Subject: Re: invasive vines and habitat
Date: Dec 7 21:16:44 1998
From: Michael Price - mprice at mindlink.bc.ca


Hi Tweets,

Katie Sauter writes:

>On a CBC scouting mission on Queen Anne Hill yesterday morning I for the
>first time took a good look at the ravine on the NE side of the hill (from
>the bridge on McGraw St.) and was horrified by the degree to which the
>ravine has been taken over by invasive vines.

>My questions are these -- obviously this unusual plant community is
>currently supporting a moderate number of winter city birds, but left to
>itself, will these vines kill everything on which they climb?

Yes. There is an increasing number of smothered and strangled dead and dying
large trees in Vancouver BC, where (mostly) out-of-control ivy and other
vines are the groundcover and tree-girdlers in many parks (including much of
the once-wild areas of Stanley Park and, increasingly, Pacific Spirit Park
and the University Endowment Lands).

>Once the
>shrubs and even trees have been completely eliminated, will bird species
>diversity decline?

I don't know, but what are the tree-nesters going to do when the trees are
dead and the foliage gone?

>Which species can use these vine mats, or even prefer
>them?

Two that I've seen: in urban areas, House Sparrow Passer domesticus, as a
roost/social habitat (make it three--sometimes House Finch Carpodacus
mexicanus, as a roost/social area, but not to the degree of the former); in
the 'wild', Winter Wren Troglodytes troglodytes, as a forage habitat.

>I've been involved in a fair number of efforts to remove invasives from
>various public places and to plant natives, so I know the ultimate futility
>of the exercise (not that it isn't incredibly satisfying on a small scale!)

What a depressing little paragraph given how much degradation and
destruction of wildife and habitat I've witnessed in Vancouver BC over the
last several years here. Often it's the Vancouver Park Board itself which
introduces the invaders to the wild ecosystems and the local nature
organisations which are cognisant of the problem don't seem inclined to make
an issue of it.

>Given that invasives are here to stay, what level of habitat are they
providing?

Less than what was here, probably, until or unless a native species can
adapt sufficiently to eat it or use it somehow. I think Butterfly Bush
(Buddleia sp.?) has been one of the few introduced species which has paid
its way with value to the local ecosystems, judging by the large numbers of
moths, butterflies, bees and hummingbirds go to work on the 'bottle-brush'
flowerheads.

Michael Price
Vancouver BC Canada
mprice at mindlink.net

"She's psychic....we've decided to find it charming."
--Frasier