Vermont climate forester: simpler, younger forests are more vulnerable to pests, extreme weather

Al Freeman, climate forester for the Vermont Department of Forests, Parks and Recreation, told the House Agriculture, Food Resiliency & Forestry committee on Oct. 12 that Vermont’s largely young, regrown forests are more vulnerable to pests and extreme weather and need management that increases structural and species diversity.

“Forest resilient is the ability to withstand and recover from disturbances such as climate change, pests and pathogens,” Freeman said, defining the agency’s working concept of resilience as he opened the department’s presentation on forest and climate resilience.

Freeman said Vermont’s forest cover returned to roughly 80% of the landscape after large-scale clearing in the 1800s and early 1900s; because many stands developed around the same time, they often have “simple” structures with similar ages and species. Those simple forests, he said, have fewer recovery pathways than more structurally complex forests with diverse ages and species. That matters because climate change and other threats are increasing in speed and intensity. “Climate change is leading to greater variability, including precipitation,” Freeman said, and he told the committee to focus on timing, frequency and severity of storms rather than only annual averages.

Freeman laid out characteristics managers seek to increase resilience: species diversity and redundancy (so different species can fulfill the same ecological roles if one is lost), a mix of tree ages and sizes, structural complexity that creates microsites, adequate deadwood for nutrient cycling and nurse logs, and ample natural regeneration. He noted emergent threats including the Emerald Ash Borer moving across the state and “beech leaf disease that is knocking on our door.” He also warned that warmer winters can reduce insulating snow, increase freeze-thaw cycles that damage roots, and let some pests expand.

As examples of active work, Freeman described small-gap silviculture being used at Mount Mansfield State Forest in partnership with Audubon Vermont to favor bird habitat and desired regenerating species, and a Dartmouth-owned 27,000-acre project applying Adaptive Silviculture for Climate Change treatments: a mosaic of one-acre and smaller gaps, mature intact forest, and targeted thinnings to create habitat, support regeneration and supply local mills. He said some harvested trees from those treatments go to the LaMel Mill in Essex.

Freeman also described planned research plots created with the Northern Institute of Applied Climate Science and the University of Vermont to test replicated climate-adaptive treatments against control plots and monitor them on a 1-, 3-, 5-, 10-, 20- and 30-year schedule.

On planting and assisted migration, Freeman said planting is one tool but not a panacea: plantings can add functional nodes or traits (for example, sourcing seed from more southern populations), but many plantings have high mortality where spring droughts occur. “We’re not trying to plant and displace what’s already there,” he said; planting is “one of the many tools that we could potentially use depending on your site and the vulnerabilities of that site.”

Committee members asked about implications for sugarbush management, redundancy after historical losses such as chestnut, and practical day-to-day duties of a climate forester. Freeman said he spends time integrating climate resilience into state lands planning, developing planting guidance and conducting outreach with landowners and groups such as the Vermont Woodlands Association.

The presentation concluded with Freeman saying the department is pursuing funding to scale climate-adaptive work and to help landowners pay for practices that increase complexity and local forest economies.

Less technical, short-term points from committee discussion included questions about seed stratification needs under warmer winters and how specific pests like the hemlock woolly adelgid respond to milder winters.