Why be concerned about the year 7,000 CE (AD for old folks)? Because that’s about half way to 12,000 years past the present and why that date because it is the same number of years since back to the beginning of the Holocene. That Holocene date is the end of the ice ages and the beginning of agriculture and modern human society. It’s a fixed and measurable point in time.
A simplistic calculation estimates that humanity is half way through its life expectancy. Why choose half way for some unknowable process? Because of all of the species who have ever lived almost all of them have gone extinct and if we were to look at any one of them we would probably be dipping into the central portion, when they are alive, and an average that will be half way through their existence. Maybe on one end or the other of the middle half but if we choose civilized man that extension of reference zone would only inserting 7,000 years ago and 7,000 years into the future for this arbitrary but fixed date. That would be 5,000 CE and 7,000 CE. Thus, just for a guess for where civilized humanity is at in its life cycle saying half way is reasonable for most geological purposes. That estimate gives us some solid perspective on where humanity might consider itself. That fixed date gives something better to work with than just floating about somewhere between zero and infinity.
Using an exact date gives us some idea of what the promethean word sustainable environment might mean and what humans as a group should be considering relative to the environment. One thing becomes obvious when looking at humanity this measured way and that is that it can not carry on the way it presently is for very long. When politicians use the word sustainable when referring to the environment they generally mean something relevant to their political career. Usually to them that means the next election and rarely does it mean so long a period of time as the life expectancy of their youngest voters. For a young voter, say age 20 with a normal life expectancy at that time sustainable would mean would mean a period of 70 years of balanced environment. Something becomes obvious. When politicians talk about sustainable, like sustainable oil production being secured by drilling some more oil wells they are clearly lying because even a perfunctory scan and a bit of thinking about world oil supplies shows that no informed person will claim there will be the same amount of oil as is presently being pumped from the ground being produced continuously for another 70 years. Sometimes, some of the experts will say 20 years but it would be hallucinating for them to say 70 years or bare face lying.
With that little bit of speculation about time of oil production, other things could be used, compared to my hoped for projection for civilized humanity continuing for say 7,000 years a simple calculation of dividing 7,000 years by 70 years gives a minimum of a multiple of 100 times error of that possibility. It is like telling your girlfriend you are going out to dinner and you have $70 in your pocket for dinner and a movie but in fact you know you have only $1 or less. She is going to have a rude awakening at some point during your evening together and some serious disappointments. Your lady friends estimate of your worth and your sanity is going to plummet.
Humanity is in for a rude awakening of the same type and some serious readjustments as to how we are going to live. We can probably live a very satisfactory life style that has many components of our current high-tech civilization but it is very unlikely to have gas guzzling cars, airplanes and farms. Yes, farms because they consume lots of oil in the form of equipment and fertilizer.
There will be some changes, that is inevitable but what could those be which in the long run will bring about the maximum of human happiness. To start with the whole human population of the Earth would have to be regulated at some much smaller number than it is at present. A nice round number would be something like 100 million. In any case it must be regulated to some number which would be determined by those people at that future time but they must do it because even a small group of free breeding people would expand to our present population in a few centuries. They must be limited or there would soon be the same overpopulation problem and crisis and collapse which we are about to experience. On average each person in this sustainable society would have two children and that should be sufficient to calm any desires for unlimited fecundity.
Another problem is armed conflict with weapons of annihilation such ah H-bombs and bio-weapons. These are now available and with the current mind-set and political institutions the will eventually be used. However, when one thinks of a 7,000 years of future civilization these devices simply can not be available they must some how be contained and even the information on how to make them must be isolated and the materials that can be used to make them must be monitored. Anyone obtaining any of those things would have to be isolated permanently as untrustworthy. No one has the right to be able to destroy humanity and those who seek that ability need to be thwarted.
For humanity to live for 7,000 more years it appears that either they are reduced to a primitive condition which occasionally percolates up to a technical civilization which destroys itself again as we are presently doing or a sustainable population finds a way to live in balance with the capacities of Mother Earth.
A sustainable stlye of living will ultimately produce more human happiness.