We were interested in finding a method to look at the campus urban forest from a more holistic approach. The method chosen to acheive this, was the concept of "ecological integrity".
There are several differences of opinion surrounding the concept of ecological integrity (Francis et al., 1993), some definitions include:
National Parks define their goal of ecological integrity (CCIW, 1995):
A condition where the structure and function of an ecosystem is unimpaired by stresses induced by human activity are likely to persist.
Aldo Leopold defines a more ethical basis for ecological integrity:
A thing is right when it tends to preserve the integrity, stability and beauty of the biotic community. It is wrong when it tends otherwise(Francis et al., 1993).
While both definitions adequately define the concept of integrity, we felt Kay (1989) provides the definition most applicable to the management of UWs urban forest:
If a system is able to mainain its rganization in the face of changing environmental conditions, it is then said to have integrity.
In using the concept of ecological integrity, we are not suggesting that Plant Operations attempt to recreate "pristine conditions". Instead we suggest that management strategies repair ecological systems by restoring essential ecological functions, promoting long-term stability (Haugh et al., 1997).
To measure ecological integrity, standards or norms for quantitative indicators must be determined (Francis et al., 1993). For the purposes of maintaining integrity on the UW campus, we have chosen to use the following aspects as indicators of integrity:
When selecting trees, consider the following aspects:
The UW campus currently has a diverse tree community, that varies in in size, colour and flowers.
It is important to consider the adaptability of plant species to the UW campus environment. The ability for plant species to establish and become aesthetically pleasing, depends on the plants tolerance to environmental conditions (Hitchmough, 1994). In ascertaining the suitability of the site, characteristics such as moisture, soil type, and sunlight should be considered, and be suitable to plant type (Hitchmough, 1994).
Increasing species diversity of our urban forests is important to their long-term ecological stability....Four types of diversity should be considered, two are above the species level (structural and functional diversity) and two are below the species level (life-cycle and genetic diversity).
Although opinions vary as to whether diversity should be an indicator of integrity, we feel that a diverse ecological landscape is beneficial to the UW environment.
It is also important to consider the ecological functions that the urban forest provides as a whole. Previously in this report, each of these have been discussed. It was felt that it in order to work toward ecological integrity, the UW urban forest should provide the following functions: microclimates, wildlife habitat, prevention of soil erosion, and reduction of airbourne environmental pollutants.
When it became a matter of quantifying "forest decline", scientists and forests faced a major difficulty: There was no universally acknowledged health indicator.
In completing the tree inventory, we have done a visual assessment of the health of trees on campus. Some criteria used in the tree inventory to assess health included:
By monitoring the UW urban forest for these indicators, management strategies can be oriented to working toward ecological integrity.
Another indicator for determining health in the future would be to note any occurances of premature leaf fall.