> in the greater SF East Bay area, likely ranges from 1 colony /2 to 6
acres.
Not all acres are created equal.
> local assoc. focus group to evaluate our KNOWN colony density.
Been there, done that, some of the scars are still faintly visible. :)
I will paste from my notes and contributions below that were for an article
that I cannot find now. (Toni Burnham's article in Bee Culture circa 2013
with a title of something like "Are City Bees Starving?")
First off, just forget about "2 mile foraging radius" and "acres". Both are
very likely overly-optimistic metrics to estimate an urban foraging
scenario, as they are reduced sharply by wind velocities accelerated by
closely-spaced skyscrapers, wind turbulence in the lee of skyscrapers,
rivers that bees refuse to cross, and so on.
Focus on specific local forage plants known to be of value. Gather data
during those blooms.
London promulgated the unfounded fear that urban bees might overwhelm forage
sources. They have a lot of "London Plame trees", which are devoid of any
significant nectar/pollen, yet legislated into being a preferred tree for
London's streets. (They do make fine bee-trees, as they can thrive with
large rotted-out hollows in them.) London had a very high concentration of
beehives in the central core of the city, most put up on roofs by companies
who wanted to seem hip/cool/environmental via "greenwashing". The usual
carpetbagger/profiteer/con artist that appeared in every town with more than
one Starbucks from 2006-2011 was going around selling beehives, and leaving
their owners to figure out that beekeeping was not as simple as it might
have seemed. So they had no significant forage to start, and "hood ornament
hives" made it much worse, as they were unmanaged, or managed by untrained,
un-mentored neophytes.
We had a good number of Plame trees in NYC, but we beekeepers had a good
relationship with the Parks Dept, so we shamelessly lobbied, cajoled, and
arm-twisted the "Million Trees Project" (yes, they did get the number of
trees in NYC up to 1 million) into planting lots of Linden/Basswood, and
other known-excellent bee-forage trees. I am a big fan of Linden, as it
blooms later than most other local forage, and keeps the forging going well
into the late-blooming wild rose bloom. The Parks Dept even has a
work-in-progress map of which trees are where at
http://tree-map.nycgovparks.org (zoom in, and take a look).
Some sites are simply hopeless, most often due to wind turbulence. The more
high buildings, the worse it can be. So, even some green roofs are
¡®solitary/bumble bee only¡¯ sites, or sites where honeybees cannot be
expected to make much of a harvestable crop. I see this here in NYC along
the East River and Hudson Rivers. But most sites even just a block away from
the riverfronts are very productive, as NYC has a good dispersion of large
parks, and most streets are tree-lined on both sides.
Trees swamp out the surface gardens in an urban area. Trees tend towards
spherical and the surface area and volume of a sphere is an easy way to
estimate the equivalent acreage of blooms provided by a tree:
Area = 4 ¦Ğ r2
Volume = 4/3 ¦Ğ r3
Bloom density = Pick a number, say 2 inches from each other in all
directions
Below is a *.csv chart you can paste into a spreadsheet of the equivalent
"acres of blooms", but a single tree with a foliage radius of 20 feet is
equal to 0.12 acres of blooms if the blooms are only on the surface, and 4.6
acres of blooms if they are evenly dispersed within the "sphere" of foliage.
=-=-=-=-=-=-=
Tree Foliage Radius
(feet),5,10,15,20,25,30
=====================
Surface Area (sq ft),314 ,1256,2827,5026,7853,11309
Volume (cubic feet),523,4188,14137,33510,65449,113097
Surface Equivalent acres,0.01,0.03,0.06 ,0.12,0.18,0.26
Volume Equivalent acres,0.07,0.58,1.95,4.62,9.02,15.58
=-=-=-=-=-=-=
According to a 2010 compilation of data on urban tree coverage by NYC
Department of Parks, the average tree canopy in American cities covers 27%
of the land (Atlanta comes in first at 36.7%, NYC was only 24% in 2010).
One can also survey the hives themselves in two ways, "lavender bee
magnets", and hive weighing (Shameless plug for http://Nectar-Detector.com
goes here).
The lavender magnets are easy, but labor-intensive - get some potted
lavender at a greenhouse in spring, and toss it in cold storage until your
local dearth. Mark bees that arrive, asking members to check their own
hives that day to see if marked bees return from foraging. You may not have
the maximum travel distance, but you'll have a good idea. We found that
bees will not cross the East River or Hudson River at all, but foraging bees
from under the Brooklyn Bridge will consistently fly all the way to the Red
Hook area of Brooklyn to gather significant nectar, a straight-line distance
of 2.75 miles.
Weighing hives is less labor-intensive, and lets you quickly quantify which
hives at which sites are bringing home more nectar, and the results are
often counterintuitive. "Right next door" does not mean similar results,
even over several stubborn years of persistence by the beekeeper with a hive
in a "poor" site.
The good news is that urban hive densities are way down across the board all
the hype over keeping bees has subsided, and the hipsters have moved on to
less demanding hobbies, like macram¨¦ and craft beer brewing. Good
riddance. I was once again able to implement our cooperative spring package
pickup with a single Volvo wagon this spring, mostly because everyone has
learned to requeen and make splits in the fall, some the hard way.
Suburbia? The same rules apply, but with less wind turbulence, as there is
little of suburbia that is not impacted by the Chem-Lawn man, who is truly
the enemy of beekeepers. The putting-green lawns might as well be asphalt
and concrete for all the value they provide to bees, and little
postage-stamp sized flower gardens won't help much. Worse yet, grandma
Jones has trouble reading fine print, even with her bi-focals, so she will
do a ground drench on her prized late-blooming roses with pure undiluted
100% imidacloprid concentrate, rather than diluting the concentrate per the
label instructions. This will cause a bee-kill that will panic the entire
association.
Rural Ag land? Feast or famine, depending on what is grown, and when it
blooms. Oh, yeah - don't forget that poison will be sprayed during the
growing season, and "poison" in the context of bees now rightly includes
many herbicides, not just many pesticides.
I can't be the only guy with data. Anyone else?
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