Eastern brook trout, photo from Trout Unlimited
This article first appeared in the Charlotte Observer on Feb. 27, 2012.
A spot of good news is surfacing for North Carolina’s brook trout, and the anglers who hold their speckled brookies so dear.
Not so long ago, scientists forecast that much of what remained of eastern brook trout habitat would be severely affected by climate change. In fact, it was thought the only native trout in the Eastern United States might vanish from large parts of its southern range, leaving only a few populations concentrated mostly in western North Carolina.
But a new study in progress across seven Southeastern states has found reason to believe that many cold-water streams – those found at elevations where brook trout love to linger – may be less vulnerable to warming temperatures than previously forecast.
The study’s investigator, Andrew Dolloff, is team leader for the cold-water fisheries research unit of the Forest Service’s Southern Research Station in Blacksburg, Va. Brook trout are very sensitive to water temperatures, preferring to live in the cleanest cold water streams below a critical threshold of 69.8 degrees.
“They can survive above this threshold, but making a living is much, much more difficult for them,” Dolloff said.
Brook trout are also one of the most widely spread temperature-sensitive aquatic species in the East. This makes them good indicators for understanding the effects of climate change. “If a trout can’t live somewhere anymore, there’s going to be a whole bunch of other species that can’t live there either,” Dolloff said.
In 2006, Trout Unlimited released a report that showed a 20 percent reduction in the historic range of brook trout. Trout Unlimited is a not-for-profit organization which protects, conserves and works to restore cold-water streams and rivers in North America. The report also showed that brookies were greatly reduced in an additional 47 percent of their historic range. This led some to question what the future might hold, given predictions of a warming world.
An answer to this question came about, also in 2006, when scientists attempted to scale down findings from a continental-scale model of climate change. The model assumed a correlation between water and air temperatures of about 0.8 degrees. This meant that for every one-degree change in air temperature, they modeled a 0.8-degree change in water temperature.
Most climate-change models predict about a four degree increase in air temperature in the next 100 years, so the study predicted a corresponding 3.2 degree increase in cold-water stream temperatures over the same period. This resulted in a dire forecast that the brook trout’s remaining habitat would contract radically, leaving intact less than half of the habitat that remained.
“It caused a lot of consternation, and rightly so,” Dolloff said. Continue reading →