Trees are Migrating, Creating Uncertainty for U.S. Ecosystems and Business

A recent article in the journal ScienceAdvances suggests a historic shift in forests -- specifically trees along the U.S. eastern seaboard. The study, co-written by professors and forestry officials, confirms much of what we already know: Climate change will send more plant species northward as they slowly seek to escape rising temperatures.

But as the temperature in the eastern U.S. rose 0.16 degrees Celsius (0.29 degrees Fahrenheit) over the past three decades, even more trees have moved westward than those that have migrated north. And while researchers say rising temperatures caused these various trees’ dispersion to shift, other factors are at play, including an increase in precipitation. The result not only presents an uncertain future for ecosystems across North America, but it could also disrupt businesses big and small.

The researchers, led by Songlin Fei of Purdue University, found that different types of trees respond to climate change in different ways. Gymnosperm trees, which include species like pines and firs, have seen their center of population move northward. In contrast, angiosperms -- which comprise deciduous trees such as oaks and maples -- are drifting westward as well. Both of these shifts happened at a remarkable rate, with species moving anywhere from 12 to 15 miles a decade on average. So, what exactly is going on?

A number of factors can explain this change, say researchers. Pine and fir trees are generally pollinated by wind. They are more sensitive to temperature fluctuations, but they generally are more resilient during times of drought than their oak and maple cousins. But deciduous trees, which usually rely on insects for pollination, are drifting west. And while the east coast has received more rain overall than a few decades ago, the west (which in this case means the “old west,” or Great Plains) is receiving more rain as well.

The problem is that this precipitation is coming in uneven intervals: Witness the ongoing droughts in the southeastern U.S., including Georgia, that ravaged farms and sent municipalities scrambling to ensure water supplies are secure.

Those trends back up this study -- which suggests that out of all the possible movements, only 2 percent of tree species have moved in a southeastern direction. In contrast, 73 percent of them moved west, though Fei told the Atlantic he is unsure whether that trend will continue. Considering the recent droughts that have scorched lands from Texas to California, therein lies an important question: What happens when these trees’ populations have no where else to go?

Fei and his team suggest that changes in precipitation patterns, more so than warmer temperatures, are responsible for the ongoing shifts in forest ecosystems. In order to understand these trends, they mined data from the U.S. Forest Service, which has consistently taken what can be described as a nationwide tree “census” since the late 1970s.

This Forest Inventory and Analysis program helps the Forest Service determine what forests will look like in the future and assess whether current practices are actually sustainable. Fei and his group of researchers did not rely on any statistical sampling – they did a full empirical study, so large tracts of federally managed land, as well as trees in city parks or those lining suburban developments, were evaluated during their research.

As is the case with this survey, more studies will be needed to understand the impact of these changes in the long run. On one hand, after years of deforestation, the total amount of forested areas in the U.S. has been on a slow rebound. But the southeastern U.S. has been one of the fast-growing metropolitan areas, and changes in land use could be a driving factor behind these trees’ migration. In addition, pests and blights could have had their share of impact, as well as successful conservation efforts. But as more tree species move north and west, they could also be susceptible to insect outbreaks, many of them due to invasive species, that have ravaged forests in northern states for several years.

The results could hit both large industries and more local companies. Local businesses that rely on outdoor recreation opportunities could see a hit if the local landscape changes, especially considering the correlation between insect outbreaks and wildfires in the U.S. west. The U.S. paper industry is probably safe, as unlike its competitors abroad, it relies on a wider variety tree species. Two paper companies contacted by TriplePundit said so far, this shift in forests has not had any impact on their long-term planning. But if forests begin to struggle, and their role as a vital carbon sink diminishes, there could certainly be future threats to agriculture, ranchland and as some scientists insist, public health.

If U.S. businesses are truly serious about taking on climate action, this study should serve as another example of a canary in the coal mine.

Image credit: Miguel Vieira/Flickr