A new study by the US Geological Survey shows that a nationwide effort to control acid deposition by reducing sulfur dioxide and nitrogen oxide emissions from power plants has worked, reversing decades of ecological damage and supporting significant recovery of brook trout populations in the Adirondack Park’s 30,000 miles of rivers, brooks and streams.
The study covered a period of more than 40 years, finding that Adirondack brook trout had repopulated streams once too acidic to support them. Of the 42 sites surveyed, more than half had no trout in 1984-89. By 2023 brook trout were living in 33 of the 42. Adirondack brook trout were one of signature species sampled in 42 streams across the Adirondacks.
“The national Acid Rain Program stands as one of the most significant environmental success stories since air pollution controls were implemented in the 1970s,” said Adirondack Council Executive Director Raul J. Aguirre. “Before these efforts were undertaken, every trend was negative: fewer fish, smaller fish, and widespread losses, particularly of cold-water species such as brook trout. The program worked faster and more effectively than anyone anticipated, and at a fraction of the cost originally predicted.”
“While this is a victory for the Adirondacks and for brook trout, it is also an important reminder that it took forty years of bipartisan federal support to get here,” Aguirre said. “By weakening emissions and fuel-efficiency standards through regulatory rollbacks, the US Environmental Protection Agency risks reversing these gains and bringing significant harm to the Adirondacks.”
The peer-reviewed study, commissioned by the New York State Energy Research and Development Authority (NYSERDA), appeared first in the December 2025 edition of Freshwater Science, published by the University of Chicago Press.
The findings were released just as the US EPA announced it was weakening some smokestack regulations. And on Tuesday this week, the EPA announced it would no longer consider the financial benefits of saving human lives and preventing human disease when it decides whether a regulation is too costly for industry.
Between 1984 and 2023, as acid rain was declining:
The total number of fish species living in Adirondack streams rose by 112%
The total number of fish per cubic yard of water increased by 236%
The total weight of fish in the stream rose by 66%
Levels of fish-killing toxic metals (i.e., aluminum) in the water also declined sharply
The conclusion of the new report showed that rain and snow falling on the Adirondacks is more than 10 times less acidic than it was in 1990 when the Acid Rain Program, Cross-State Air Pollution Rule, and other current regulations first began.
That has led directly to improvements in water quality, which in turn have led to a greater diversity of fish species, more brook trout, bigger fish in general, and more streams with brook trout in them, the report noted.
DEC recently announced that about 90% of brook trout pond habitat has been lost due to poor management, however.
Cap & Trade
The program’s system of rewards via cap-and-trade allowances for curbing emissions faster and deeper than the law required helped it succeed, Aguirre said. Noting that cap-and-trade emissions reductions could be expanded to the task of curbing greenhouse gases.
Currently, New York and nine Northeast states from Maine to Maryland participate in a Regional Greenhouse Gas Initiative (RGGI) cap-and-trade program that has reduced power plant carbon emissions by 50% since 2005, while generating over $10 billion for clean energy and green jobs development in local communities, according to RGGI.
Gov. Kathy Hochul has announced a pollution cap-and-trade program to help New York meet the goals of the state’s Climate Leadership and Community Protection Act. Last fall, she announced she was delaying the rollout of that program for a year.
The Adirondack Park contains one of the largest intact temperate forests left in the world and is home to approximately 130,000 year-round residents. The Council advances its mission through research, education, advocacy, and legal action. It envisions an Adirondack Park with clean air and water, core wilderness areas, working forests and farms, and inclusive, thriving communities.
Photo of Benjamin Ferguson with his 2025 state record brook trout provided by DEC.
Recent Comments