So that’s the past and the present.  What does the future hold in store.  In addition to the necessity of feeding as many as several billion more people using the same amount of land  we’ve been cultivating for half a century already, we are faced with a warming climate.  The Earth has warmed over the past 100 years by about 0.85o C. It is, by now, not terribly contentious to say that this is caused by the activities of people, largely by adding carbon dioxide and particulate carbon through burning fossil fuels, as well as wood and other biomass.