[CANUFNET] tree canopy target

Wed Jun 22 14:38:39 EDT 2016

Vraiment intéressant!  Personne n'a mentionné l'évapotranspiration , donc
l'eau disponible pour les racines.
S'il s' agit de rafraîchir l'air dans les vagues de chaleur, il est au
moins aussi important de voir à ce que les arbres aient de l'eau en
abondance.
Je pourrais essayer de traduire en anglais,  mais je ne suis pas un bon
traducteur!

Louis-Marie Poissant
Le 2016-06-22 14:22, "Louis-Marie Poissant" <lmpoissant at gmail.com> a écrit :

> Merci! Je n'avais jamais vu ce document!
> " Le couvert forestier devrait représenter au moins 30 % du bassin
> hydrographique. C'est une approche très risquée permettant d'abriter
> seulement moins de la moitié de la richesse potentielle des espèces et des
> systèmes aquatiques à peine viables;"
>
> Louis-Marie Poissant
> Le 2016-06-22 13:01, "Margot Ursic" <mursic at beaconenviro.com> a écrit :
>
>> Another source of the "40% urban forest cover target" that is sometimes
>> cited in eastern Canada is Environment Canada's How Much Habitat is Enough?
>> Guidelines, last revised in 2013.
>>
>> These guidelines put forward 30% forest cover at the watershed scale as a
>> generalized minimum to sustain certain ecological functions (described as
>> "high-risk"), 40% as a "medium-risk" level, and 50% as a "low-risk" level
>> for sustaining potential species and healthy aquatic systems in a given
>> watershed. These guidelines are intended for the Mixedwoods Plains zone,
>> and while they are science based, the document acknowledges that there are
>> many gaps in the available science on this topic.
>>
>> These guidelines also notably apply to natural or semi-natural forest
>> cover, so would exclude canopy from street trees and the like.
>>
>>
>> Margot Ursic, M.Sc. / Planning Ecologist, Facilitator
>> BEACON ENVIRONMENTAL
>> 373 Woolwich Street, Guelph, ON  N1H 3W4
>> T) 519.826.0419 x21  F) 519.826.9306  C) 519.803.8101
>> www.beaconenviro.com
>>
>>
>> -----Original Message-----
>> From: CANUFNET [mailto:canufnet-bounces at list.web.net] On Behalf Of Brian
>> Geerts
>> Sent: Wednesday, June 22, 2016 10:28 AM
>> To: 'Canadian Urban Forest Network' <canufnet at list.web.net>
>> Subject: Re: [CANUFNET] tree canopy target
>>
>> ‎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/>
>> [UFI new logo very small]
>>
>>
>>
>>
>> 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/>
>>
>> Vision: To be the most livable town in Canada Please consider the
>> environment before printing this email.
>> http://www.oakville.ca/privacy.html
>> 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>
>>
>>
>>
>>
>> This communication is confidential and may contain information protected
>> by Privacy legislation.  Unauthorized use is strictly prohibited.  If you
>> are not the intended recipient or have received this communication in
>> error, please notify the sender immediately by telephone.
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://list.web.net/pipermail/canufnet/attachments/20160622/fbda9aaf/attachment-0001.html>