The problem doesn't really stem from North America, Australia, Europe, and parts of Asia. These places have low birthrates. Dangerously so in some areas. We need to tackle and properly regulate Africa, large parts of Asia, and parts of America.
-Invest in more efficient use of fossil fuels
-Invest in alternative fuel sources, especially solar power
-Massive oasification
-Create a stable, economically independent Africa, South America, and Asia.
The first three will reduce the impact of the fourth, which is the most important part. Birth rates decline as wealth rises. Girls in parts of Africa are already highly discouraged from having children young because mothers worry it will cut into their chances of going to college. That stuff has to become normal. It would help if the Catholic Church would just bite the bullet and allow people to use contraceptives. It's not doing Africa any services, and condoms would go a long way to getting the birth rate down to around a good 2.
Even if there wasn't social or political unrest in large parts of South America and Africa, there's still the problem of a lack of good deep-water ports and current trade routes. Most trade goes through the Suez and Panama canals, which bypasses most of Africa and South America entirely. This is starting to change, Brazil and Nigeria especially, but there's a long way to go.
Unfortunately, this will probably take a chunk out of Europe and North America as competition for resources rises which we might not be too keen to take.
