1) Pollution/poisoning of our food and water sources - occurring on a global scale, in our oceans, on land, caused by industrial pollution, nuclear disaster (IE - Chernobyl), poisons sprayed onto crops, plastics, GMOs, antibiotics, inhumane mass production of 'meat' sources, etc.
This is the cause of the rise in heart disease, cancer, autism, obesity in children becoming an epidemic problem, etc.
2) Overpopulation - more people means more pollution, the world's food resources are being exhausted, energy resources are being tapped out, the escalating population growth will lead to our ultimate demise... civilization as we know it will collapse, as technology increases in ability, making human labor obsolete, there will literally be billions of people on the planet without any real means of supporting themselves through economic productivity.
3) Non-state Nuclear war - because Nuclear devices have become common place throughout the world, including unstable nations such as North Korea, it is inevitable that a 'dirty bomb' will eventually fall into the hands of a terrorist organization and be used in a highly populated city, most likely in Europe or Israel, but possibly NY being the easiest target as the device could be transported by freight ship, cruise ship, any type of ship and not be detected before detonation.
4) Non-nation global dominance of corporations - corporations are not nations, and do not answer to, or for, the benefits of society or the people, they exist purely to make profit, even at the cost of humanity's best interests. The age we are entering into, a corporate dominated world where corporations and banks have more power and control than nation-states, will greatly advance the dire problems mentioned in the above three issues. In fact I would say they are the current causes of these problems now.
5) The destruction of societal and cultural norms - when there are no standards, there are no acceptable norms to be adhered to, when it is not correct to praise those who succeed, or win, because in turn you hurt those who do not succeed, or lose. When the sexual molestation and abuse of innocent children becomes an acceptable part of society, and speaking out against such abhorrent acts becomes a 'hate crime', you are living in a society that no longer has any worthwhile values, where corruption and power rules, and sadly this is the direction our nation is currently headed.
I don't have room for the next five, but those are bad enough.