To be able to make such predictions, we have to make certain assumptions about the future. These assumptions are:
-Industrial civilization is a temporary phenomenon. A beginning at explaining this principle is explained here.
The general point made is that human industrial civilization is made possible by high-grade, easy to extract resources. As our civilization progresses, we become capable of utilizing less pure resource forms at greater fossil energy costs, and carrying out the same tasks with greater energy efficiency. However, we have rapidly run into barriers. We never become capable of recycling 100% of a rare metal, and will never build a universal mining machine to use the abundant copper in our crust, because it would simply take too much energy.
Important to understand is that we did not build Industrial civilization because it benefits us in any way or makes us happier. Industrial civilization emerged because every lifeform is oriented towards the same goal: Namely, to usurp as much available energy as possible, as doing so ensures that other lifeforms can not use this energy to compete with us. On the short to mid-term scale this can be disastrous (global warming), but on the long-term scale, it benefits the biosphere as a whole (an increase in bioavailable carbon eventually increases the total biomass on our Earth). Hence, if a form of energy is available to us, we will inevitably find a reason for ourselves to utilize it. We will feel for example a psychological desire to drive in cars as big as elephants that drain our wallets for reasons we may not understand directly ourselves.
-When industrial civilization collapses, it will be impossible to rebuild it. This point has been adequately explained by multiple people, including Jason Godesky and Theodor Kaczynski.
Kaczynski explains that complex technologies such as nuclear energy and the internet were only made possible by the development of earlier simpler technologies. Hence, after a collapse, before reaching our current point, a reliable stable system for generating complex tools will need to be rebuilt before we could ever reach our current level of technology again. Kaczynski also mentions how the industrial revolution was a rare phenomenon that emerged for complex reasons that are still not fully known. Although other civilizations such as the Indian and the Chinese were theoretically capable of entering the Industrial revolution, those societies did not do so.
Godesky explains that the resources that were used during the beginning of industrial civilization no longer exist. High grade metal ores, surface oil fields and coal mines, all of these are gone. We are only capable of utilizing deep oil fields and coal mines, and low grade ores because we used easier accessible fields and mines to create the tools required to reach the deeper ones. Our descendants will not have most of those tools.
-Humanity will survive the collapse. Explained by Godesky here. This is the most difficult point. It is true after all, that we are now theoretically capable of destroying our planet through the use of nuclear weapons. We came close to that point during the cold war. However, it can be argued that nobody will have an interest in doing so, because to do so would be to sign your own death certificate. Furthermore, such decisions are not made by individual persons, but require consensus of large groups of people. This is not to say that nuclear terrorism or other small scale events may not happen.
Luckily, resource scarcity has the unintended consequence of reducing our stockpile of nuclear weapons, because the weapons contain uranium that can be used to fuel nuclear reactors. Because Uranium is scarce there is a great financial incentive to countries to reduce their nuclear stockpile.
Biological weapons are unlikely to ever succeed in fully eliminating the human race, as random mutations will ensure a minority of people are resistant. Diseases such as HIV which emerged in sub-Saharan Africa are incapable of infecting a minority of Northern Europeans who happen to be naturally resistant due to medieval exposure to the plague. Even in the unlikely event that nobody carries natural resistance, the fact that uncontacted human tribes still exist indicates that such a disease would likely burn itself out before being able to reach every human community on the planet.
-Chemical weapons are useful to exterminate large densely populated communities of human beings. However, they are less useful when trying to use them to eliminate sparsely populated communities of hunter gatherers. North Korea could be quite capable of ending Seoul, but it would be less able to end the Inuit.
The most important point to remember is that any human power structure that is theoretically strong enough to end human existence rapidly eliminates its own ability to do so in the process of attempting it. Pollution for example would likely destroy the society generating it before being able to raise pollution levels to a high enough level to affect all people living outside of civilization.
In general, species and human ethnic groups that go extinct do so not due to their own mistakes, but due to autonomous outside entities that are not dependent upon them. Hence we would be wise to fear artificial intelligence more than we fear nuclear weapons.
To understand this, we first have to understand what will happen to our environment in the absence of civilization. The answer will not be human extinction. Instead, we see a rapid decline in the complexity of our civilization, towards a level that is more similar to the level of complexity that we have evolutionarily adapted to survive in.
The level of complexity that we are adapted to differs depending on the type of environment that our ancestors evolved in. As an example, many Indigenous Americans are not evolutionarily adapted to agriculture. For example, they have no genetic resistance to many of the illnesses that occur in human societies that live under high-population densities. Their immune system is less adapted to illnesses that spread from person to person. Hence, many of these tribes are wisely xenophobic.
Similarly, Australian Aboriginals and other recent hunter-gatherers are poorly adapted to a diet that is high in easily digestible carbohydrates. Such diets lead to obesity, early puberty and epidemics of diabetes in these people. On the contrary, Europeans and especially East-Asians are relatively well adapted to agriculture.
Part of the difference in evolutionary adaptation to agriculture can be found in differing rates of schizophrenia. Only two schizophrenics were found amongst 65.000 people in New Guinea who did not practice agriculture. Low gluten diets appear to benefit schizophrenics. Furthermore, a link has been found between schizophrenia and celiac disease. Immigrants to Western countries often suffer from elevated rates of schizophrenia, and so do their children, both when compared to their country of origin and their current host country. It is likely that they are poorly adapted to our diet.
