Hmmm, are you sure that most people really care about the survival of humanity in the abstract? I mean, humans are obviously wrecking the biosphere and polluting earth severely, but people keep right on burning fossil fuels when alternatives are available. Also, human overpopulation is a major threat to earth's survival, but few support birth control.

A lot of what you're saying is hand-waving that isn't supported by the facts. The human birthrate has dropped considerably in the past 60 years. In several places (most of Western Europe, Russia, Japan), the birth rate is far below the replacement rate. If not of immigration, their populations would be declining. Even in most of the poorest places on Earth, the birthrate has dropped considerably.

From this source:

The world birthrate is estimated to have been around 37 per 1,000 in the early 1950s, and it is estimated at 21 per 1,000 in 2000. Since the 1950s, the birthrate for all Europe is estimated to have fallen from 21 to 10 per 1,000 (in the United Kingdom, the birth rate fell from 16 to 11 per 1,000); in the United States from 24 to 14, Canada 28 to 11, Australia 23 to 13, and New Zealand 26 to 15 per 1,000; in Latin America to have dropped from 42 to 22 per 1,000; in Asia to have halved from 43 to 21 per 1,000 (in the People's Republic of China alone, the birth rate fell from 44 to 16 per 1,000); and in sub-Saharan Africa to have declined from 48 to 41 per 1,000. A well-conceived public health strategy is likely to include provision of a range of contraceptive and other family planning services as part of broad based health interventions designed to attain sustainable economic as well as social improvements.

As for pollution, people in many impoverished countries admittedly worry far more about feeding their families than cleaning up the environment. My wife is from one of those countries so I have some info on the matter. As for industrialized nations, those with market based economies such as the US, Canada, Western Europe and Australia have developed and implemented many technologies to clean up the environment. I turn 51 next month. When I was growing up in the 1960s, about the only cars that had any form of emission controls were those sold in California. I've read (but don't have a source to confirm) that cars back them released about 400 times as much pollution per mile driven as modern cars. Comparing the technology then to today, it isn't hard to believe this is true. Back then, it was common for factories and communities to dump untreated waste into rivers. That doesn't happen any more or not for long. Better land fills, far better sewage treatment, and pollution control are the order of the day.

Admittedly, pollution control is much less of an issue in places with a demand economy such as China and the former Soviet Union. They're heavily polluted and will likely be for some time to come.

As for fossil fuels, replacements are available for some of it but only for a fraction of the energy needed to support a modern economy. As the economies improve in heavily populated places like China and India, their desire for an improved standard of living (completely understandable, IMO) will lead to an increase demand for energy. At the same time, India is perhaps the world leader in the technology of using compressed air to power cars. It's an interesting concept. China is active in developing advanced battery technology and has a fledgling electric car development effort underway. The US is offering cleaner power plant technology to China and India. If adopted, that will go a long way towards reducing their pollution.