The Preachy Blog
5/9/2009 -- Backyard Biodiversity
Topic of this year's Biodiversity Day is "Invasive alien species". Here is our pictured contribution: as reported as a side note in blog entry "Eremozoic Era" last month, we are currently dealing with a common invasive species in our backyard, which is trying to drive away our returning bluebirds (yes, the young from last year we suppose :)): house sparrows.
The quite fearless sparrows (except the one on the picture, once we trapped her inside the nesting box :->) are giving our shy wannabe-tenants (say: bluebirds) a hard time. We feel kind of bad taking out the sparrows' nests again and again - especially if they look as pretty as the pear-blossom padded one on the right, but ... why this still makes sense can be read on the "Global Invasive Species Database" :
Despite their small size, house sparrows (Passer domesticus) are quite aggressive. House sparrows are known for displacing native species through competition by out-competing them for trophic resources. In rural areas they may evict native birds from their nests. Some species reported as being driven away by P. domesticus include the bluebird and the Carolina wren, as well as a variety of woodpeckers and martins.
And sure enough - the fact they are here is just human arbitrariness. For the outcry "simply let nature go its way!" it's i.o.o. a little late - we should have done that 160 years ago. Sparrows, we read, were introduced into North America intentionally in the mid 19th century - "in 1851, when a group of 100 birds from England was released in Brooklyn, New York". A can of worms has been opened there - and our bluebird-efforts are an itsy-bitsy approach to get the worms back in this can.
However, the sparrows are a rather small issue compared to others, e.g. in Australia.
Seems Australia has been (and still is) the playground for humans to experiment with introduced, invasive species, others to counteract the first, and a third to hold all of them in check. Or so.
Humans helped nature to quite a zoo of non-native, introduced species there: rabbits and the red fox (introduced for some hunting pastime, being far more successful than the hunters), camels (imported as pack animals until the early 20th century), the cane toad (introduced in the 30s to get rid of beetles), lots of sheep (not feral or invasive, but they still heavily contribute to erosion) - and, sure enough, cats (see also blog entry from July last year).
Add some introduced, invasive weeds to that, and with the ecological mess you have a serious economical mess as well - adding up to billions of dollars* yearly just to somewhat control the damage and keep Australia a livable place for humans. (*WWF: "... Australia's multi-billion dollar feral animal and invasive weed problem ..." ).
In light of this hear somebody say "we do not need polar bears", or any other species (see also the FAQ). We obviously have little idea what impact species (or their absence) will have. We think we know enough to add or take away species from eco systems as we like. The past proves we do not.
This blog entry got more than just a few lines again. Apologize for the preachiness, as always. Here is the link I actually wanted to post: 5/22 is "International Day for Biological Diversity", this year's topic as said: "Invasive alien species ".
Gotta run - fighting our invasive sparrows! ...
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