I remember being struck in a sci-fi novel by Nancy Kress where she described a special GM grass that was the most effective biosystem to transform nutrients into organic matter (itself), and was thus an incredibly energetic crop. The problem was of course that this grass, if left alone, would have taken over the whole planet (except a few large trees wit hvery deep roots) and killed every single other crop.

In the long run, we're all dead. John Maynard Keynes