Sorry, I meant to say peat swamps, not boreal forests.

Regarding peat swamps, they are less valuable in that the land isn't being farmed. Transformation of "unvaluable and useless" peat swamps to productive oil palm plantations often, but not always, involves altering the water table of the forest, which causes a massive increase in CO2 (peat is an incredible carbon sink) as well as widespread fires.

http://www.scientificamerican.com/article/peat-and-repeat-re...

http://www.dw.de/peat-forests-pose-major-climate-threat/a-52...

https://en.wikipedia.org/wiki/Southeast_Asian_haze

Seems like the easiest solution is to make the land valuable in its current form. In the US there's a federal program to control the amount of wheat produced by paying farmers to let their wheat fields lie fallow. I assume though that a palm oil plantation is quite a bit more valuable than a wheat field.....

Yes. You're missing the chapter in your economics textbook titled "externalities".