Of course Climates change. There have been warmer periods and colder periods. Say a society flourishes during a warm period,agriculture goes well. Akin to having vine plantations up north in England or even Sweden. But now enters a cold period.

What happens to those resources that allowed a society to thrive? The capacity is diminished and so a society build on this temporary warmer climate, begins to collapse.

However, in our time, given the global scope of agriculture, there is no need to be concerned about that.

The other items this video point towards, are way more interesting. And as Durant noted: the collapse of the family unit was the core around the collapse of the Roman Empire.

There are more issues surrounding this matter. Such as a loss of confidence and trust in our fellow being to keep his word. Our society, based on trust, is being eroded by many things, not the least promoted invasion of aliens.