[pbh101]

Yes. My father does research in this area. Specifically, inferring the health of vegetation (among other attributes of land cover) from statistical analysis of satellite imagery.

From what I recall, you can measure the level of photosynthetic activity in an area given the reflectivity of the land (and, I would think, some basic model of what type of vegetation is present in the area)

One example from his research: the fall of the Soviet Union had a statistically significant impact on weather patterns in Kazakhstan (the breadbasket of the USSR) because the land usage changed so much with agricultural policies before and after the fall.

Quick link to the research overview page: http://globalmonitoring.sdstate.edu/research.php