In a general sense, I already established what the solution is, which is to let the free-market system find solutions; it has a well-established track record for doing this. Religion and government, on the other hand (and as I already showed), has a well-established track record for causing and preventing solutions. Sometimes the solution is simply to do nothing more than get government and religion out of the way.
The free (ie: unregulated) market is one of the major
causes of the problem. It has little interest in finding solutions. There's no profit in it. They are more motivated by increasing production and the next quarter's market returns.
Only government has the power to monitor and regulate this.
Government has a long history if trust-busting, market and environmental regulation. It's been since the Neoliberal revolution/Reaganomics that government has been captured by the Banks and corporations, and protective regulations rolled back.
As for specific solutions for fresh water and topsoil (and I'm only going to focus to the ones pertaining to population sustainability, since that's what this thread is about), there are ways to produce fresh water such as using reverse osmosis with seawater;
And what's to be done with the waste brine?
with the topsoil issue, the basic problem for population sustainability is food production, and some of the solutions for this are aquaponics, hydroponics, and vertical farming; there are also red and blue LED grow lights, which are energy efficient for indoor gardening.
These are good ideas, but are they feasible everywhere? What' going to motivate corporations to spend the capital to fund such large multinational projects? It's like pulling teeth just to get them to install scrubbers on the stacks of their existing coal plants.
As long as there's capitalism, money, trade, markets, and scarcity in general, there's an economic need for the state, government, and laws, but only to function as a referee that respects rights and protects victims, not to impose central planning and command & control of the economy.
But who's advocating that? It had a pretty poor record in the USSR and Red China.
Government, as regulator of consumer and environmental protection, a bulwark against monopoly, &c, is what corporatists and captive government opportunists have been attempting to "drown in the bathtub" for the past 40 years.
"Free trade" = freedom from
regulation, and a return to the exploitative, wild West economy that preceeded the Great Depression and subsequent rise of Authoritarianism.
That's what economic socialism is, and at best it scales up very poorly from a population larger than Dunbar's number.
It scaled up pretty well in the US and western Europe during the post war years -- at least until Reagan and Thatcher's anti-government deregulation began
undermining the prosperity, security and opportunity of the 99%, and the money began 'trickling up' to the one-percenters.