>>523876This
We're probably standing at the edge of a precipice that could lead to another mass extinction similar to the Big Five. Humans need to radically change the way we interact with the environment or we could get to a point where the Earth loses 75% of species globally. If you're unconvinced search "Has the Earth’s sixth mass extinction
already arrived?" on Google scholar. It is a rather interesting paper that presents decent data to support.
By releasing lots of carbon dioxide and sulfur dioxide into the air, humans are causing not only a green house effect but also acidifying the Earth's oceans. Acidification (drop in pH) causes the calcification equation to shift towards the dissolving side. Which means many forms of ocean life (corals, forams, certain planktons, etc) will find it harder to solidify calcium from the water. Many of these calcium secreting organisms form the base of the trophic levels that exist in the ocean. If they were to have a mass die off then there would be a cascading effect as you move up the trophic levels.
There's also the business of habitat loss. The quickest way to drive an organism to extinction is ruining the habitat it is most suited to be in.