Evanston has cut down hundreds of trees in the last year and now is cutting 60 more, our stalwart mature Sycamores.
The key points of the Parks Department memo and the communication to the City Council are unsupported scientifically. They do not constitute a valid case for the tree removal program.
The cracks that they claim are mortal are normal, the cracks heal up in the spring and
summer, the tree is not mechanically or physiologically altered by radial
cracks to the trunk. Furthermore, the statement that the callus ridges
are normal growth structures is wrong. They are tissues that form during
the healing that follows a winter crack.
The current scientific classification of the Sycamore (Platanus occidentalis and its hybrids) cites the bark and trunk cracks as characteristic of the species, as an adaptation to the species relatively high seasonal water content and relative inflexibility of the wood. Also considered a species characteristic is that old Sycamores have hollow trunks. The cracks and hollows can be seen in the illustrations of typical, healthy Sycamores, and all the ancient Sycamores have these anatomical features. The statement that the winter cracks threaten the life of the trees because the deep ones would lead to hollow trunks, therefore, could not be further from the facts.
Sycamores are documented in the literature as able to live very long lives, as much as 2000 years. They have few mortal diseases and only are being replaced as ornamental specimen trees because of the aesthetic problem that athracnoes causes to the leaves and bark.
No scientific literature relevant to the issues is cited in the memo, and the stance of the Arboretum is misstated, as the Arboretum has no plans to remove its cracked Sycamores, and simply noted that the cracks are common. It is not the case that consultation to the Arboretum gave any support for the mass tree removal.
Here is what the botanist there advised "watching the cracks and waiting to see if they heal in warmer weather or get more severe. "As long as it's not a hazard, I'd wait for the spring to see how it leafs out. The tree needs to heal itself.
The Willmette forester noticed a number of cracks, but says "We don't remove every tree that has a frost crack."
And Chicago park officials, where Sycamores also developed cracks, said that they are waiting to see if the trees heal.
No other municipality is doing what Evanston is doing because it is not justified. The trees are not dead and have not been proved to be dying. Their removal is unjustified. By doing this they are churning our plantings by removing trees that may not now be fashionable but that are amongst the most durable, vigorous, and hardy trees for our area.
As for the "evidence", the link in the memo is not to a scientific source on Sycamore/Plane trees and their biological and ecological characteristics but just a random, non-peer reviewed posting on other species of trees. It is no way is sufficient information to justify the decision to remove all these trees.
Evanston would be advised to consult professional forestry literature on Sycamores, of which I cite several examples. It notes that Sycamores often develop splits in bark and cambium, but these regularly heal and do not adversely affect the survival of trees. The wood of the trees in fact has an interlocked fibrous structure that resists damage from splitting. Furthermore, trees are rarely harmed by insect or microbial attack except in crowded plantation conditions, according to Rousseau 2010 of the Mississippi University State Extension Service. The trees develop a strong structure of their own accord and rarely require corrective pruning, according to Gilman and Watson 1994, who recommend it for parkways. The trees coppice readily, recovering quickly and vigorously to lost branches and other cuts.
Sycamores, "strong, hardy, vigorous", according to the USDA and forestry service, are some of the longest lived trees and a very old species. Had people raced around to remove trees when they developed their normal, species-specific scars, there would be no very old Sycamores.
The town's justification for removal of my and others' Sycamores is invalid scientifically and practically. Proof of that is that Evanston is the only community that is doing this hasty, mass destruction of Sycamores.
Gilman, Edward F. and Dennis G. Watson
1994 Platanus occidentalis, Sycamore. Fact Sheet ST484, USDA Forest Service
2010 American Sycamore as a Biomass Species. Mississippi University State Extension Service, Publication 2636.
Wells, O.O. and R. C. Schmidtling
1990 Platanus occidentalis, Sycamore. National Forestry Service, Silvics Manual, vol 2. Hardwoods Agriculture Handbook No. 654. USDA Forest Service, Washington, DC.