Trees and Climate: Acclimation and Adaptation
We are doing a series on buds and shoot growth. Based on things I have read recently on Substack and elsewhere, I’m going to take a detour to discuss something exceedingly important with respect to trees and climate. Indeed, we can’t really discuss the response of trees to climate change without distinguishing between two very different responses: acclimation and adaptation.
I have worked for much of my career as a tree biologist on the conservation of very old trees. Many of the trees I work with in the woodland pasture ecosystem of the Bluegrass are 400 years old and some are older. We see a lot of wild guesses about tree age, but temperate trees leave annual rings as a record of their growth. Here are pictures of a few trees that I have come to know while working on my book Venerable Trees. In spite of the scars on their bark, these are all healthy, vigorous and very old trees.
When I became a university professor, I made a vow to myself never to give a public lecture about trees without discussing climate change. At the time, few of us even knew what it was, and I recall many in my audience being astonished that human activities were changing the climate. Today, we all know that climate change is real and is upon us, but we have done too little about it. If we are to conserve our trees and forests into the future, we must aggressively pursue remedies. The most important remedy is to stop burning fossil fuels. Improved understanding and management of our forests is also critical.
I have read hundreds of articles, both technical and popular, about tree responses to climate change. Many are quite good, including those in Substack. But there is something consistently missing from many accounts that prevents us from mitigating the impacts of climate change on trees. That something is acclimation.
The difference between acclimation and adaptation is crucial to our understanding of the response of trees to changing climate. Simply put, acclimation is change in physiology, adaptation is change in genetics.