Eelgrass is a long, wavy green plant that traps sediment, stabilizes the sea floor, and reduces coastal erosion. It sequesters four times more carbon than forests. It provides habitat for fish and shellfish, and produces the oxygen other underwater life needs. And it’s disappearing.
New Hampshire’s Great Bay Estuary saw a more than 80% decrease in eelgrass between 2024 and 2025, and in the upper part of the estuary, the Great Bay proper, that number jumped to 98%.
“Not that many years ago, there were really lush, beautiful beds of tall, healthy eelgrass growing in lots of places in Great Bay,” said Melissa Paly, the Great Bay-Piscataqua Waterkeeper working with the Conservation Law Foundation. “And that is gone.”
Paly says cycles of intense rain, along with pollution that flushes into the water during storms, have contributed to the decline.
“It’s like throwing a blanket on your garden that’s trying to grow,” she said. “It just makes it impossible for the plants to grow.”
Eelgrass is considered a foundational plant for estuaries. But the plant has faced major challenges in New England, dying off almost completely in the 1930s from a disease. Now, a mix of climate change and human development are threatening it again.
In the late 1990s, the Great Bay Estuary had about 2,500 acres of eelgrass. When researchers measured the population in 2025, there were only about 220 acres of eelgrass and widgeon grass combined. There was a slight increase in eelgrass in 2024, but that reversed significantly over the course of the last year.
Eelgrass can’t tolerate warm water, which poses an issue for the plants as oceans heat up. It also struggles when it loses access to sunlight, and when water quality deteriorates.
“People use it as an early warning,” said Kalle Matso, the director of the Piscataqua Regional Estuaries Partnership. “It’s oftentimes referred to as the canary in the coal mine.”
Matso said reducing pollution that runs into the water, trying to reduce runoff during storms, and conserving land would help the remaining eelgrass. But, he said, increasing restoration efforts like spreading eelgrass seeds might be the way forward.
“We've seen this in other parts of the globe, people have realized you get to a certain point and the system's not going to come back unless you start to get a little bit innovative and maybe a little radical,” he said.
