The Importance of Big, Old Trees
In the December 2012 issue of Science, American Forests Science Advisory Board member Dr. Jerry F. Franklin published an ecological study, “Global Decline in Large Old Trees,” with his colleagues Dr. David Lindenmayer and Dr. William Laurance. Dr. Franklin kindly sat down with American Forests staff members to discuss the study and the importance of big, old trees.
What exactly is a big, old tree? “Each forest has its own definition of what is large and what is old,” Dr. Franklin explains, “but we’re generally talking about trees that are over 150 years of age, and often, we’re talking about trees that are many centuries old.” And it’s this age, more than their size, that makes these trees so vital to the forests they call home.
“Big, old trees are not simply enlarged versions of young trees,” says Dr. Franklin. He says that this is the key point of the research and paper: to educate forest managers and the public on the impact that old trees have on an ecosystem’s health. One of these major impacts is on wildlife.
“Big, old trees have suffered the slings and arrows of climate, insects and diseases, and so they typically have a lot of features like cavities, which are really important from the standpoint of wildlife.” Various animals can use these cavities as living spaces. Dr. Franklin describes the struggles his co-author, Dr. Lindenmayer, is observing in Australia, where old trees are declining and younger trees simply don’t have the cavities to support wildlife. Unlike in North America, where woodpeckers can help form cavities in younger trees, Australia does not have any cavity-making wildlife. Only time and wear-and-tear can create these niches in the country’s trees.
Because of big, old trees’ irreplaceable role in forest health, Dr. Franklin believes strongly that we need to be developing forest plans to create diverse-aged canopies throughout our forests. “I’m really trying to get everybody to understand that we really need all elements, all stages of successional development of forests on our federal forest landscapes,” he says.
Related to this is developing forest policy that recognizes the importance of not just saving, but restoring old-growth trees and forests. “In this country, we really don’t have forest management policies that call for either retaining or restoring or maintaining populations of big, old trees [such as the ponderosa pine forests of the Pacific Northwest],” Dr. Franklin relates. “Now, in various parts of the National Forest System, we don’t log them anymore. … We save some old-growth forests. … But we don’t have a policy that says we recognize that the big, old trees are a structural element of our forests that we want to retain and restore where we’ve lost it because it’s important to the completeness of these ecosystems.”
What would such policy look like in action? “Where we’ve got them, we keep them,” advises Dr. Franklin. “Where we don’t have them, but we have intermediate-aged stands, we manage some of those stands or some of the trees within the stands in a way that’s going to lead to the development of large, old trees.” Dr. Franklin cautions, though, that this isn’t about creating huge stands of old-growth-only forests: “You really need all stages of successional development of forests in our federal forest landscapes. … We need to be thinking about the early stages of succession, as well as the old stages.”
Dr. Franklin explains that the first step toward protecting and restoring big, old trees is getting people to recognize their importance: “Big, old trees aren’t just objects of oddities and objects of interest. We need to have populations of big, old trees present in much our forest landscape in order to provide the kinds of habitat that we need for a lot of our wildlife.”
It sounds simple enough, but one thing that more than 100 years of forest policy and advocacy work has taught us is that nothing is easy when it comes to policy, but that doesn’t mean it isn’t a fight worth having. Thank you to Dr. Franklin for taking the time to chat with us. To read the complete Science article, “Global Decline in Large Old Trees,” visit sciencemag.com.