The elite few that are really running this world have this idea that the only way to achieve sustainability is to reduce our population down to less than half a billion and to concentrate those on 3% of the Earth's land mass or less. There is general agreement among them that people with inferior genes should be eliminated, via forced sterilization or outright murder, they have no problems with either. The elite have no concept of the sanctity of life let alone human life.
I think there is an alternate path to sustainability that can sustain larger numbers and can do so in a way that is much more pleasant, rewarding, and provides individual freedoms that their plan would not allow. It also comes with much larger responsibilities and requires a greater degree of personal growth than their plan requires. I think it is worth it.
There are two key elements, a clean nearly unlimited energy source, because we need to stop polluting the atmosphere and we need to concentrate our activities, particularly farming, into a smaller area to leave more area forested which the planet needs to recover. Second element is more of a philosophical one, perhaps also a spiritual one, we need to recognize that we are not opposed to nature, we are not apart from nature, we are a part of nature, this is the part that Agenda 21 or Agenda 2030 fails to recognize. On the spiritual level we need to realize we are all part of the same creation, maybe not created the same day, but part of the same whole. Agenda 21 / 2030 seeks to solve the problem of our assault on nature by separating us from nature, and this is entirely wrong. Instead we need to learn to co-exist with nature, to find our place in nature and live with it. This requires a mindset that says, not what is best for me, not even what is best for humanity, but what is best for the sum total of all life on this planet.
We have two potential sources of nearly unlimited clean energy that can scale to what we need to support a large population. Solar takes up a lot of real estate, Wind kills birds, and both of these sources are intermittent in nature. Geo-thermal is available 24x7 but not everywhere. But a combination of these can help us cut carbon dioxide emissions while we work on two technologies that can scale just about indefinitely. These two can largely meet our existing energy demands, but to restore the planet we do need to concentrate many human functions into smaller area, vertical farming, manufacturing, to allow more room for forests and grasslands and wetlands that other species need for their survival. With these existing energy sources and high voltage DC transmission lines and smart grids we can use geographic diversity to overcome the problem of intermittent supply to a large degree, and we can develop geothermal to a greater degree to provide more base load capacity. The fallacy that says we can't put more than 20% of renewable energy on the grid has already been disproved is several European countries where they have supplied 100% of their electrical needs for some periods off of renewables.
Years ago in the United States we had three isolated grids. I advocated for high voltage DC inter-ties so we could better take advantage of geographical diversity, now we have those. There are many other advantages to high voltage DC inter-ties. First, high voltage AC lines radiate a large percentage of their power away over very long distances, DC lines do not. This radiation is harmful to humans. Low frequency AC magnetic fields are associated with higher leukemia risks. If it is harmful to humans it's probably not good for other animals. The mechanism is that it interferes with the transport of ions through ion channels in cell membranes by causing the ions to spiral slowing their transport. Besides lower losses, another advantage of DC inter-ties is that they are immune to EMP and solar activity. The extra DC potentials induced in long lines are compensated for by the converters rather than frying transformers that have very little resistance to DC. But this is happening just because of the sheer economic advantages of not losing ten or twenty percent of your generated capacity in the lines. Also, converting AC lines to DC results in a substantial energy increase over the same wire. With AC, the insulators need to be designed for the peak voltage but the RMS (root mean squared average) is only 70.7% of that and the average power half, so going to DC can double the capacity of the line with the same insulators. Also, it improves current carrying capacity because one of the things that limits current capacity of AC lines is that as the current increases, the lines sag. As the lines sag they become physically longer and this causes a phase shift that ends up just wasting yet more power heating the lines. With DC lines phase and frequency are no longer a factor so the lines can be run at higher current levels potentially tripling capacity for the same wire running AC.
Smart grids with automatic load shedding of non-critical loads are another way to better utilize intermittent renewable resources. Renewable capacity can be expanded to meet the peak demands of essential loads during minimal production periods and then during maximum production periods that energy can either be stored via either pumped hydro, large battery banks such as those Tesla has manufactured for some municipalities, or by a type of battery in which the electrodes are liquid and the electrolyte is solid, these are known as flow batteries and their capacity is limited only by the size of tanks used for the electrodes.
These energy sources are short terms but to really allow the planet to recover, we need to be able to take some of the existing land used for energy production or farming and return it to forest or grasslands or wetlands, whatever existed prior. To do this we need yet more energy, this will allow us for example to build many story high-rises to do vertical farming, and the same is true for manufacturing and many other human industrial activities. There are two technologies that can provide energy for a very long time, the first which is more immediately deployable is a type of nuclear reactor called a liquid salt reactor. These reactors use fast neutrons rather than slow moderated neutrons to produce a chain reaction. These reactors are inherently much much safer than light or heavy water reactors. First, no graphite moderators means a source of big flammable carbon is not present so a Chernobyl type event can't happen. Second, in the event that active cooling fails this type of reactor will not melt down like Fukushima because of two inherent safety factors. First the fuel is dissolved in liquid salt contained in a tank so it already is liquid, this is the normal form of the reactor, and so fuel melting isn't going to destroy any structure since this is it's normal mode of operation. Then the reactor itself has a negative temperature coefficient, that is to say as temperatures increase the reaction rate decreases as a result of the physics not requiring any intervention. The liquid salt simply expands pushing the fuel farther apart from itself, so more neutrons are lost rather than participate in the reaction and the reaction slows. Lastly if in spite of this the reactor overheats, there is a passive safety device that operates. The reactor has two tanks, the reactor tank on top which is small to keep the fuel compact to react and generate heat, and below a much larger dump tank which is large enough so the fuel is spread out and the nuclear fission reaction stops and it is also large enough to dissipate the heat of the decaying fission products without the aid of active cooling. Thus if all active cooling and control is lost on one of these reactors the absolute worst case scenario is the melt plug melts and the reactor tank dumps it's fuel into the much larger dump tank and it cools off.
