Heritage Tree Ordinance Part 1

6CO2+5H2O = C6H10O5 + 6O2

Trees take in carbon dioxide and water, both things we have too much of here in DG, fix the carbon to the water to make…more tree (cellulose), and exhale the remaining oxygen. Most trees have root structures that are wide and shallow to gather nutrients and water, and maybe some soil based carbon. A fully grown tree can absorb up to 600 gallons of water in a 24 hour period. Once the soil surrounding a root structure has been flooded or saturated, that ability is greatly diminished; that is why many trees die if their surroundings get too wet.

Some trees, like swamp oaks, red maples, river birches, keep soaking up water whether or not the ground is saturated. They adapted to the marshy lowland prairies where we now live. Willows are the midwest champs for soaking up water, but they grow fast and are weak, and tend to fall over in high winds.

Shade trees have expansive canopies for several reasons; to collect gaseous carbon dioxide (greenhouse gas), to collect sunlight as the trees’ power source for the chemical reactions, and to transpire out the oxygen and excess water vapor.

Oak, maple, hickory, can get very big and live a long time. There are many in Downers Grove over 100 years old, very large, usually over two feet in diameter at chest height (Diameter Breast Height, or DBH). They do a lot for us besides keep us in shape picking up fallen sticks and branches every spring and raking leaves every fall, and providing homes for birds and squirrels and other wildlife. When Pierce Downer moved here, he set up his homestead near a grove of trees. No trees, no Pierce Downer, no Downers Grove.

By blocking direct sunlight and transpiring water vapor into the air, trees provide a cooler shaded area. A big enough tree shades one or more homes, effectively reducing energy costs to cool a home in summer. They act as wind breaks, reducing energy costs of heating in winter. They soak up water, reducing the effect of heavy rains. They slow the movement of water run off. They clean up water by acting as a natural filter. They exhale oxygen into the air. In a village with stormwater problems that cost many millions to fix, and in a world obsessed with global warming and greenhouse gases, that matters.

In 2005, the village enacted specific measures to protect public and parkway trees. Proposed by the Village Forester, it was a direct response to development killing trees, primarily by damaging the root structure and the tree trunk. Before, trees were in the way; now, trees must be protected to their drip line with a chain link fence, and no materials or vehicles can damage them.

At that time, the Village Forester also proposed similar protections for “heritage” trees on private property that were deferred for future consideration. In a few weeks staff will bring council a “heritage” tree ordinance that will effect large, mature trees of a specific type, size and age. Last time, two years ago, the proposal was fairly extensive and ambitious.

Most communities use a tree preservation ordinance as a tool when working with developers. Rules and requirements are clearly set down in writing so there is no misunderstanding of the expectation and intention to preserve large “heritage” trees. Builders in communities that have such an ordinance cannot simply clear cut properties and then design a project. Instead, there is a survey of trees on the property, and, in meetings with staff, decisions are made regarding what happens to the “heritage” trees.

What matters is trees help us and contribute to the desirability, the livability, of the village as a whole. We will lose our ash trees to the Emerald Ash Borer: a certainty that is no longer a discussion topic for all but the most grossly uninformed. That 18.6% of our public tree canopy goes away is not trivial; ash trees are efficient helpers that will not be replaced for many years. We have no more margin for error. We need all of our trees, or as many as we can keep to help our village through the next 40 years: not just trees on public land, all trees.

There has been significant talk by residents about what such an ordinance should and should not do; whether it is needed or not. Everyone likes trees, but a tree ordinance that crosses over to private property collides with personal property rights. No one wants government interfering with their personal lives, wants being told what they can and cannot do on their own property.

When the village publishes the green sheet information on February 22 we should have a better idea of the scope and purpose of the proposed ordinance.


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