Forests are much more valuable than many people realize. They provide us with a wealth of health benefits and renewable resources, as well as protection from environmental dangers like flooding, erosion, pollution and climate change.

Even the toughest forests have their limits, however, and the speed of climate change is now testing them in many parts of the world. Some forests are struggling with drought or disease as weather patterns shift, and some are migrating to follow their traditional climates. And, as a recent 30-year study suggests, some are losing biodiversity in ways that could lead to big ecological and economic problems.

That study, published in the Journal of Applied Ecology, focused on a transformation in hardwood forests across the northeastern U.S. and southeastern Canada. Using three decades of U.S. Forest Service data, it found that climate change is altering the balance of these forests by helping one native tree species dominate three others.

American beech tree, Fagus grandifolia The roots of an American beech tree at Pennsylvania's Texter Mountain Nature Preserve. (Photo: Nicholas A. Tonelli/Flickr)

Climate-related changes are boosting the abundance of American beech trees, the study's authors report, while reducing the prevalence of sugar maple, red maple and birch. This is turning the region's beech-maple-birch forests into beech-dominated woodlands, a shift that could have significant ecological consequences.

American beech is a natural part of these forests, not an invasive species, and it does have key roles to play in its native habitats. Yet it's only one part of those ecosystems, and may be ill-equipped to fill voids left by the struggles of other tree species.

Beech is often used for firewood, as the Associated Press points out, but it has less commercial value than certain birch and maple trees, whose wood is considered better for furniture and flooring. There's the issue of beech bark disease, too, a fungal infection that kills the wood and stops the flow of sap. Affected trees tend to weaken and die young, replaced by new seedlings that eventually meet the same fate. Beech trees are also known to limit natural regeneration of other species, which may already face more pressure from deer that prefer to eat non-beech seedlings.

American beech tree nut American beech nuts are a valuable food source for many birds, mammals and other native wildlife. The decline of other native trees, however, still raises concerns about the biodiversity of their ecosystems. (Photo: Plant Image Library/Flickr)

The shift toward beech is associated with higher temperatures and precipitation, the study's authors explain, trends linked to climate change. (Although climates naturally change slowly over time, the rate of human-induced climate change is outpacing some species' ability to adapt.) Climate change is also known to harm already-sensitive species while disproportionately favoring more flexible rivals, the researchers add, so the beech boom has likely been boosted by other factors along with climate change, like suppression of wildfire or beech's natural adaptability.

The effects are still unclear, the authors note, since this is one of the first studies to examine broad, long-term changes in the region's forests. More research will be needed, but the forests will likely need help in the meantime, too.

"There's no easy answer to this one. It has a lot of people scratching their heads," study co-author Aaron Weiskittel, a professor of forest biometrics and modeling at the University of Maine, tells the Associated Press. "Future conditions seem to be favoring the beech, and managers are going to have to find a good solution to fix it."