Which forest is healthier? Lecture report by Christine Hume
Which forest is healthier? If you selected the first one pictured below you are on the right track. At the recent Mississippi Valley Field Naturalists (MVFN) talk “Coarse Meaty Debris: The Significance of Large Dead Animals in our Forests” given by Dr. Paul Keddy, we learned that a forest that has a healthy mixture of living trees, fallen decomposing trees, and dead standing trees is a healthy forest ecosystem. The talk focused on the deciduous forests of eastern North America.
Many of the forests in this area were cut by the end of the last century, so most of the ancient old growth forests are long gone. Slowly our deciduous forests have come back; some of the key indicators to help judge the health of these forests were discussed. The presence of diagnostic species such as spring ephemerals (e.g. Trillium), Wood Warblers and Salamanders are good signs. Additional indicators include: more big trees, canopy composition, a diverse herbaceous layer, wildlife trees, woodpecker nesting trees, and coarse woody debris. The woody debris is a major source of biological diversity, allowing ferns, mosses and fungi to thrive.
It is important for landowners with forested property to understand the benefits of maintaining and managing biological diversity. We learned that it is beneficial to a wide range of plants, animals and insects to let a tree that falls in the woods—just lie there. A general rule of thumb is to leave 8 fallen trees per acre—the bigger the tree the better!
Dr. Keddy then noted that as he was preparing the talk and thinking about the benefits of “woody debris” – the phrase “meaty debris” came to mind. The talk next focused on the importance of “coarse meaty debris” (animal carcasses) and the contribution it makes to a healthy forest. Of particular interest to me, was the description of the simple study conducted by Dr. Keddy and his wife Cathy on their property. On a beaver pond they set up a man-made carcass—a pile of trim (meat and bone scraps) from their local butcher. Then they recorded detailed field notes and observations over a period of 3 – 10 days noting which birds and mammals came to feed on the “carcass”. We were very surprised to learn that the first bird that came to feed on the meaty debris was a tiny little chickadee. It was feeding on the fat of the carcass. Next in the carcass line-up was a couple of crows, then turkey vultures, then a large gathering of crows and ravens; several coyotes and so on. It was a powerful demonstration of the number of species that will feed on carcasses and may depend on the availability of ‘meaty debris’ for survival.
The first bird to visit and feed on the ‘artificial’ carcass was a tiny chickadee. Photo Cathy Keddy
Another study that was conducted in Algonquin Park was presented— the ‘meaty debris’ in this instance included deer and moose carcasses. Species that eventually found the carcasses included: ravens, turkey vultures, fox, black bear, otter, and wolf. Black bears are known to be carrion feeders. There is a huge array of species that feed on carcasses. They are a centre of biodiversity. The bodies are cleaned up—animals may tear, grind, pick, gnaw and disperse pieces of the carcass. Anything remaining goes back into the soil. After a few weeks there is nothing left. Quite fascinating really!
It was also interesting to learn about the 68 species of burying beetles. The beetles bury small carcasses; lay their eggs in the carcass and their young then feed off of it. And then Dr. Keddy presented some examples of how humans can interfere with the circle of life – and keep it from running smoothly.
Given a total deer population for Ontario of 400,000, (estimated by the Ontario Ministry of Natural Resources), the range of deer i.e. covering about 40% of the area of the province, and a natural annual mortality rate of 10%, the natural deer carcass density would be approximately 1 carcass/10 km2. The annual removal of potential carcasses through hunting (60,000 – 70,000, estimated by OMNR) is high relative to the 40,000 animals that naturally become “meaty debris.” The removal of deer by hunting results in a steady drain of carcasses, nitrogen, phosphorus, and calcium from our forests. This probably has a significant negative impact on all the species that feed on carcasses.
And going back 10,000 years Dr. Keddy briefly discussed “megafauna” and the big carcasses of that era, now missing, including: woolly mammoth; sabre-toothed cat; giant ground sloth and more. The cause of the demise of these giant creatures at the end of the last ice age is widely debated. We saw photos of hand-chiseled spearheads that were found along with the remains of some of these gigantic mammals. It is suspected that our human ancestors became a bit too skilled at hunting and likely were largely responsible for exterminating the megafauna.
This talk really made me think of the circle or web of life – and how interconnected and interdependent the trees, plants, mammals, insects are on each other.
How can we contribute to keeping our forests healthy?
Find out what is being done with road kill that is collected? Instead of it being incinerated or disposed of, can some be distributed in managed forests to support a healthier ecosystem? Can some be put where naturalists can observe and learn the effects of meaty debris?
Increase public awareness that dead trees and carcasses in the woods are an essential part of nature— a “good thing,” not something to be offended by— they will be cleaned up by nature itself.
Resources: To learn more about our forests and the Managed Forest Program, check the Ontario Ministry of Natural Resources website at http://www.mnr.gov.on.ca/en/. If you are interested in volunteering and helping with forest management projects, refer to information provided by OMNR, the Ontario Forestry Association (http://www.oforest.ca/) and the Eastern Ontario Model Forest http://www.eomf.on.ca/ . For more information about the research work of ecologist Dr. Paul Keddy, please visit his website at http://www.drpaulkeddy.com/