We don't have enough trees to deal with all the massive amounts of carbon created each year, which is one of the major engines driving global warming. So what's the solution? Why, to genetically engineer better trees, of course.
Although we can't just destroy all the carbon building up in the atmosphere, nature can capture it and convert it into a more long-lived, less environmentally dangerous form, which can then remain in the soil and vegetation for thousands of years. Trees, plants, and algae do some of this work in photosynthesis, but we currently produce way more atmospheric carbon than can be naturally dealt with.
That's where a little nifty genetic engineering comes in. There are a number of different approaches we could take. We could increase a tree's absorption rate of light - and, with it, the amount of carbon it absorbs - or allow trees to sequester more carbon in their roots instead of releasing it back out into the atmosphere.
It also might be possible to make hardier trees that can grow on less environmentally friendly areas of land, allowing us to plant more trees closer to the major industrial areas, which create a lot of the excess carbon. Another idea is to boost the quality of the crops themselves, making them better suited for use in bioenergy and thus reduce our dependence of fossil fuels.
All of these ideas are examined in the October issue of the journal Bioscience - you can read the introduction here. The various researchers are generally in agreement that this work could be an important part of combating global warming, but it isn't a magic bullet and would only be one of many possible solutions we need to explore.