By William Mullen
Chicago, IL (June 17, 2010)- As a tree scientist, Edith Makra spends her days at the Morton Arboretum thinking about, studying, planting and protecting trees – a subject she finds so compelling that her idea of the perfect vacation is to hike California’s redwood and sequoia forests with her husband. In 1993, as Mayor Richard Daley’s first urban forestry aide, she convened a groundbreaking census of trees in the city’s “urban forest,” as well as across Cook and DuPage counties. A part of Daley’s earliest city “greening” campaign, the undertaking called attention to disappearing native species like oak and years later aided in the battle against emerald ash borer beetles.
U.S. Forest Service scientists developed analytical software for the 1993 census. It was so successful that it has since been used in more than 300 cities. Now it’s time to take another census, said Makra, 48, currently the community trees advocate at the arboretum. Working in close collaboration with the Forest Service, arboretum census takers are counting the trees in the Chicago region this summer. The aim is to get an accurate count of each species living in yards, parkways and parklands in every city, town and unincorporated area of Cook, DuPage, Kane, Kendall, Lake, McHenry and Will counties.
Dubbed Chicago’s “tree czarina” when she worked for Daley, Makra, a certified arborist, received a degree in forestry from the University of Illinois at Urbana-Champaign. She recently spoke with the Tribune about the 2010 census.
Q What is an “urban forest”?
A The urban forest isn’t a place you visit, it is something you wake up in. It is the total tree canopy that covers the urban landscape, city and suburbs.
Q Why do a tree census?
A A very significant portion of the seven-county area is covered by trees. This is our opportunity to understand what that forest looks like. We want to know how many trees there are, what kinds of trees and where they are located. Urban tree canopy coverage is an important measure of quality of life, relating to social, economic and biodiversity benefits.
A Trees provide a number of important ecosystem services, such as improving air quality by removing and storing carbon dioxide, stormwater storage and runoff protection. They provide habitat for many birds, small mammals and insects. They don’t only beautify residential neighborhoods. A well-shaded west wall of a house, where the afternoon sun is the hottest, can save 6.5 to 7 percent of a homeowner’s energy cost to run an air conditioner. The U.S. Forest Service will analyze data we collect and, among other things, put a value on what trees give us in economic benefits.
Q Are your crews going to count and identify every tree in the seven-county region?
A No, they will do their counts within 1,400 random plots throughout the area selected by a computer. Each plot is a one-tenth-acre circle, 74.4 feet in diameter. On a map, it would look like a dot, and they go out and find the plot, wherever it is. The computer site selection is so random that some of them end up in the middle of expressways, where not a single blade of grass grows, let alone a tree.
Q So an expressway plot would be discarded as a part of the census?
A Oh, no. That is part of the picture we are building up, where there are trees and where there are none.
Q What sorts of useful things did you learn in the 1993 tree census covering Chicago and Cook and DuPage counties?
A One interesting surprise that became extremely useful some years later was that 20 percent of the parkway trees were ash. In 2003, when we were confronted with the infestation of the emerald ash borer, we had the opportunity to get out ahead of it a little bit in our emerald ash borer readiness planning. It helps if you see you have a monoculture of trees, like we once did with elms, in planning to avoid disasters like Dutch elm disease.
Q What is the most populous tree in the region?
A That was most alarming. The most common tree was buckthorn, the despised invasive that grows so thickly and pervasively that it is choking out all the native herbaceous and flowering plants of the forest floor wherever it grows.
We were disturbed in 1993 to find that only 3 percent of the trees were native oak, which are so important ecologically. They are the habitat for so many valued birds and insects. We found half of them were very large trees so old that they predate the housing developments they live in. They have been a subject of great passion in the residential teardown trend in which many of the old oaks have been removed. This new census will give us a chance for new analysis.
Q When will the census be completed, and who will use this information when it is released?
A We should be finished with the census by August and expect to have some results from the Forest Service by early next year. We think the information will be very useful for regional planning and for decision-makers at the community level, helping them to recognize that trees contribute heavily to community health. Looking at this regionally is something we can use in outreach and education to influence landowners and homeowners to make good decisions about planting and conserving trees.