Oysters Part II: Decline of the Hudson

A few months ago, I read something that captured my interest. In the book Gotham Unbound, the author Ted Steinberg describes what Manhattan would have looked like hundreds of years ago.

As one of the largest estuaries on the East Coast, New York teemed with life: bears and wolves on the coast, eagles in the sky, whales in the harbor, thousands of fish species and migratory birds. He argues that if the U.S. had been settled west to east (rather than starting on the East Coast), Manhattan might have become a national park— more akin to Yellowstone. Instead, it became one of the greatest cities in the world.

Most people don’t think about New York as being an ecologically significant place. That aspect of its identity has become consumed by the city.

In Part I of my Oyster series, I explained the importance of oysters in their ecosystem as a keystone species. Each oyster filters up to 50 gallons of water a day and collectively, they form oyster beds which act as habitat for other fish and protect coastlines. Structurally, oysters were the backbone of New York Harbor— the abundant marine ecosystem that they facilitated was a key factor in the Dutch’s decision to settle here.

Today, New York Harbor is unrecognizable to what the Dutch had seen. There is a “chicken or the egg” problem when it comes to the death of New York’s 220,000 acres of oyster beds and the decline of the entire ecosystem. The reality is that the two events are impossible to disentangle.

In this edition, Part II: Decline of the Hudson, I explore the factors that led to this destruction. While not as uplifting as the topics I would prefer to write about, it is crucial to understanding where we stand in history and what the path forward may be.

There was no one event that led oyster populations to decline from billions to virtually zero. The problem was threefold and took place over ~150 years. The primary drivers were: (1) overharvesting, (2) poor infrastructure, and (3) industrial pollution.

Overharvesting

It’s quite remarkable to think that New Yorkers could have eaten their way through 220,000 acres of oyster beds. And to be fair, this wasn’t the only factor. But given oysters’ vast popularity at the time, overharvesting contributed significantly to the decline.

Oysters were sold out of carts around the city and were a staple for working class people. At the peak of the oyster industry between 1840-1860, it is estimated that New Yorkers were eating 600 million oysters per year. Given New York’s population at the time, that was 750+ oysters per person… which is remarkable.

The scale of oyster consumption was so great that shells were ground into mortar and used as pavement (hence the name Pearl Street in FiDi) and dumped en masse to fill in canals and expand the city’s coastline.

During this time, barges dragged iron rakes across the harbor floor, tearing up the oyster beds and any structures that sustained them. With no rest seasons or meaningful limits, beds that had taken centuries to grow were pillaged in decades.

Poor Infrastructure

New York’s appetite for oysters declined with the factor that ultimately served as the death blow to the native beds— pollution. With a ballooning population and no modern infrastructure, raw sewage was dumped directly into the Hudson and the East River daily. Obviously for oysters, being filter feeders, this is a problem. In the 1890s, New York Harbor oysters were tied to outbreaks of cholera and typhoid and by the early 1900s, oyster harvesting in New York Harbor had been banned.

It wasn’t until the 1970s that New York began to build what we would consider functioning waste treatment plants today. Still in 2025, during periods of heavy rainfall, untreated sewage is released directly into the Harbor.

Beyond the obvious health concerns posed by raw sewage in our water, this presents a significant ecological threat. This organic matter acts as fertilizer in the water, leading to blooms of algae. When that algae dies, it leads to a phenomenon called hypoxia (a state of deprived oxygen) which leads to the death of anything that requires oxygen (fish, oysters, etc.). If you have ever seen many fish washed up dead on shore, hypoxia was likely the cause.

This poor infrastructure and city planning was not unique to New York. Major cities all around the world have dealt and continue to deal with this problem. In the 2024 Paris Olympics, this was a key concern as they decided if swimmers could compete in the Seine.

This issue of contaminated water destroyed the oyster industry in New York. While overharvesting was an issue of its own, the disappearance of New York Harbor as a source of food meant that the ecosystem no longer served any purpose to humans on the island. With people not eating from the water and not able to fish, the life under water faded into a memory.

Industrial Pollution

The overfishing and the raw sewage was bad, but what followed is incomprehensible, devastating, and in many cases irreversible. The Hudson River and the East River became landfills for the largest city in a rapidly growing, rapidly developing country.

Through the 20th century, the world changed giving us many of the modern comforts that we enjoy today. It was a period of innovation and growth— the mass adoption of cars, the ballooning of the plastics industry, consumer culture, mass industrialization. That innovation, however, came with unforeseen consequences to both human and ecological health.

Upstream in the Hudson, General Electric was manufacturing electrical equipment. From 1947 to 1977, they discharged over 1.3 million pounds of PCBs (polychlorinated biphenyls) into the Hudson River. PCBs are long-lasting, fat-soluble industrial chemicals linked to cancer, autism, immune dysfunction, and reproductive issues. PCBs also accumulate up the food chain— meaning it binds to algae, small fish eat algae, bigger fish eat many small fish, and as a result the larger predators such as tuna accumulate PCBs. Due to their incredibly long half-life, PCBs released in the 20th century are still present in our food and ecosystems today.

In Tarrytown, where General Motors had a manufacturing facility, locals reported that you could tell what color the factory was painting cars that day by looking at the river. Paint runoff and solvents were sent straight to the water, leading to buildups of lead and other heavy metals, toxic to marine life.

In 1978, a Coast Guard helicopter spotted a large oil sheen on Newtown Creek in Greenpoint. An investigation found that over a 30+ year period, oil from Standard Oil (now ExxonMobil) and other gas companies had been leaking into the East River. The result was upwards of 30 million gallons of petroleum in the New York Harbor, making it the largest inland oil spill in U.S. history. Newtown Creek was deemed a Superfund Site in 2010.

The Domino Sugar plant in Williamsburg flushed hot wastewater directly into the East River, energy plants discarded coal tar and mercury into the water, and inadequate sewer infrastructure continued to dump raw sewage directly into the water.

The Consequences

Oysters which filter this water became contaminated with pollutants that affected their immune systems and stunted their ability to reproduce and produce shell. Buildup of organic material led to algae blooms and hypoxia— which suffocated the entire waterway.

The result was no more oysters. Overharvesting chipped away at the keystone species and pollution dealt the final blow. Over a 150 year period, the same estuary that for millennia had been a nursery for hundreds of fish species, habitat for humpback whales, and a key destination for migratory birds became a wasteland synonymous with pollution.

When you put it all in context, it becomes easier to understand how this destruction happened. It wasn’t one event. It wasn’t a series of subtle changes either. It was a prolonged onslaught of ecological abuses, each more shocking than the last.

You want to give those who contributed the benefit of the doubt— it was a different time and no one understood the ripple effects of what they were doing. But with the knowledge we have now, you can’t help but look back at this period in disbelief. How did this happen? How did they not know? Did they know and just not care?

In some way, these questions are a moot point now. All we can do is take stock. I wrote in my prior post that to follow the story of the oyster was to follow the story of the entire New York Harbor ecosystem. The decline is not a fun part of the story, but it is key to understanding why our waterways are suffering and allows us to find a path forward.