well-to wax philosophic on a local basis....Tucson has well water that can supply a population of 35,000 persons on a sustainable basis. We have a population of about 1.5 million...and growing. If we just used well water,our inventory that took millions of years to accumulate would be gone in 8 years. So, we built a canal to pipe water from the Colorado river...and our allocation is 2.1 million gallons per day, about enough for 2.1 million souls. Our allocation is at risk - California wants it, and if you add California allocation to ours, the river cannot sustain that vol. Our politicians want growth to build houses and sell loans- not restrict growth to match water supply. Somehow, our use patterns must shift to make room for newcomers. Take my savings and sell it to the next guy.
I contend overpopulation is looming in my desert and I see no efforts to plan for it.
Southern California and the Southwest in general has a low natural load carrying capability because of the water situation. My mother grew up in Los Angeles and my father moved there in 1940. They both remembered the water wars that started in the 30s to get enough water to LA to support its growth.
Some people in California have proposed tapping the Columbia River here in the NW to send to Southern California (about a 1000 mile journey) which fuels the anti-California sentiment here in the NW. Oregonians and Washingtonians are very protective of their natural resources, especially the water. The two states have drinking water standards that I believe are much stricter than most of the US. Seattle and Portland have large swaths of the Cascade mountains that are closed off to humans which are the watersheds for those city's water supplies.
Keep in mind that:
a) India is currently the densest populated country that is self-sufficient in food and water (with current technology).
b) If you extrapolate the Indian population density to the habitable landmass of the world as a whole, you get to 9.5 billion people.
It's a change in lifestyle to many of us, but not an outrageous change - certainly not one that most people would go to war for. There are plenty of countries where 95% of us would be happy living in that has a similar or larger population density than India - e.g. UK, Belgium, Italy, South Korea, Switzerland.
Our biggest obstacle isn't our planet, but our unwillingness to solve our own problems. Saudi Arabia has virtually no land-based water, yet it has no problems obtaining water. Why do we have problems in California?
Saudi Arabia does get a significant amount of water from desalinization, which is very energy intensive. California could build desal plants fuels by solar, but California's water needs are significantly higher than Saudi Arabia's. Saudi Arabia has a population over 30 million, which is significant, but they have few industries that require water like manufacturing and virtually no agriculture. California agriculture can be very inefficient in its water use, but there are a lot of efforts to make CA farming more water efficient.
California uses over 100 gallons of water per day per capita. Saudi Arabia uses about 70 gallons a day. (Closer than I thought when I looked it up.)
India is able to support itself for food now, but its running out of ground water. The problem we're facing worldwide is we're only able to support the 7 billion people we have now by using ground water which is being used up at a rate 1000 times faster than it is being replaced by nature. That's one reason I say the long term carrying capacity of the Earth can't support 7 billion people. We may be able to make some fresh water by deslinizing sea water, but that is very energy intensive and it's going to take a big growth in solar and/or other renewables to support and it still doesn't help places that are some distance from salt water like Tucson.
The growing region in India is way up in the north a long ways from the Indian Ocean. They would have to put in huge desal plants along a coastline that is already crowded, power it with new renewable installations, and then build mega pipelines to move that water up country. It can all be done, but it will be a massive engineering project and it's going to be very expensive.
This would have to be done in a lot of countries. If ocean levels do change, then the desal plants may be put underwater, or if the climate gets colder, which may also happen (the ice core records show that over the last 2 million years 90% of the time the Earth has been much colder than it is now and just before a glaciation period starts, world temperatures go up) the desal plants may be left high and dry. Though some places like Southern California and the SW US would see significantly more rain than they see now. The geologic record shows that the entire western part of North America gets staggering amounts of moisture during ice ages. The entire state of Utah was a giant lake (Lake Bonneville) during the last one. The North Pacific gets warmer during ice ages.
Human nature is to stick its head in the sand until a problem is severe then scramble to try and fix it. I saw a story on the documentary series Vice a few weeks ago that the Indian government isn't willing to do anything about the children living essentially on the tracks in the Calcutta train station. That's a much easier problem to solve than running out of ground water and building the infrastructure needed to replace it with desalinized water.
