Riverwoods Preservation Council

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Bluebirds Ho Min Lim

Woodland Health Study

November / December, 2009




(Photograph by Ho Min Lim)


The RPC recently completed a woodland health study of sample sites in Riverwoods, using outside experts. The study is the first step in answering the basic question: What is the condition and future of our woodlands?

What Did the Study Show?
The Riverwoods Preservation Council (RPC) recently completed a woodland health study of sample sites in Riverwoods, using outside experts. The study is the first step in answering the basic question: What is the condition and future of our woodlands? 
It’s important to keep in mind that a “woodland” is not just trees.  A healthy woodland consists of four layers:  large trees (the canopy), a lower layer of trees (the subcanopy), shrubs and understory plants.  Variety and abundance are keys.  Among other findings, the study concluded that most oaks in Riverwoods are mature.  Young oaks and oak saplings are conspicuously absent.  If this situation continues, oak trees will disappear from our woodlands.  Overall shrub abundance and variety were low in every sample plot.  The likely causes are deer browse and shading from the tree canopy.  Further, there is a high percentage of bare ground within the understory layer of each plot.  Low plant abundance and variety, a high percentage of bare ground and high shade levels all indicate poor woodland health. 

Nature is Out of Balance
Our presence has disturbed the natural balance.  We’ve eliminated natural deer predators, imported invasive plants and insects, and prevented the periodic fires that helped regenerate oaks.  But the reality is that we all love Riverwoods, and we don’t want to leave.  So the next best thing is to reduce the adverse impacts of our presence.

Isn’t the Woodland Protection Ordinance Enough?
In 2005, the Village Board of Trustees adopted a Woodland Protection Ordinance to reduce the further loss and fragmentation of woodland areas.  The Board stated the benefits of a healthy woodland:  reduction of stormwater runoff; lessened severity of local flooding; shade and cooling; erosion control; filtering of water pollutants; recharging of aquifers for drinking water; replenishment of the groundwater table; maintenance of water flow; cleansing of the air; mitigation of global warming by absorbing greenhouse gases; promotion of a biologically diverse community of micro-organisms, plants and animals; and promotion of higher property values for woodland areas in the Village.
The Woodland Protection Ordinance is a very sound policy.  But it’s an incomplete answer, since the Village Board necessarily tried to minimize regulatory interference with residents’ use of their properties.  Many Riverwoods residents, in managing their own properties, have gone beyond the limited requirements of the Woodland Protection Ordinance.  They sought to do more.  They see themselves as stewards of the woodlands, and look beyond their own inhabitance of the properties.  They feel that they are rehabilitating the woodlands for the benefit of the community and future generations.

RPC’s Recommendations to the Board
Based on the Woodland Health Study and review of scientific literature, RPC proposed a number of management practices to the Village Board of Trustees on October 20.  Included in RPC’s recommendations were control of deer populations to allow shrub and understory plants to mature and to allow oaks to regenerate; manual thinning of shrubs and small trees to allow more light to the understory;  use of a consultant ecologist (in addition to the Village forester) to assist with woodland rehabilitation programs; implementation of carefully prescribed burns to prevent invasive shrubs while maintaining native shrubs, understory plants and oak saplings; and creation of more user-friendly versions of the Village’s reforestation and invasives removal programs.  RPC has offered to participate actively with the Village to help develop a comprehensive woodland stewardship plan.

Giant Tree HowieRiverwoods Tree Count
The RPC has created a program to count the larger trees in the Village.  The purpose of the program is to determine to what extent a mature forest exists in Riverwoods.  Trees with 2 foot or greater diameter will be located, measured and identified, and the ten largest trees will be reported.  Acorns and seeds from the largest trees will be collected and planted, to help grow the next generation of oaks.

The tree count is in process.  We may already have found one of the largest trees in the Village.  The tree, a Swamp White Oak, is 4 feet 7 inches in diameter and is located near the Des Plaines River on the Patterson Nature Preserve.  We estimate that the tree is 166 years old.  [An image of the ancient tree is shown here, with Howie Patterson standing in front for perspective.]

Beginning in March 2010, RPC will need six additional volunteers to complete the tree count.  If you are interested in helping with this program, please call Howie Patterson at 945-9281.

© Riverwoods Preservation Council- - Page last updated: December 2009