[CANUFNET] tree canopy target

Wed Jun 22 10:27:31 EDT 2016

‎I believe the 40% number came from  studies of the Chesapeake Bay area geared towards watershed water quality - from "Urban Tree Canopy Goal Setting: A Guide for Chesapeake Bay Communities"

Brian Geerts
Manager of Forestry and Horticulture
City of Cambridge
Dickson Centre
30 Parkhill Road W. ON N1R 5W8

geertsb at cambridge.ca

Tel:519.740.4681 x4558
Fax: 519.624.6975

From: Alex Satel
Sent: Wednesday, June 22, 2016 10:20
To: 'Canadian Urban Forest Network'
Reply To: Canadian Urban Forest Network
Subject: Re: [CANUFNET] tree canopy target

Hi Alan (and all),

I think the very fact that we aren’t able to jump forward with a quick reference to why 30% is “good” but, say, 25% isn’t, supports what Dr. Duinker has already said – these targets are rarely based on science or even high-level assessments of what is possible or reasonable.

The 40% canopy cover target that’s been adopted by many communities seems to go back to a publication by American Forests, which set that level as “optimal” for US cities east of the Mississippi. I can’t dig up the publication as the link I had to it on AF’s website is broken. That same publication set lower targets for western regions (somewhere in the order of 20-30%, I believe). I honestly can’t recall the basis behind those figures.

It seems that urban forest managers and decision makers have decided to run with targets within that range for any number of reasons, not the least of which is that they probably just ‘seem’ reasonable and achievable. I think a lot of it also has to do with what Dr. Duinker said – peer behaviour. Communities are constantly benchmarking against each other – it wouldn’t look good for community X to set a target of 24% if neighbouring community Y has a target of 35%, even if community X had done an exhaustive potential canopy cover study and found 24% to be a realistic target based on its potential carrying capacity. I’ve even heard of one community that set its target because “30 by 2030” (or was it 40 by 2040? I can’t recall) had a nice ring to it and was sellable.

Your question again raises valid issues with these high-level canopy cover targets:

·         are they achievable (how much canopy can we actually cram into this urban area)?

·         Would they actually translate to tangible increases in benefits (and therefore, should we even be trying to achieve them)?

·         When we say 30% or 40%, what do we really mean (is that 30% averaged across the entire area, where forest stands can be 95% canopy but neighbourhoods where people actually live only 10%)?

·         Does focusing on increasing canopy detract resources and attention from other important urban forest management activities (risk management, protecting existing trees, etc. etc.)?

·         and on and on…

Cheers,

Alex

Alex Satel, MFC
ISA Certified Arborist ON-1353A
Urban Forest Innovations, Inc.
1248 Minnewaska Trail
Mississauga, ON L5G 3S5
P: (905) 274-1022
asatel at ufis.ca<mailto:asatel at ufis.ca>
urbanforestinnovations.com<http://www.urbanforestinnovations.com/>
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From: CANUFNET [mailto:canufnet-bounces at list.web.net] On Behalf Of Andres Olaya
Sent: June-22-16 8:00 AM
To: Canadian Urban Forest Network
Subject: Re: [CANUFNET] tree canopy target

Good morning colleges:
I’ve found this interesting article (World Health Organization web site) that might give us some answers:

http://apps.who.int/iris/bitstream/10665/174012/1/9789241508537_eng.pdf?ua=1

Have a great day.

Andres Olaya
Forestry Information Analyst, Central Operations
Parks & Open Space
Town of Oakville | 905-845-6601, ext.2900 | www.oakville.ca<http://www.oakville.ca/>

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From: CANUFNET [mailto:canufnet-bounces at list.web.net] On Behalf Of Peter Duinker
Sent: Tuesday, June 21, 2016 2:05 PM
To: Canadian Urban Forest Network
Subject: Re: [CANUFNET] tree canopy target

Greetings Alan:

Canopy targets for a city or town are, in my view, fairly arbitrary and definitely not generalizable.  I hold the view that targets are never scientifically based because they depend on people to express preferences and are therefore value-based.  The target-setting exercise can be scientifically informed, of course.  In the case of urban-forest canopy, one might expect an analysis of current canopy coverage and its benefits, as well as a range of forecasts detailing how many more trees it would take to get to a specific canopy coverage, and what would be the benefit stream associated with each scenario of canopy coverage.  I have never seen this done.

One could look at the question this way: what factors influence the setting of a canopy target?  Factors might include: (a) the current canopy, which is presumably lower than the target; (b) the cost, in terms of new trees established, to get to a specific canopy target at a particular future year; (c) the prospects that the cost predicted can be covered from the various budgets available; (d) the increase in benefits associated with the targeted canopy cover; and (e) what other cities and towns are doing in this respect.  While (a) through (d) are sensible factors, (e) is less so, but I’ll bet that many urban-forest strategies are based on peer behaviour when it comes to canopy targets.  Perhaps it boils down to this: how much canopy cover would we ideally want?  Probably much, much more than we have today.  But how much canopy cover can we realistically hope to achieve in the next decades?  Probably some smallish fraction of the ideal.  So let’s pick a number that seems achievable and gets us substantially more canopy than we have today.

I would be most interested to know if anyone is using a more sophisticated approach than this.

Best wishes, Peter Duinker

Peter N. Duinker, PhD, P.Ag.
Professor
School for Resource and Environmental Studies
Faculty of Management
Dalhousie University
6100 University Ave.
Halifax, Nova Scotia, Canada
B3H 4R2
Phone: 902-494-7100
Cell: 902-229-5141
Fax: 902-494-3728
Email: peter.duinker at dal.ca<mailto:peter.duinker at dal.ca>
http://www.dal.ca/faculty/management/sres/faculty-staff/our-faculty/peter-duinker.html

From: CANUFNET [mailto:canufnet-bounces at list.web.net] On Behalf Of Alan Kemp
Sent: June 21, 2016 1:11 PM
To: 'Canadian Urban Forest Network' <canufnet at list.web.net<mailto:canufnet at list.web.net>>
Subject: [CANUFNET] tree canopy target

The City of Nanaimo has an Urban Forest Management Strategy. In that Strategy we have a target of increasing our forest canopy to over 30% in the next decade. Of course this is difficult in the urban setting. Our Management and Protection of Trees Bylaw supports this document by requiring tree replacement plans for development, which in general terms works. However, I was asked why 30% or even 35%? What is the scientific reasoning behind that. Although I can explain all the benefits of an urban forest, I could not really give a good science based answer. I have looked through a lot of literature, but don’t seem to be able to give a reasonable answer.

Any suggestions?

Alan Kemp
Urban Forestry Coordinator
Certified Arborist, Certified Tree Risk Assessor
Community Development
City of Nanaimo
250 755 4460 (local 4357)
alan.kemp at nanaimo.ca<mailto:alan.kemp at nanaimo.ca>
www.nanaimo.ca/goto/urbantrees<http://www.nanaimo.ca/goto/urbantrees>

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