As skyscrapers rise along the shores and global trade surges, the world’s busiest coastal cities are running into a less-visible problem—they’re suffocating marine wildlife with boat traffic.

A new study, published in Marine Policy, offers a stark look at the underwater impact of urban growth, using China’s Greater Bay Area—which includes Guangdong, Hong Kong, and Macao—as a test case. This region, home to 86 million people and one of the busiest ports on Earth, sees an astonishing 6,000 vessels moving through its waters every single day.

“We found that marine species are likely exposed to relentless presence of vessels,” said researcher, Phil Doherty at the University of Exeter. “Put simply, boats and ships are everywhere, all the time.”

That constant churn means trouble for sea creatures. In shallow coastal waters, wildlife can’t dive deep to escape the noise, wake, and physical presence of human activity. According to the research, some conservation areas in the Greater Bay Area were disturbed on 95% of days during the five-year period they studied.

The study was conducted by ENSURE (Environmental Sustainability and Resilience Joint Center), a partnership between the University of Exeter and Chinese University of Hong Kong, and it drew on detailed vessel tracking data from 2013 to 2018.

While traffic may be great for economic growth, the environmental bill is coming due.

“In shallow waters like those of the Greater Bay Area, such traffic is likely to increase rates of shoreline erosion, turbidity (churned-up sediment), noise pollution and collisions with wildlife,” said Doherty.“The shallow water also means species cannot escape into the depths, leaving them little refuge.”

These impacts are not just hypothetical. The region’s marine habitats are home to species that are already vulnerable or endangered, including the Chinese white dolphin, the finless porpoise, and ancient survivors like Chinese and mangrove horseshoe crabs.

While the focus is on the Greater Bay Area, the implications are global. Coastal megacities—whether in Asia, the U.S., or elsewhere—are booming. As they do, their waterways face the same risks.

“Pressure on marine environments near coastal cities is only going up, and we need to think about how to limit human impact,” said co-author, Stephen Lang.

“With Hong Kong and Shenzhen hosting the busiest port in the world,” added Dr. Felix Leung from the Chinese University of Hong Kong, “the relentless pace of economic growth and development is taking a toll on the marine ecosystem.”

The researchers suggest practical steps that don’t require halting growth, but rather managing it wisely:

• Designate shipping lanes that avoid sensitive habitats
• Reduce ship speeds to lower noise and collision risk
• Encourage quieter, cleaner vessel technology
• Limit traffic in ecologically fragile zones

“To safeguard these ecologically sensitive areas,” said Leung, “governments must adhere to the Global Biodiversity Framework, ensuring both protection and sustainable management for future generations.”

The oceans don’t have a vote in city planning meetings, but studies like this make the case that they should at least have a voice. Protecting our oceans is a big part of protecting our human future for our children and national securities.

SDJ Lang et al. Spatial footprint of maritime vessels in the waters of a fast-growing coastal megalopolis. Marine Policy (2025). DOI: 10.1016/j.marpol.2025.106739