Go on then, name just one crop that was bio engineered in the 1800's please. (bio engineered - DNA profiled and structured to be resistant to whatever was the issue back in the day)
We didn't have the ability to change things gene by gene back then, but it doesn't mean we didn't do extensive manipulation of crops via breeding to ensure they met out needs. It's like saying a battery farm is a natural place just because they have chickens in them

Do we look to prevent/tackle global warming or adapt to anticipated changes?
You have 100 billion pound, all of which has to be spend on either preventative measures or on ways in which we could adapt to anticipated changes. What would you go for?
As said in my answer, I'd forget climate change and spend the money on other environmental issues of greater importance, that just so happen to do both prevent/adapt, whilst being far easier to sell to the population than the hornets nest of climate change.