<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Hi Darren,<div class=""><br class=""></div><div class="">Here is Portland, OR and their 2007, <u class="">Urban Forest Canopy Report</u>.</div><div class="">You may find the Executive Summary of interest, as well as <i class="">The Benefits of Trees (</i>pages 27 to 30), and the Appendix A. Curiously - I did not know this - the Sweet Gum (<i class="">Liquid Gum</i>) produces high amounts of biogenic volatile organic compounds (BVOCs), which adversely affects their net contribution to air quality. I knew that those colourful fall leaves of the Sweet Gum had to have some trade off cost. Nonetheless, Sweet Gum do rank high for Energy conservation, CO2 absorption, Stormwater management, and of course, Aesthetics, which are comparable to Birch and Maple for those fall colours. Sadly, the great Elm is a very highly ranked for their environmental </div><div class="">contribution to the city’s “green assists.” Hope that helps.</div><div class=""><br class=""></div><div class="">Best,</div><div class=""><br class=""></div><div class="">John Martyn, Consulting Arborist</div><div class="">JPM Tree Service</div><div class="">Since 1996</div><div class="">Coquitlam, BC</div><div class="">604.789.4045</div><div class=""><br class=""></div><div class=""></div></body></html>