For decades, acid rain ravaged brook trout populations in some of the Adirondacks’ coldest, cleanest waters. Waterbodies that once held native fish turned sterile, their chemistry tipped too far out of balance to support life. Now, after more than 40 years of coordinated efforts, the trout are coming back, according to new survey results.
The research looked into nationwide levels of sulfur dioxide and nitrogen oxide emissions over time and how they have affected brook trout numbers in the Adirondack Park. Turns out, decreases of emissions, due to reduced output of pollution from power plants, has reversed decades of acid deposition in streams across the park. This in turn triggered a widespread recovery of brook trout across the Adirondack Park.
Long Term Study
The research tracked changes in water chemistry and fish populations in 42 Adirondack streams over more than four decades. In the late 1980s, more than half of those streams held no trout at all. By 2023, brook trout were present in 33 of the 42 sites. In other words, streams that were once too acidic to sustain brook trout were now sustaining them.
“The national Acid Rain Program stands as one of the most significant environmental success stories since air pollution controls were implemented in the 1970s,” Raul J. Aguirre, executive director of the Adirondack Council, said. “Before these efforts, every trend was negative—fewer fish, smaller fish, and widespread losses, especially among cold-water species like brook trout. The program worked faster and more effectively than anyone anticipated, and at a fraction of the cost originally predicted.”
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According to the study’s conclusions, the rain and snow falling on the Adirondacks these days is more than ten times less acidic than it was in 1990, when acid rain regulations first took effect. Cleaner precipitation led to healthier water, which in turn allowed more species, such as brook trout, to repopulate areas where they had died off.
Big Efforts for Small Fish
Aguirre cautioned that while the recovery is real, it was not quick or accidental.
“This is a victory for the Adirondacks and for brook trout,” he said, “but it’s also a reminder that it took forty years of bipartisan federal support to get here. Rolling back emissions and efficiency standards risks undoing hard-earned gains.”
What’s Next For Adirondack Brook Trout
Acid rain is not the only threat that native brook trout face in New York. In a region known for its cold, crystal clear lakes, a study from Cornell University said that Adirondack lakes are getting warmer and browner.
Known as “lake browning,” that means that lake surface waters are warming and the amount of vegetative matter in them is increasing. This traps heat at the surface and can decrease oxygen in the waters. For brook trout that inhabit Adirondack lakes, this is bad news.
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New York is only one of two states in the country that has cold-water lakes that sustain brook trout populations. The other state is Maine.
