The most obvious problem with the world is the number of humans who rule over it. If there was any way to magically reduce that number without some kind of holocaust or apocalypse it would have already happened. There are not many who would simply murder everyone indiscriminately, however there are a few -- people who want to nuke everything instead of solving the difficult underlying problems. There are also people to whom eugenics stills rings attractively.
The modern political parties are composed of many different mindsets, some based on religion, some based on money, some based on the environment, some based purely on military power, etc. Almost all roads lead to money, since almost nothing can be accomplished it, or without some kind of economic system. Of course a barter system could be established but that requires massive exchanges of physical items, with all the attendant energy needs and immense labor. This works for many of the rich countries possessing coal, oil, gold, industrial metals, gems, foods, and so forth.
The US has huge amounts of agricultural products that we trade around the world for whatever things we want. This depends on technology in the current age, which in turn depends mostly on oil and coal. Our huge amounts of coal may be of some comfort to us, however the amount of oil in the world is becoming more technologically and economically difficult to sustain. There is also a lot of methane gas to burn in somewhat cleaner ways, although the sustainability of those gas fields are not much more stable than petroleum.
Ecological problems from the use of fossil fuels and overproduction of mono-cultured foods can be ignored for the sake of graphs and corporate profits, yet there are no possible ways to extend those graphs and profits indefinitely into the future without a tragic, apocalyptic crash.
It is not a problem that can be solved in time with our infinitely increasing population. The people in power, especially those with vast personal wealth, will try to hide from the problems, in villas and private islands with guards and roadside weaponry for as long as possible. After that becomes a useless technique, itself doomed to exhaustion of resources, then only the deaths of the majority of Earth's people can result, including many of the less protected wealthy in the worst areas.
Science did not invent human suffering, however it has been both the bearer of great relief and the bearer of great suffering, always unintended, always with a polarity in both the directions of good and evil. Weapons seem to always come first, either for hunting or for battles with other humans. Peace is attained for a while, during which more knowledge is gained, more weapons invented, more wars, and then, hopefully, more peace.
In this century, the 21st in our manner of counting time, we shall know in which manner science will bring about the apocalypse, or more hopefully, a readjustment of our relationship with the other inhabitants of Earth. Wealth will not help you because you cannot take it with you. Religion seems only to fan the flames of discord and offers little but prayer as a solution to profoundly difficult problems. One can always hope that God will grant personal miracles, preventing a plane wreck from harming a single surviving child for instance. If God was so inclined, it would have been far less gruesome to prevent the plane wreck entirely. After all, God is supposed to be omnipotent and all that.
The biological function of the entire Earth is difficult to measure in total. Since we cannot possibly visit every high pressure subsurface location on the planet we can only estimate the effects of all human activity on the chemistry that supports us. We seem to think we can just adapt the way bacteria adapt, after all we were able to travel to the Moon and back alive. This may be true but bacteria have been in all the locations of Earth that we can never go to. Bacteria can adapt very rapidly because their cell division is usually far more rapid than more complex organisms like us. With each division comes the possibility of change. Change allows adaptation, even to extremely harsh conditions. We can only have generational babies every 16-20 years or so, allowing much slower adaptation to altered chemistry.
Also, much evolution results in the extermination of the species which were not so lucky. Even if a species survives it might only be due to a small number of lucky individuals to survive any severe changes, much like the survivors of pandemics like flu, small pox or bubonic plague. There are also very bad trade offs in such survival, for instance the sickle cell blood adaptation to malaria parasites.
The faith we have in science to solve all the problems we cause ourselves using science is a whimsy. Science is only a tool like a shovel. A shovel can dig a grave just as easily as a ditch. I intend to use it as a constructive tool for as long as I am around. But I don't pretend that I can prevent the apocalypse or stave off mass starvation of humans and other animals.