In the movie Interstellar, mildew was the straw that broke the camel‘s back for agriculture. From what I‘ve read, this can be a possibility if CO2 rises too high.
And it was somehow easier to move people and farms to a giant space station than to build climate controlled greenhouses on earth. But it looked stunning in the movie..
The space station was an arc traveling to the new planet they found.
People also got sick and died from dust particles, I guess the conjecture was that earth would soon become uninhabitable.