Considering this, it may be interesting to ask ourselves what will happen to human agriculture after the collapse. The first thing to note is that through our burning of fossil fuels, we have raised levels of CO2 to levels that did not exist anywhere in the past 20 million years. As hinted at earlier, although this will be disastrous for us in the short term and will likely disrupt our civilization, in the long term it was essential for survival of life on our planet that the human species increased the amount of bioavailable carbon. Although the short and medium term effects should be clear to all, it remains to be see whether on the long term scale it may benefit our species.
The reason is because carbon as an element has a tendency to slowly seep away from the biosphere. A small fraction of carbon compounds of dead organisms during various time periods for various reasons is not metabolised by other organisms. This carbon is stored in various forms in the Earth, and known to us under names such as natural gas, coal and of course, oil. In the case of coal, it appears that many plants were not being digested, but instead turned into bitumen, also known as brown coal. Eventually a fungus emerged that was capable of digesting these plants, and hence the deposition of coal into our crust ended.
The effect this "seeping" has is to force life to evolve to adopt to conditions of increasingly little atmospheric carbon. If the coal depositing had continued it would have been a disaster, as our planet would have eventually had massive coal depositions but no life. The low atmospheric carbon concentrations recently led to the evolution of a new type of plant that is capable of getting carbon out of the air in a more efficient way. This is called the C4 carbon fixation mechanism, and it allows certain grains to grow under conditions that would otherwise make plant life difficult.
Scientists disagree on whether climate or CO2 concentrations play a bigger role, but agree that grasses (which make up 85% of our agricultural crops) grow comparatively better under low-carbon concentrations. In fact, grasslands did not exist for much of our planet's history, due to higher CO2 concentrations back then.
Hence, we can ask ourselves what the human species function in our environment as a whole represents. Our function as a species to the rest of the biosphere is to function as "carbon liberators", to form a counter-balance to the general trend on our planet of CO2 concentrations declining. It is grasses that make our civilization possible, because in environments with few grasses, modern civilized lifestyle does not emerge spontaneously.
Even if we decided to stop all of our activities today, kill most people on the planet and return to a hunter-gather lifestyle, this would not end our CO2 emissions. The reason is because our digging in the Earth has exposed large number of underground coal mines to the dry atmosphere. It is estimated that 3% of global CO2 emissions every year come from underground coal mine fires.
Even with our current technology, coal fires are difficult and expensive to put out, and many fires have been burning for more than hundred years. Coal mine fires in deep underground mines can emerge due to exposure to the atmosphere through ventilation, which would not occur without humans. Importantly, rising temperatures and reduced moisture in the air increases the risk of coal mine fires emerging spontaneously. Hence, when human civilization collapses, coal fires will continue. Our rapid and short burst in global CO2 emissions will be followed by a long "tail" of CO2 emissions that will consist of coal mine fires and will continue for a very long time. Luckily, if those CO2 emissions are spaced out over time instead of being rapid and intense, the biosphere will be better capable of adjusting to them, and the effects will be less disastrous than our current "carbon burst".
A similar human interference that we have seen is our rapid liberation of phosphate from rock. We used to mine Guano to fertilize our fields as it was rich in phosphate, but eventually ran out of it and become forced to mine rock phosphate. This rock phosphate is mined in countries like Morocco and used as fertilizer. Animals used as food by humans then eat the plants that grow on the fertilized fields, and their manure eventually seeps into the water. Hence we suffer from eutrophication in the water and algae blooms. Although in the short term this is again disastrous, in the long term, it will eventually allow an increase in biomass in our oceans.
Similarly, elements that currently occur mostly in dense deposits are spread over the crust of the planet by the human organism, allowing their incorporation into other species for which they are currently a limiting factor. As an example, our mining of iron is used to make iron tools that eventually rust. This rust will end up in the soil, where it will eventually be incorporated in plants. Iron is an important element for life, and often a limiting factor for certain species (algae). Hence our mining of iron will likely also increase the total amount of biomass on our planet.
All these rapid changes occurring now will be met by another trend, namely, rapid evolution. Organisms, both human and non-human will have to rapidly evolve to enter new emerging niches. In the short term we are witnessing many extinction events, but this current decline in biodiversity will be compensated for in the future with an increase in biodiversity. We will temporarily live in a planet of weeds, but these weeds will be forced to adapt in various ways to their new environment, and will simply serve as the ancestors for a new branching of life into various directions.
Our cities are currently unique ecosystems, and will continue to be so in the future, serving a variety of unique lifeforms. Many of our concrete structures are overly strong, being constructed to be able to maintain more than their own weight without having to fear collapse. Lifeforms will evolve to inhabit the tunnels we have created under our cities. Already, a type of mosquito has evolved that only lives in the underground metro systems of European cities.
This is a new species of insect that has evolved in less than hundred years. Assuming that we do not destroy our underground structures (and we will have no incentive to do so), the persistence of these underground structures for the coming centuries will allow the evolution of new underground cave-like ecosystems.
The reason humans eliminate other lifeforms from their shelters is because failing to do so invites other lifeforms to join them, to the point where the shelters become dangerous for us to enter. Rats, bats and pigeons can carry diseases, fleas bite us, and ants steal food.
In the future we will be unable to eliminate these "pests", because there will simply be too few of us to eliminate "pests" from all our deserted structures. Furthermore, we will not have the pesticides that we currently use for such purposes.
Buildings will become overgrown with fungi and plants, birds will build nests in them, and animals in general will use them as shelter from extreme weather, while bats will hide in them during the day. Instead of seeing themselves as powerful destroyers of ecosystems, humans will finally understand that their true role was to become creators of new ecosystems, whether they want to or not.
Even when believing themselves to have escaped out of Nature's clutches, their temporary roaming across the planet was part of Her plan all along.
Via Khannea Suntzu