Oysters for Earth Day
April 21, 2025 — "We do not inherit the Earth from our ancestors; we borrow it from our children." This Native American proverb could echo with new urgency this Earth Day, as environmental protections are rolled back and threats— from biodiversity loss to pollution— continue to mount.
Instead of sounding another alarm, which risks getting lost amidst so much doom and gloom, let’s focus on good news: oysters.
Last week, we spent part of spring break on a tour of Hog Island Oyster Farm. The enthusiasm of the marine biology graduate who gave us the tour was contagious, as she explained the measurable benefits that oysters bring to the Tomales Bay, California’s intertidal zone.
As we approach Earth Day this year, the farm tour plus a confluence of oyster learnings have us feeling more upbeat than usual. These unassuming bivalves are proving a powerful ally in the quest to restore ecosystems and give reason to celebrate.
Protecting Biodiversity
Overfishing, poor land management and coastal erosion have contributed to the loss of coastal habitats, vital for marine life. Yet oysters can help reverse this trend by stabilizing and rebuilding eroded shorelines.
Oysters naturally form dense colonies that create oyster reefs—hard structures that protect coastlines from erosion and safeguard inland infrastructure, such as homes, businesses and roads. For example, research from University of California Santa Cruz on the Gulf Coast shows that large-scale oyster restoration projects are the most cost-effective way to reduce flood damages over a 20-year period.
Oyster reefs act as buffers, reducing the impact of waves and storms, which can otherwise wash away vital coastal land.
Similarly, oyster reefs restore important habitats for a range of marine species, from fish to invertebrates. Our previous visit to Treasure Shellfish near Vero Beach, Florida, highlighted how floating oyster cages could revitalize biodiversity in a barren marina previously impacted by a hurricane.
Within six weeks, hundreds of thousands of oysters suspended in the water in floating cages by farm owner Nicoletta Mariano created an ecosystem anchor. Her oyster farm attracted new crustaceans and fish species. Mariano cited that she started to see bay scallops recruiting for the first time on the Indian River Lagoon too.
Nature’s Filtration System
Excessive nitrogen and phosphorus pollution from agriculture, sewage and industrial runoff can lead to algae blooms that deplete oxygen levels in the water, creating "dead zones," where marine life cannot survive. This pollution is devastating for water quality, fisheries, ecosystems and recreation, like swimming.
Oysters, along with other bivalves, act as natural filters to improve water quality. A single oyster can filter up to 50 gallons of water a day, removing pollutants, excess nutrients and organic matter from the ocean.
Oysters trap nitrogen and phosphorus in their pseudo-feces, which they deposit in the ocean floor, describes biologist Dr. Keryn Gedan, a GWU researcher who also runs The Gedan Lab.
Therefore, oyster lovers don’t have to worry. The pollutants are removed from the ecosystem indefinitely. This filtration process helps to clear the water, restore oxygen levels and create a healthier environment for marine life.
By reducing the harmful effects of pollution, oysters contribute to cleaner, more sustainable water systems, benefitting humans and sea life which rely on these habitats to thrive.
Mitigating Ocean Acidification
One of the most pressing challenges posed by climate change is the acidification of our oceans. As atmospheric carbon dioxide levels rise, about 30% of this carbon is absorbed by the oceans, leading to a drop in pH and making the water more acidic and disrupting marine ecosystems.
When oysters filter water, they remove organic matter and release hydrogen ions into the surrounding water, which helps to counteract the effects of acidification. This process, known as the “biogenic alkalinity effect,” can stabilize the pH of coastal waters. In low-lying marsh areas, where oysters best survive, they can buffer the water’s acidity, improving conditions for other marine species and helping to prevent further ecosystem damage.
A Call to Action on Earth Day: Harnessing Nature’s Power
As we approach Earth Day, it is crucial to remember the immense power of nature. Oysters, along with all bivalves and a broader focus on nature-based solutions, offer millennia-old solutions to tackle modern day challenges.
Examples from Galveston Bay, Chesapeake Bay, and the Billion Oyster Project show how reintroducing oyster reefs into our coastal ecosystems are really at the nexus of people, profit and planet.
From Hog Island to Long Island, we are deeply dependent on the natural world, and oysters are one more reminder of the value of working with, not against, nature.
Oysters may be small, but their impact is vast. By investing in, growing and eating more oysters and other sustainable seafood (using this Monterey Bay Seafood List as a guide), there is a way to harness the power of nature and create jobs and economic prosperity too.