There is another type of reactor that is very similar but is somewhat less safe and this is the liquid metal reactor. The problem with these reactors is the liquid metal is very corrosive thus corroding plumbing and heat exchangers and then radioactive metals leak out, and if the heat exchanger rots through allowing water to contact the liquid metal, usually sodium, it can react extremely violently. If it comes into contact with air it spontaneously combusts, either is bad.
But both of these reactor types normally have on site fuel reproducing which basically consists of extracting fission products from the circulating liquid to keep it below a level where it poisons the desired fission reactions. Because this happens on site, there is no opportunity for terrorists to intercept spent fuel.
There is another reason we should build these reactors even if we don't need the energy. Nuclear waste consists of two classes of material, actinides, these are heavier than uranium radioactive elements that form as the result of neutron absorption, and fission products which are neutron rich and decay rapidly into more stable elements. The actinides are produced in conventional light and heavy water reactors and are the portion of the waste that makes it take up to a million years before it is decayed to a level where it is safe to return to the environment. The fission products decay rapidly and reach a point where they are safe in only about 300 years. These reactors "burn" all the actinides, which is to say fission them, fertile actinides are burned indirectly, they first absorb neutrons, become fissionable isotopes and then do fission. These reactors can take the waste from a light water reactor and generate almost 100x as much energy as the original reactor did from the fuel, and turn a million year problem into a 300 year problem and further can greatly reduce the bulk of the waste as well. We could meet the planets energy needs for the next thousand years or so by just burning the waste we already have from existing reactors. The remaining uranium and thorium deposits on Earth could provide for our energy needs for at least 100,000 years. We have already built demonstration reactors that work so this technology is not iffy, it is something available to us now. The current Department of Energy plan for Hanford is to just cover the waste tanks with concrete and allow all that high level nuclear waste to seep into the Columbia river further polluting the Pacific Ocean and rendering the residents of Portland Oregon, who drink water drawn from that river, radioactive and cancerous. It makes much more sense to use that waste to generate energy and destroy it.
The second option for clean unlimited energy is controlled hydrogen fusion. There are many variations here but the most reachable, that is to say the reaction we will probably be able to take advantage of first is deuterium-tritium fusion, often referred to as dt. The reason for this is the energy required to get these two atoms to fuse is the lowest of any combination we know. The disadvantage of this reaction is mots of the energy is carried off by fast neutrons which then is absorbed by a lithium blanket regenerating tritium as fuel and heat. The heat is used to boil water and drive turbines and the efficiency of this process is around 40%. Two better reactions involve substituting he3 for tritium, this results in no neutrons and the energy is carried off by charged particles that can be directly and much more efficiently converted into electricity but he3 is scarce on the Earth but more plentiful on the moon which makes this fuel more practical after we've further developed space travel. Another option is hydrogen beryllium but this requires much higher energies to fuse so is a down the road technology. There have been two recent breakthroughs in fusion research that promise to make build-test cycles much faster and fusion machines much cheaper. The first is a new magnetic configuration that Skunkwork groups at Lockheed have developed. This configuration is such that field strength increases near the edge of the plasma rather than decreases as in a Tokamak. This allows higher temperatures and plasma pressures for higher fusion rates in a much smaller machine than a Tokamak. The second breakthrough is a new super conductor material that allows double the old maximum super conductive magnetic field strength. The new YBCO materials can produce fields as high as 32 Teslas, the older super conductors couldn't produce more than about 15 Teslas in most applications although the previous record field was 23 Teslas. These new materials also are manufactured in the form of a ribbon which can be much more easily would into coils. Because confinement improves with the cube of magnetic field strength, doubling the field improves confinement 8x allowing for a much smaller device. Because the smaller machine is much less expensive, design/build/test cycles can be much more frequent allowing us to perfect a working machine much sooner and more economically than we otherwise would have.
There are other approaches to fusion that use inertial rather than magnetic confinement. It's my belief that these will not be economical. They have achieved scientific breakthrough as has magnetic confinement but scaling that up is not as promising.
So assuming we can get one of these energy sources online then we can realistically do things like vertical farming, things like tunneling become cheaper and that makes underground transportation, wiring, etc, more feasible which improves the prospect of us living along with nature without running it over with our cars or requiring that we pave everything over. With cheap energy we may exhaust other materials sooner, but with cheap energy making cheap rocket fuel and mining asteroids becomes more practical. Because asteroids are usually not large enough for gravitational separation to occur, heavier elements like gold, platinum, etc, are much more accessible than on Earth. Anyway, hopefully this will provide some food for thought.