> It made me really sad to think about the fact that we'll probably see mass-extinction events (for animals, etc.) in the near future or at least within my lifetime

It's generally agreed that we are already living within a mass extinction event[0]

[0] https://en.wikipedia.org/wiki/Anthropocene#Biodiversity "Humankind has entered what is sometimes called the Earth's sixth major extinction. Most experts agree that human activities have accelerated the rate of species extinction.The exact rate remains controversial – perhaps 100 to 1000 times the normal background rate of extinction"