:: Critiques ::

UFORE and CITYgreen have limitations and even methodological problems that users and others should be aware of. The following is a summary of some of these issues and findings, divided into two categories: issues related to use and issues inherent to the software.

User Issues

-- Data Uncertainty: While there is some uncertainty associated with the model calculations, even if they work perfectly, they are only as good as the data that is input. Thus, it is crucial that user are not only as accurate as possible, but also that they are aware of the potential for error in sampling and measurement.

-- User Ignorance: Lay users may not be aware of 'problems' with the software itself and develop inaccurate analyses. For example, Longcore et al (2004) found that in CITYgreen 4.0, a runoff analysis could be run without clipping landcover layers so that they did not overlap (failure to do this would result in incorrect outputs). Users who were not aware of this conflict would have run the model incorrectly, yielding bad estimates.

Software/Model Issues

-- UFORE Inaccessibility: UFORE is currently a rather inaccessible application, both because of its SAS platform as well as the fact that users cannot work independently of the NFS. However, the developers are addressing this and appear to be headed in a direction of increased accessibility and user-friendliness

-- Air Pollution Nearest City Calculations: Air pollution calculations rely on extrapolating data from the closest studied city or a representative studied city. In CITYgreen 5.0, there are only 10 such cities to choose from. UFORE also has a limited number. These are unlikely to be good estimates for many areas, particularly those outside the U.S.

--CITYgreen Energy Calculations : A study by Carver et al (2004) tested the energy savers module of CITYgreen and found that while it performed well for a highly vegetated, older area, it performed poorly for . While it remains unclear why this is the case, it may be a fault of underlying assumptions and extrapolations.

--Science Limitations:These models are not completely at fault for some of their limitations. The need to extrapolate from other cities, for example, or the ability to calculate energy savings only for 1-2 story houses is not the fault of the models, but suggest a need for more development of the related research.

-- Longcore et al (2004) Critiques: In one of the most significant reviews of CITYgreen (v 4.0), Longcore et al 2004 has noted that in order for CITYgreen to influence policy its scientific foundations must be "sound" and is conversion to economic terms must be "reasonable". They studied the former and noted the following problems (most of which have not been dealt with in v 5.0):

• Canopy coverage is used as a proxy for leaf area, while ignoring canopy height/diameter
• Estimates for carbon storage based on stand age can result in impossible values (for example, when young trees are added and shift the overall age distribution, carbon storage can decrease)
• Runoff calculations do not consider spatial variability and assume all surface connect to drains
• Poor estimates for soil conditions can have enormous impacts on results
• Economic estimates need to be flexible for different local conditions

-- Carbon Sequestration and Tree Maintenance: Although both models calculate carbon storage and sequestration, recent studies by the FS suggest that tree maintenance CO2 costs may actually exceed tree sequestration benefits. This issue also returns to the above point about user ignorance; failing to understand or consider nuances of the science and issues has the potential to be problematic.

Other

-- Need for Review: In general there appears to be a dearth of good independent analysis of the software. Work by Longcore et al (2004) and Carver et al (2004) provide valuable insight into the workings of the software. This type of review serves to improve the models, the analyses, and the many arguments and plans that rely on them.