Why are old-growth forests important?

When thinking about healthy forests, it’s not often that we think about dead, dying or diseased trees but any forest manager will tell you that they’re an essential part of a healthy forest ecosystem, and a key characteristic of old-growth.

Dr. Bill Freedman, a professor of biology at Dalhousie University in Halifax, Nova Scotia, and Chair of the Nature Conservancy of Canada’s (NCC’s) National Board of Directors, explains that “old-growth forest contains some large and old trees, but all age classes are present.” Old-growth forests exist because they have not been subjected to a significant disturbance such as wildfire or clear-cutting for a century or more. Overall, it’s not easy to pin down an age at which a forest becomes “old,” because depending on the climate, geography and soil, a forest’s composition and lifespan will vary drastically.

So what makes old-growth forests unique, and why are they important? The first answer is that old-growth forests contain trees in all phases of their life cycle, from saplings, to mature trees, to dead standing trees and finally, as rotting trees on the forest floor. This provides a home for many species of plants, fungi, invertebrates, salamanders and snakes, and makes old-growth forests hotspots for biodiversity and a refuge for high concentrations of species at risk.

“Protecting old-growth forests means respecting the elders, letting them die a natural death and crash down, even if they’re diseased,” notes Mark Stabb, NCC’s Central Ontario Program Manager. Dead trees significantly change the structure and composition of the forest, but there are always saplings waiting in the shadows to take their place. “This helps us understand how they will respond to disease and natural disturbances such as fire, tornadoes or earthquakes,” says Stabb.

“There aren’t many old-growth forests left compared to a couple hundred years ago,” he adds. But the 200-year-old Happy Valley Forest (HVF) Natural Area in Ontario is a good example of a forest that is growing old. Located just 35 kilometres from Toronto, this 2,851-acre (1,154-hectare) forest is an outstanding example of mature Sugar Maple and beech forests characteristic of the Oak Ridges Moraine. The HVF is critical habitat for over 110 breeding bird species, including the nationally significant Acadian Flycatcher and Cerulean Warbler and amphibians like the Jefferson Salamander.

Dr. Henry Barnett, whose land NCC helped protect in the HVF and who has been instrumental in convincing neighbours to put their land under conservation protection, remarks, “with more than 210 acres (85 hectares) protected so far, hopefully the Happy Valley Forest will have a chance to become truly old-growth in the years ahead.”

Provided by Nature Conservancy Canada

www.natureconservancy.ca