Weeds do become resistant to herbicides, and it needs to be managed with multiple herbicides.

If there are more and more environmental refugees, they are going to end up on your doorstep too.

There are probably already too many people on the planet.

We have six-and-a-half-billion people on the planet, going rapidly towards seven. We're going to need a lot of inventiveness about how we use water and grow crops.

As people around the world become more affluent, they are demanding diets richer in animal protein, which will require ever more robust feed crop yields to sustain.

We've gotten so good at growing food that we've gone, in a few generations, from nearly half of Americans living on farms to 2 percent. We no longer think about how the wonderful things in the grocery store got there, and we'd like to go back to what we think is a more natural way.

Even as the population doubled from three to six billion, we managed to race ahead with all kinds of technological and scientific events in agriculture - from using more fertilizers to mechanization to advanced plant breeding.