With more than just rising temperatures and extreme weather events, climate change is also a grave threat to the health of the forests of the northeastern United States, thus having implications for military readiness and national security. According to the most recent US National Climate Assessment, winters in the Northeast have warmed at three times the rate of summers in recent years, causing a radical decline in winter snowpack. The implications are running deep for forest ecosystems, very vital for environmental stability and military operations.
Historically, much of the Northern Hemisphere has remained snow-covered during winter months. Now, however, warmer temperatures are reducing depth and duration. Decades of research, including implications of winter climate conditions, has emerged as a key regulator of forest health. Reductions in snowpack compromise the health of trees and diminish the ability of forests to filter both air and water, with cascading impacts on military training grounds and operational readiness.
Most at risk are the northern hardwood forests that blanket a broad swath of 85,000 square miles extending from Minnesota into the northeastern United States. Characterized by sugar maple, yellow birch, and American beech, these forests provide key ecological services in carbon storage and water quality while supporting a suite of industries from timber to maple syrup that is integral to the local economy and, by extension, the communities supporting military installations.
Research from the Hubbard Brook Experimental Forest in New Hampshire-one of the longest-running studies of its kind- indicates that a declining snowpack is increasing the likelihood of soil freeze-thaw cycles. These cycles can damage tree roots and result in reduced tree growth and forest carbon storage. Whereas the snow had been removed, it reached a foot or more into the soil, while in plots with natural snowpack, frost penetrated just two inches. That root damage starts a cascade of ecological responses which also involve increased carbon dioxide emissions from soil and reduced nutrient uptake by trees.
The implications for military operations are huge. Less productive and less healthy forests could impact resource availability and the reliability of training locations. For example, sugar maples, which may comprise more than half of annual forest biomass accumulation at Hubbard Brook, experienced a 40 percent growth reduction when the snowpack was removed. This decline in forest health can degrade the effectiveness of camouflage and natural cover, important components for training exercises and operational readiness.
A new Dartmouth study shows that human-caused warming is decimating winter snowpack across the Northern Hemisphere. In New England, many river basins are losing 10 percent or more of their snowpack per decade. The immediate consequences will be more frequent rain-on-snow events, early snow melt shortly after falling, and also more days with bare ground. These kinds of conditions could pose military logistical and operational challenges, particularly in areas dependent upon snow cover for specific types of training and operations.
One of the researchers, Justin Mankin said, New Hampshire’s wonky weather is “emblematic” of broader trends that are hitting the region’s snow. The chances of storms bringing rain instead of snow, or warm snaps thawing out accumulated snow, begin to rise exponentially as average temperatures approach the freezing point. That in turn can mean less meltwater running down rivers and streams in the spring when it’s most needed.
If it continues, warming in the northeastern United States would probably lead to a near-permanent loss of snowpack, a factor that might significantly affect forest health as well as military readiness. When the stability of our natural and operational environments is in question, the need for adaptive strategies to mitigate its effects can no longer be delayed.