Climate Change and Our Trees

Will it be Adaptation or Survival of the Fittest for our Trees?

Climate change is causing temperature averages to change, increased extreme temperatures and changing precipitation patterns. The changes have already begun to affect the trees not only in the Midwest, but worldwide.

Changing climate in ancient time was slow compared to the rapid changes currently, and there were slow shifts in tree ranges. The most sensitive species are already shifting their range, but the climate is changing so much more rapidly only time will tell if trees can adapt or shift quickly enough. Shifts of temperature and rainfall averages is not the only concern, temperature extremes and extreme storms could seriously damage our most sensitive species. Extinction of species is a valid concern. Loss of species and even migration of species will also affect the habitats of wildlife species. As the climate changes and the trees try to adapt or migrate, they are being stressed by the changes. Additional stresses from disease or pests will make it even more difficult to adjust.

Several species have already begun a northward migration in North America, moving to cooler northern regions or higher elevations. In some cases species are simply losing territory that they are able to thrive in. More southern species are able to expand into warming northern regions, but are not necessarily losing hospitable territory. Each species is behaving differently based on their range of tolerance. For example our Black Oaks might be expected to migrate north while being replace by White Oaks. However Black Oaks fare well after fires, experiencing moderately resistant to top kill but regenerates quickly from an opened canopy and may be able to retain their territory. Naturally repeated or intense wildfire could negate recovery.

In the Midwest we can expect, and are already experiencing, longer warmer summers and shorter winters. But this comes with more extreme drought, storms and floods, as well as extreme highs and lows. Our beloved backyard and boulevard trees could likely disappear from the region. To make matters worse, the warmer climate allows pests such as the Emerald Ash Borer to survive further and further north, rapidly decimating our Ash trees. To diversify our urban forest, city foresters are pressuring the nursery industry to propagate species that may be new to them in order to match evolving climate conditions. But along with “importing” species from other regions, we risk importing pests and disease that we are not equipped to deal with.

Some research indicates that certain genes will aid in adaptation to the changing environment. This allows for survival by natural selection within the species. This gives hope to species survival, rather than survival of only certain species. In the meantime, it is critical that we continue to monitor the species and diversify our forests, natural lands, parks and landscapes.