Over several decades in the past century, city populations swelled as Americans moved away from rural forests. Now the forests are moving farther away from Americans.
A new study of satellite images taken over 10 years starting in 1990 shows the rural forest canopy disappearing. Forest space disappeared from the United States in such big chunks that the average distance from any point in the nation to a forest increased by 14 percent, about a third of a mile.
While that’s no big deal to a human driving a car with a pine-scented tree dangling from the rearview mirror, it is to a bird hoping to rest or find food on epic seasonal flights across the globe, according to the study published Wednesday in the journal PLOS One.
But forests aren’t just for the birds. They improve the quality of life for fauna and flora, from bears to flowers. Altering forests can change the dynamics of ecosystems and can potentially “affect water chemistry, soil erosion, carbon sequestration patterns, local climate, biodiversity distribution and human quality of life,” a statement announcing the report said.
Using forest maps over the continental United States, researchers Sheng Yang and Giorgos Mountrakis of the State University of New York at Syracuse marked tree canopy that disappeared over a decade in red to highlight the change. In one illustration included in the study, the page appeared to bleed.
“So if you are in the western U.S. or you are in a rural area or you are in land owned by a public entity, it could be federal, state or local, your distance to the forest is increasing much faster than the other areas,” Mountrakis said. “The forests are getting further away from you.”
One of the findings of the study is a twist that Yang, a graduate student, and Mountrakis, an assistant professor at the College of Environmental Science and Forestry, didn’t anticipate. The disappearance isn’t happening in cities, where people often complain about the uprooting of trees for development. It’s happening in rural America, where trees are falling and hardly anyone hears.
That finding turns conventional wisdom about forest loss on its head, Mountrakis said. “The public perceives the urbanized and private lands as more vulnerable, but that’s not what our study showed,” he said. “Rural areas are at a higher risk of losing these forested patches.”
“Typically we concentrate more on urban forest,” said Sheng, “but we may need to start paying more attention — let’s say for biodiversity reasons — in rural rather than urban areas. Because the urban forests tend to receive much more attention, they are better protected.”
While people in the sticks are losing their forests, the relationship between urban dwellers and trees is a love story. Dating back to when President Thomas Jefferson denounced the removal of trees that cooled the new capital city as “a crime little short of murder,” Jill Jonnes wrote in her book, “Urban Forests,” city slickers have fought to defend the little green space they get.
Rock Creek Park in the District of Columbia, Central Park in New York, Piedmont Park in Atlanta, Griffith Park in Los Angeles, and Golden Gate Park in San Francisco are examples of urban forests that are fussed over, pampered and protected by law. They are also cherished gathering places that help define their cities.
The remote areas that Americans have come to know as wild lands are being whittled away by farms, development and wildfire, particularly in the West, Mountrakis said. Arizona, Colorado and Nevada saw significant attrition or separation of forests, according to the satellite images.
In California and Colorado, trees stressed by drought are being eaten to death by beetles, standing dead on mountainsides by the hundreds of millions, virtual ghost forests. Ecologists argue whether fires that might consume them are a good or bad thing, in that it would kill the beetles yet threaten homes too close to the forest edge. Human development is another grim agent of tree canopy loss.
The researchers said they hope public land managers, such as the U.S. Forest Service and Bureau of Land Management, along with officials at the state level, will pay attention to their research. They hope to follow up the study with research into the drivers behind the loss of forests.
But the pictures don’t lie, he said. There’s no doubt that huge clumps of trees are disappearing.
“You can think of the forests as little islands that the birds are hopping from one to the next,” Mountrakis said. The loss of forests has side effects. It alters the local climate, decreases biodiversity and leads to soil erosion. “This is the major driver — we can link the loss of the isolated patches to all these environmental degradations,” he said.
The study tracked the loss of forest by calculating the distance to the nearest forest from all points on an area map, Mountrakis said. They noticed that some chunks of tree space disappeared within a forest, but that has less of an environmental impact as forests that wither on the edge, slowly transforming them into islands.