Once the animals are gone, we won't last much longer. It is extremely naive to think we can engineer ourselves a new biome that can sustain anything even close to what we have now.
What do you do when seasonal heat makes Pakistan and India uninhabitable for large parts of the year? We're not prepared for that kind of migration, we didn't even deal with Syria well.
Farming and other activities often require decades to truly show a profit. When rainfall patterns are changing on short timescales, you will not be able to plan for food production given the underlying churn in fertile locations.