[CANUFNET] Canopy Cover

[Julian Dunster]

Since climate change is such a huge issue and its scale is so massive, I
don't think there is anything that we can do at the urban forest level that
will or even can make the sligtest diference globally (the same is true of
trying to promote the UF as a means of effectively sequestering carbon).
This is another issue where we need to define goals first of all. If the
goal is to increase UF canopy in order to help ameleorate summer
temperatures on  buildings, or rainfall pulses, then we have specific and
measurable objectives that we can create and monitor, and very specific
places where such a strategy wil work well. But, setting a goal of 40% cover
is meaningless. Do we want 40% uniformly in the region? (unlikely to be
possible). Is that 40%  at maturity? In perpetuity (whatever that might mean
in a tree context).

How do we know the amount required for a community ?  Is the AF work
scalable between all comunity sizes?  Setting these numerical targets in the
absence of better knowledge and justification is really setting us up for
continued failure because they are virtually imposible to accomplish now or
in the future.

Far better to design, implement and enforce (good luck) design policies
requiring all new developments to plant trees, or engineering departments to
allow more space for trees in road infrastructure etc. But that requirs more
land , and more land may be in conflict with compact community design
principles, densification, infill, or in places like metrro Vancouver, the
requirment for preload materials and new geodetic elevations that anticipate
sea level rise etc. So then we end up using structural soils and tree vaults
in very restricted spaces which also means smaller trees at maturity which
extrapolates to less canopy cover.

And we think there are problems in Canada! I am in Hong Kong right now where
restricted growing space as an issue gets redefined.



-- 
Dr. Julian A. Dunster R.P.F., M.C.I.P., ISA Certified Arborist, ASCA
Registered Consulting Arborist, PNWISA Certified Tree Risk Assessor #1.
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