Hi just wondering what do you teach? Econ?
Desalination will work in the short term; I am not a biologist, so the implication to sea life was something I didn't realize until now. But I would imagine it would definitely perturb the system to the point of a chain reaction.
We would need to desalinate a fourth of the Atlantic to satisfy the world needs for the next 100 years - if the water shortage is as severe as thought. But, if we stop cutting down trees we will have more filtered water cleaned by UV radiation, and gently dropped from the sky.
I think it will come down to a global maturity issue:
stop building cities meant for profit instead of longevity (i.e. wood vs stone houses)
stop hoarding the majority of resources for the super-rich only (there are plenty of resources for 100 billion people; we just cluster in cities where we leech the land an resources exponentially - giving the impression of overpopulation)
Stop allowing leaders to continue razing land through wars for profit, and telegraphing the cost onto the people
Get over racism to the point where it can be confronted, resolved and ultimately reverted to simple prejudice (very different from racism).
Learn trades of self-sufficiency.
Eliminate fiat-based currency systems
If the world can do those basic activities of maturity, then we would realize how rich we all are, and we wouldn't have to connive and scheme just to get $1 more than the next person.