Query about Mars

I was musing about the following situation, maybe someone can offer
some thoughts?

WRT to Mars my current understanding is that the climate is harshly
carbon dioxide (is it?). If it is then we know that trees and plants
can change carbon dioxide into more friendly climatic gasses for human
habitation.

So if there were water deposits found on Mars, how viable would it be
to engineer some serious vegetation on the planet so that the
atmosphere starts to develop more human friendliness? Obviously the
vegetation would also need its own life support systems such as
insects and so on, so it would generally take rather more than a
packet of seeds from the garden centre.

I appreciate it's not an overnight change, and it could in fact be
hundreds of years (or longer) before the climate was friendly enough
to support human life.

The question is purely rhetorical as I'm interested to know if this
would be a feasible option.

Andrew

Problems scheduling resources? Check out
KazPlan Enterprise and Personal Editions!
at http://www.kazmax.co.uk/OurSoftware.asp