Black ash wetlands lost carbon after both borer-like dieoff and intervention

A 12-year Minnesota experiment separates immediate carbon accounting from the long task of replacing an ash canopy.

Wild Lands Ecological Intelligence Editor
Wild Lands Institute · 30 October 2026

Black ash wetlands lost carbon after both borer-like dieoff and intervention — Monica Tomosy/USFWS — illustrative U.S. wetland, NOT the northern Minnesota black ash study site · Public domain — U.S. Fish & Wildlife Service · Rights: Public domain

Evidence: Peer-reviewed
Geography: Northern Minnesota, USA
System: Black ash wetland forest; pest disturbance; carbon stocks

WHAT THE EVIDENCE SAYS

Across experimental black ash wetlands, scientists compared undisturbed controls with girdling as a proxy for emerald ash borer mortality, clearcuts and group selection of about one-fifth of canopy. Twelve years later, all treatments contained less total ecosystem carbon than controls, with the greatest loss after clearcutting. Girdled sites held about 22% less total carbon and substantial decomposing deadwood. Soil-carbon differences were variable and not statistically detected.

WHY IT MATTERS / OUR READ

The carbon outcome depends on living biomass, stored deadwood, regeneration and time. Neither leaving ash to die nor removing it automatically substitutes for establishing a healthy successor canopy; compare management options with long-term carbon and habitat objectives.

CAVEATS / UNCERTAINTY

Girdling imitates tree mortality but not every mechanism of an actual borer outbreak. The 12-year experiment does not determine eventual soil-carbon trajectories or establish one universal harvesting prescription.

SOURCE

Ecosystems — Clark et al., 29 October 2026
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