A lot of guesswork without facts
I grew up on a farm with a lot of hogs. There's only one or two diseases that commonly move between humans and hogs, the worst by far being the flu. That said, I spent literally spent thousands of hours over 18 years treating sick hogs that had scours (dysentery), swine flu, various strains of pneumonia, etc., and never once got sick from them (in fact, I hardly ever got sick at all in all that time). The idea that global warming will cause more diseases to be transferred between humans and animals is mere speculation at this point.
The same goes for the effect of global warming on crop land. Sure, some areas will lose, but other areas will gain. The US might be a net loser, but vast areas such as Canada and Russia could certainly use longer growing seasons. For example, around 20,000 years ago natural climate change caused the rains in equatorial Africa to shift north and transform the entire Sahara into one of the most fertile areas on earth. The deep aquifers that exist under the Sahara today are the remains of large lakes that existed during this time.
