Can our forests survive global warming?

by Leslie Helmuth

Pine beetles and wildfires

When I was in the Colorado Rockies in late August for a family vacation, I was stunned by a disturbing change in the panorama.

Large patches of the mountains near Grand Lake, where I had vacationed as a child, had turned from evergreen to gray, a telltale sign of the destructive toll of the mountain pine beetle. Warmer temperatures have allowed the invasive insects to spread mightily, killing millions of acres of pine trees in the West.

Pine beetle damage in Montana; photo courtesy Forest Service Northern Region

This fall, wildfires in my home state of Texas are likely to kill 1.5 million trees in 1 county. And a quick look at the Forest Service’s Active Fire Mapping Program reveals there are currently more than 20 fires throughout the drought-stricken West.

Back here in New England, as the leaves begin to change hue, I find myself slowing down to observe the thick stands of oaks, maples, and hemlocks.

Forests have destructive cycles, I know. Infestations and fires are part of their ecology. But many scientists say the rate at which forests around the world are declining is alarming. And there’s concern that some may not recover. With the loss of these woods comes the loss of carbon-absorbing trees—at a time when we really can’t afford to be without them.

The global warming effect

A recent New York Times article, With Deaths of Forests, a Loss of Key Climate Protectors, analyzes the evidence of climate change among forests globally. At the root of it all, reports Justin Gillis, is the water stress from rising temperatures (snow packs melt earlier, trees become drier in late summer, and they become easy victims for beetles and wildfires).

Interestingly, here on the East Coast warmer temperatures have resulted in longer growing seasons and, hence, some healthier forests. Among these is the Harvard Forest, a closely studied thicket that has resurged since early farmers abandoned it for the more fertile Midwest.

Gillis writes, “Today, the re-growing forests of the Eastern United States are among the most important carbon sponges in the world. In the Harvard Forest, the rate of carbon storage accelerated about a decade ago.” New forests could eventually take over northern terrain covered by tundra and grasslands, Gillis reports. But there’s not near enough land for new forests alone to offset our carbon output.

That being said, forests still absorb a billion tons of carbon annually. But there’s enough evidence of declining forests to cause concern. Researchers around the world are working tirelessly to observe these patterns more closely, to better understand the trends of forests over time. The Times article is a fascinating read, if you have the time.

Addressing the threat to forests around the globe is a huge undertaking. But you can do your part for the planet by reducing your carbon footprint. See the National Resources Defense Council’s simple steps guides.

Forest events at Harvard

If you’d like to learn more about the ecology of forests, their environmental contributions, and the threats they face, the Harvard Museum of Natural History is currently hosting an exhibit and a couple of lectures this fall.

• New England Forests exhibit
• The Emergent Forest of New England lecture, 6 pm, October 27
• How Much Can Trees and Forests Slow the Global Warming Increase?, 6 pm, November 9
• New England forest videos

Related Harvard Extension School courses & programs

• ENVR E-142/W Conservation Biology and Sustainable Use of Forested Landscapes
• BIOS E-120 Trees and Forests in New England
• Graduate Program in Sustainability and Environmental Management
• Sustainability Certificate