How to PreserveTrees During Construction
Why is this topic important?
What harm can construction cause?
- The urban forest makes city living healthier and
- it removes the greenhouse gas carbon dioxide from the
- it cleanses the air of a range of pollutants
- it moderates air temperature , reducing air conditioning
and heating energy use
- it increases property and commercial values
- it instills a sense of well-being and connects people to
- Large healthy trees carry out these functions particulary well,
but are often the most sensitive to construction damage and can not be
quickly or easily replaced.
- Development and construction constitute the most serious threat
to these benefits of the urban forest.
How can preservation be done?
- The worst damage occurs underground, where it is invisible
until its aboveground effects become apparent.
- Underground damage includes:
- compacting the soil so roots cannot breathe and water cannot
- killing roots and soil organisms through dumping or spilling
- severing roots, especially those greater than about 1" in diameter,
compromising tree health and stability
- Although more obvious, aboveground damage is usually only serious
when it affects large trunk areas or large branches.
- Be proactive. Don't wait until construction
starts to start taking steps to preserve trees. It is much easier
to prevent damage than to correct it.
- Recognize that both construction and preservation need
space. These competing demands need to be resolved as fairly as possible,
usually in.collaboration with a project's architects, engineers, and/or builders.
- Establish a root protection zone with strong fencing placed
a correct distance from the trunk. The distance varies by species
and soil, but out to a tree's dripline is a minimum, with greater distances
for narrow crowns or sensitive species like sugar maple.
- Use formal agreements with strong penalties attached.
This is the best approach for individuals as well as for communties.
White oak that later died for lack of root
protection during construction
Which trees should you preserve?
Where can I get more information?
- There is little point in putting in time, cost and effort
into preserving a tree in poor condition.
- An evaluation of the trees on a potential construction site is
recommended, with the following considerations:
- The tree's crown should have the density, color, and foliage
normal for its species and age.
- The tree should be mechanically stable, and not pose a serious
risk to forseeable targets.
- Avoid preserving species that are unsuitable for the site. Important
factors to consider include:
- growth rate
- pest susceptibility
- Since health, stability, and suitability are
not obvious traits, you will usually need a professional for this task.
- Matheny, Nelda, and James Clark. 1998. Trees and
development. A Technical guide to preservation of trees during
land development. Champaign, IL: ISA.
For other information, advice and help on this topic, call offices
of your State Urban Forestry Coordinator or University Extension service,
or visit urban forestry web sites.