Most of my readers know that I'm fundamentally an optimist (see I am an optimist), and that I believe that science and technology (along with human ingenuity) can and will solve most (hopefully all) of our problems caused by technology and the resulting global population growth.
But it won't be easy, or cheap.
Most people seem unaware of the major ecological problems we face, focusing instead on a few relatively minor (but well publicized) potential problems such as Global Warming or loss of biodiversity.
Here are a few more for your consideration.
Loss of topsoil: Globally, current farming techniques results in topsoil being lost to erosion at rates far greater than natural replenishment. Topsoil (the only part of the Earth's regolith that can readily support crops) is being lost at a huge rate, resulting in reduced crop yields and even desertification in some areas. Currently, the recommended solution is to globally convert to no-till farming, which has the problem of requiring greatly increased use of herbicides and insecticides with their attendant and largely unknown long term effects.
Ocean anoxia: The huge influx of topsoil and fertilizer into the oceans is producing larger and more frequent dead zones, where nearly everything larger than a bacteria dies due to lack of oxygen. All of the nutrients lead to bacterial blooms which consume all free oxygen, and while some mobile fish can swim to the surface to gulp oxygenated water or swim out of the region, bottom dwellers and the myriad small critters that comprise the bulk of the food chain have no such ability. They die, and so do other life forms that depend upon them. This process happens to thousands of square miles every year, and the area and event duration is increasing.
Overfishing: The oceans are being depleted of desirable foodstocks are rates far greater than can be maintained. Already, many once common seafoods are becoming rare, and many fisheries are now effectively ocean deserts, completely devoid of large fish. At present, there are two approaches to solve the problem. One is to create huge "no fishing" zones to serve as replenishment stocks for the regions around them. This works in the short run (assuming enforcement by fast, armed ships), but eventually the fish will evolve to avoid fishing zones. The second solution is one that our leaders have done completely backwards. They have established minimum take sizes, where the fisherman is allowed to keep only fish above a certain size. Sounds good at first, as the young fish are allowed to live, feed, and grow. Unfortunately, there is something called evolution. Fish which once grew quickly to a large size (to avoid predation) are now evolving to grow more slowly and to reproduce at a much smaller size (avoiding predation by the most effective ocean predator, us). As a consequence, reproductive success is reduced, and the remaining fish are becoming less and less desirable. The solution? Capture (and eat) medium sized fish, encouraging these species to grow quickly to a large (safe) size and to produce large numbers of offspring to ensure that enough of them escape us to maintain their species. But this will take technology, and leadership.
Falling water tables: Everyone has heard of (or experienced) the relative and growing shortage of fresh water. Many people don't realize how serious the problem has become. Many cities (especially in desert areas but including many water-rich areas such as Orlando, Florida, USA) are pumping fresh water out of the ground at rates much greater than natural replenishment. Eventually the wells will run dry. Going deeper is often not a solution because of salt water, no water, or pollutants such as oil, lead, or arsenic. Along the oceans, pumping fresh water out of the ground encourages salt water incursion, a serious problem. One side effect of excessive ground water pumping is that springs dry up, and rivers that once ran to the ocean now shrivel and disappear. Water wars will result when cities / states / nations consume the fresh water that other downstream cities / states / nations need to survive.
Chemical pollution: To me, the most serious pollution issue is from the long term unanticipated side effects of biochemicals we create and dump into the environment. These include insecticides, herbicides, drugs, hormones, and especially antibiotics. We don't understand the long term effects of insecticides and herbicides; we ignore the possible unintended effects of long exposure to low doses of hormones and many other drugs (traces of which can be detected in many or most municipal water supplies), and we are rapidly breeding (thanks to evolution and the overuse of antibiotics) new bacteria (and likely viruses) which are immune to all known antibiotics. This alone could result in a plague which could destroy most human life.
The growth of cities: We tend to put cities (especially large, growing ones) at the worst possible places: in river valleys, along flatland floodplains, along the mouths of rivers. The same places that are the best possible farmland. We should build them on mountains, in deserts, rocky, hilly terrain, even floating on the oceans. Leave the good farmland to farming. Leave the river deltas for farming and allow the annual floods that replenish their topsoils and ecologies. Our cities continue to grow at alarming rates, covering the surrounding land with buildings and asphalt. And polluting or burying the former topsoil in the process.
Are there long term solutions? My favorite is to move humanity off of Planet Earth and into space habitats. See Colonizing the Solar System and Population Unlimited. Unfortunately, I expect that humanity will tend to continue to exploit the Earth in ever greater degree until the point is reached where most of the population will abruptly die. And then the survivors just might be smarter and do it right the next time. That, my friend, is evolution in action.