There have been five mass extinctions of life before. The most famous of which wiped out the dinosaurs. With the rate of extinction of species it is clear we are currently going through a sixth mass extinction. This is caused by climate change and human wrecking of animal habitats. And it will if not halted, lead to the extinction of humans.
It is not going to happen over night, this is not a made for TV disaster movie. But as we ruin more animal habitats and climate change gets worse, we will make living environments for humans worse. In Avery short space of time we have seen decreasing world wide fertility thought to be caused by plastics, much more frequent occurrences of dangerous weather, rising sea levels that are reclaiming land from humans, and decreasing levels of animals that are needed for human survival such as bees.