wetlands east of the city, long known for their ecological importance, are also sinking rapidly in places. In some spots, the loss of elevation could transform marshes into open water within a decade if trends continue. This has implications not just for wildlife but also for storm protection, as wetlands help buffer storm surges.

New Orleans, much of which lies below sea level, relies on an elaborate system of levees, pumps, and drainage canals to keep water out. As sea levels rise and the ground sinks, the margin for error narrows.

Experts say that without sustained monitoring, including satellite data and ground-based measurements, it’s difficult to know where to reinforce levees or how to plan for future storms.

“This research shows that land movement isn’t uniform, and understanding these patterns is crucial for protecting lives and property in a city where inches truly matter,” Fiaschi said. “However, it’s crucial to remember that our results still require careful ground-truthing. This is especially true for critical areas like the floodwalls, where on-site verification was not possible during this project.”

The study highlights the potential of satellite monitoring to guide infrastructure maintenance and urban planning, not just in New Orleans but in coastal cities worldwide facing similar challenges.

The Earth’s history is marked by periods of significant change, but one phenomenon that has been replicated across time is the release of massive amounts of carbon dioxide from natural earth systems. This process, dubbed an “ancient earth burp,” led to a crash in ocean oxygen levels some 300 million years ago, and experts warn that we are repeating this mistake today.

Research published in Proceedings of the National Academy of Sciences reveals that five periods when significant decreases in ocean oxygen concentrations (by 4% to 12%) coincided with significant increases in carbon dioxide levels in the atmosphere. These anoxic events had detrimental effects on marine life and biodiversity, and were likely most impactful on coastal regions.

“We’re creating a burp now at a rate two, maybe three orders of magnitude faster than in the past,” said senior author Isabel P. Montañez, a Distinguished Professor in the Department of Earth and Planetary Sciences at UC Davis.

The study used sediment cores from a geological formation in South China called the Naqing succession to analyze geochemical makeup and chronicle Earth’s environmental conditions from 310 to 290 million years ago. By analyzing the geochemical makeup of these deep-water cores, specifically carbonate uranium isotopes, the team chronicled Earth’s environmental conditions during this period.

The results showed that each period of decreased ocean oxygen lasted for roughly 100,000 to 200,000 years and coincided with pauses in biodiversity. “We do see these pauses in biodiversity each time these burps happen,” Montañez said.

The message from this research is clear: we should be cautious about the current human-driven release of carbon dioxide, as it could lead to a similar crisis. “Don’t be so sure that we can’t do this again with our current human-driven release of carbon dioxide,” Montañez warned.

This study highlights the importance of understanding Earth’s history and its relevance to today’s environmental challenges. By learning from the past, we can work towards creating a more sustainable future for all.

Wildfires have long been known to devastate forests and watersheds, but their lasting legacy is only now being fully understood. A recent study published in Nature Communications Earth & Environment has revealed that contaminants left behind by wildfires can persist in rivers and streams for up to eight years, posing a significant threat to water quality across the Western United States.

The research, led by scientists from the Cooperative Institute for Research in Environmental Science (CIRES) at the University of Colorado Boulder, analyzed over 500 watersheds across the region. The results showed that contaminants like organic carbon, phosphorus, nitrogen, and sediment can significantly degrade water quality in the years following a wildfire.

“We were trying to look at notable trends in post-wildfire water quality across the entire U.S. West, to help inform water management strategies in preparing for wildfire effects,” said Carli Brucker, lead author of the study. “Our findings suggest that water managers can use this data to plan for the future and respond appropriately when wildfires strike.”

The study’s principal investigator, CIRES Fellow Ben Livneh, emphasized the importance of understanding large-scale trends in water quality. “There’s been a lot of work on changes in global water supply,” he said, “but those assessments point to a gap in water quality assessments in a continental scale context.”

Researchers have long known that fire ash and soil destruction contribute to degraded water quality, but past research has largely been limited to state and municipal studies. This study took a more comprehensive approach, analyzing over 100,000 water samples from 500 sites: half from burned river basins and half from unburned.

The results showed that watersheds take longer to recover after wildfires than previously estimated, with significant increases in contaminants like nitrogen and sediment lasting up to eight years post-fire. The impact of wildfires on water quality varies greatly across river basins, depending on factors such as the location of the fire, soil type, vegetation, and weather.

“This study provides concrete numbers that give insight to water managers across the Western U.S.,” said Brucker. “We hope that providing real data will be impactful in informing future planning efforts for increasing wildfire resilience.”

As wildfires continue to pose a growing threat to forests and watersheds, this research highlights the urgent need for water managers to prepare for their long-term impacts on water quality.