Time for a little population control. 
I really don't see why we had to find a cure for AIDS-it could've helped kill off some of the excess population that are taking our resources. 
Yes, we're joking. However, by 2050, we need to have a settlement on the moon in order to being either off-planet housing and/or agriculture. By 2100, I doubt that the world would be able to sustain such a large population of humans without having shortages of food/resources, unless we get some Star Trek tech going where we can resequence proteins into food and save the vast natural lands for something other than farming.
