We really don't.
Stick with it and watch the second film.... you will throw up.
I was watching the Michael Palin Himalayan thing, Bangladesh, the other night and you could almost smell and taste the shit coming through the screen. It was truly disgusting - 162 million of them in and area 3/4 the size of Britain, and still they breed. And these are not isolated cases, they are all over the globe, and they keep on coming thicker and faster - habitats destroyed so that we can "live", make a few bob, own a phone, use an app, throw away a few times worn T-shirt.
Humanity: the most intelligent and most stupid organism in the Universe.