Our efforts to intentionally alter our home planet have been unpredictable at best. Can we terraform other planets without making the same mistakes? Should we?
We've seen how things can go awry when we tinker with our planet, but geology is fairly resistant to short-term change. When we screw with ecosystems, however, the chain of effects can be long and extremely unpredictable.
Humans can rearrange the shape of our planet almost as easily as the furniture in your living room (or the deck chairs on the Titanic). Of course, it doesn't always work out as planned.
We usually think of terraforming as something we'll do in the future to other planets, but we have thousands of years of experience changing the shape of our own planet in profound ways.