vegetation and vegetables

I tried going to a coffeehouse talk tonight on the effects of climate change on tundra vegetation, but it was sunny outside and, while interesting, the talk reminded me of a school lecture. The woman giving the talk detailed ecological zones, explained why one would expect vegetation to change with warming temperatures, and said the growing season is starting about 10 days earlier than 50 years ago and ending at about the same time. She passed around bags of dried plant matter collected from tundra patches.
At home, I finished my own growing project that I've been working on for the last few days. I bought some baby plants on Saturday -- basil, peppers, cabbages, and so on -- and decided to build a greenhouse for them for reasons I don't quite understand. I guess I hope they'll grow better, but I also just liked building the thing. Last year I started growing from seeds and got quite a few tasty carrots, but didn't have much luck with the cukes or herbs.
Any gardening advice is much appreciated!