We may feel that the effects of "overpopulation" will not overly affect us...and this is true for the current generation.
Canada is considered underpopulated, so she is actually taking in a huge amount of immigrants to deal with the current "ageing population", about 250,000 annually, there are also other countries which are doing the same (the worldwide figure is about 200 million annually- the largest being Europe 70 million, North America 50 million, and Asia 25 million). But at some point they will all reach their saturation point and stop. When this happens "population shifting" will no longer ease the situation.
Theoretically, scientists are close to making cars that run on hydrogen, and exhaust pure water.
I myself am headed to the car dump as we speak with my bucket to gather drinking water.