Subject: [Tweeters] introduced species
Date: Sep 7 23:54:34 2005
From: Allyn Weaks - allyn. at tardigrade.net


On 6/9/2005, sgmlod at aol.com wrote:

But back to the thorns. I do take exception with the venom some direct
at certain species like blackberries. Our various introduced species
provide incredible wildlife habitat for a variety of native species in
our highly (and irreversibly) altered suburban landscape. When removed,
they are not replaced with native blackberries (or if such happens, it
has not been in my stomping grounds) and they are typically replaced by
native species with far less wildlife value or "whatever" is allowed to
grow back in their place. In wild areas, I could understand their
removal. In Seattle or Everett, removing them because they are not
native seems like folly.

Bryan LaComa already sent a good answer. But even so I'll subject
y'all to most of a post I wrote up awhile go on pnw-natives. I'd
likely do it differently if I did it over, but recycling conserves
energy :-)

================
At 8.17 pm -0800 13/12/97, Birkeland quotes from the Newsletter of the
Burke Mountain Naturalists:

[snip, and quotes are out of order...]

>I'm not saying that blackberries should not (in some places) be managed in
>environmentally friendly ways; but wholesale destruction of bramble hedges
>is fundamentally wrong.

Well, it's a complex subject, so one really needs to make complex
observations. Noticing that:

>if one
>were to rate all plants, both native and naturalized, the bramble would
>come out near or even at the top, as one of our best wildlife plants.
>Birdwatchers know very well that the places for observing wintering
>sparrows (including the rare species) is in the bramble bushes.

is not enough. You have to look at all species and over long times.

Wildlife isn't just birds and mammals and adult butterflies, it's the
fish and invertebrates in nearby waterways, the insects that live on
the plants, the spiders that eat the insects, the decomposers which
live in the soil and keep the whole shebang going. It generally isn't
the number of birds you see that matters, but the number of species and
which species. I have zillions of birds in my neighborhood: starlings,
crows, house sparrows, house finches, pigeons, bushtits, chickadees and
robins. All the usual city slickers. All are good generalists, and
can cope well with almost whatever they find; if they specialize in
anything, it's in living off of human disturbance. Those which would
be native here, such as the crows and chickadees, are probably here in
much higher densities than they would be if Europeans had stayed at
home. But what I _don't_ often see in my neighborhood is more
important--the many, many species which don't specialize in human
disturbance. Warblers, woodpeckers, kingfishers, owls, etc. would all
have been here before Piper's Creek was turned into part of a storm
drain, but they aren't here now. They aren't in that blackberry patch,
either, unless the patch adjoins better habitat. Quite likely those
other species would not have been here in large numbers per acre. But
quality beats out quantity, and for ecosystems, quality is more likely
to be measured by number of species than by number of individuals. In
that number of species, you also have to include the number of insects,
spiders, and all. The more species, the better the long-term stability.

It's very easy to concentrate on the creatures that pop out at you,
such as bears, birds and other warm fuzzies. But in the scheme of
ecosystems, these easily noticed critters are often the least important
part. The system is kept running by plants, along with fungi, insects,
bacteria and other low-lifes. If we take care of _them_, they will
automatically take care of all those warm fuzzies. If we only take
notice and care of warm fuzzies, we could easily lose everything.

So take another look at that blackberry patch, especially if it's a big
one, and at least somewhat isolated from native habitat. The number of
fruit eating and wintering birds may go down if you replace the
blackberries with native plants (especially if it's replaced with a
native monoculture), but I bet that if you look more closely and count
all 12 months rather than just in fruiting and wintering seasons, the
overall number of species will go up once new native plants are well
established (especially if they've been well chosen). Those native
plants can support far more insect life, and more species of birds need
insects than need fruit, especially while raising young. For
overwintering shelter, well, blackberry is thornier than most native
thickets, and may protect some birds better from predators. This would
be ok if the only predators to be considered are non-native house cats.
But weasels, bobcats, and hawks are wildlife too, and they deserve a
fair shot at a january dinner :-) And keep in mind that those
overwintering sparrows are mostly going elsewhere to eat.

In the short term, snowberry may be less desirable to fruit-eating
birds. But this means that in a particularly bad winter, it will still
_be_ there as a starvation food long after the more desirable foods
have disappeared. The article admits this: ("Shrubs such as snowberry
(waxberry) with its white fruit, go largely ignored by most birds,
unless winter conditions are extreme") but without following the
thought through to the consequences. Too much of a good thing can keep
a population higher than is justified for a while, but if it's the only
food there is, that population will be in for a spectacular crash when
conditions aren't great.

In the long term, think succession--once blackberry takes over an area,
it's darned hard for anything else to get a toehold. Blackberry is
unfairly hard to compete with because it _doesn't_ support the myriad
of insect wildlife and diseases which tend to keep native shrubs in
bounds, allowing the next generation of species to come up and
eventually change the landscape again--shrubs, to alder, to hemlock.

The lack of insect control means that blackberry grows in strong
monocultures. Native plants grow in communities, and short term
monocultures that might sprout up after fire or such usually give way
pretty quickly to variety. Microclimates can vary from foot to foot
and even inch to inch, and specialist natives can take good advantage
of this. The increased plant variety means increased food variety
(fruits, small seeds, nuts, many many species of insects and other
invertebrates) which can allow an increased bird and mammal variety.
Not necessarily increased numbers--wild areas and wildlife gardens
aren't, and shouldn't be, zoos. More biomass at the top of the pyramid
isn't better if you want a self-sufficient system with no extra food
being trucked in from the midwest...

There are several books that I would love to make required reading for
all humans. One of them is Edward O. Wilson's _The Diversity of Life_.
Not only is it full of good ecological information and rules of thumb,
but it's outstandingly well written as a bonus. So don't take my word
for anything (I'm only an amateur, after all). Read Wilson, an
entomologist/ecologist who has been instrumental in making
'biodiversity' a major current emphasis in ecology.

Then kill off that blackberry and replace it with a variety of natives :-)
--
Allyn Weaks allyn at tardigrade.net Seattle, WA Sunset zone 5
Pacific NW Native Wildlife Gardening: http://www.tardigrade.org/natives/
"A proud member of the Reality-Based Community"