On Wed, 15 Feb 2012 08:32:51 -0600, Michel Boucher
> wrote:

>Boron Elgar > wrote in
:
>
>>>Here's an argument anyone can understand. Bacteria and worms
>>>are necessary to agriculture. But bacteria and worms do not
>>>migrate, so how is there going to be arable land on top of
>>>rock and moss if the natural manufacturers do not make the
>>>trip northward?
>>>
>>>Well, the answer is simple. There isn't going to be any.
>>
>> Worms migrate. Some are quite invasive and they do, indeed,
>> spread. Some of the introduction is natural, some accidentally
>> assisted, but those guys get around.
>
>But they get around in soil. For them to reach the barrenlands of
>northern Canada to start the process of breaking down the material
>to make useable soil, they would have to cross vast distances in
>which they would find no sustenance. If they even knew which way
>to go.
>
>Perhaps in a million years or so.

Unless we and all our commerce and movement cease, it'll take much
less time. And even on their own, some manage 10 meters a year. Your
million years is way, way off.

http://partners.nytimes.com/library/...imal-worm.html

Boron