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.
Don't people engineer new biomes pretty frequently? It seems pretty defeatist to look at a world where we regularly transform dirt fields into grassy plains into food and think that we'll never be able to sustain ourselves if the climate changes.
Engineering new biomes for fun is different than having to do it every year or you die.
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.
