> They're giving an opportunity for wealthier patrons to subsidize the pesticide-free production of food.

No, they are just defending themselves with crappy arguments. The real truth is people are lazy and do not (those who have the possibility ) want to grow vegetables in their back yard. They prefer to buy the cheapest industrially produced food from the supermarket. This leads to increased demand for crap food and indirectly to use of pesticides.

My point is that if it becomes popular among wealthy people to sponsor the conversion of productive farmland into what is essentially wildlife preserve then food prices could go way up, threatening food security.

Highly unlikely, rich people give a significant amount of money to charities but in general it's a drop in the ocean compared to the overall economy and government spending. I wouldn't worry about it too much.