Back when I was in elementary school, I remember the monarch butterfly migration that happened in California. You could stand outside and witness dozens of monarchs passing through the school yard. They were everywhere and it was beautiful.
Unfortunately, those butterflies are now gone. You can no longer stand outside in the Bay Area and see monarchs fluttering by on their migration. Those butterflies, for the most part, no longer exist. They were destroyed through a combination of habitat destruction and widespread chemical usage.
Thanks to the mindless American drive towards unfettered capitalism and growth, this awe inspiring sight of nature can only be viewed on YouTube or if you have the time and money to travel down to Mexico. Creatures that existed for thousands of years before humans arrived in California are now gone and may never come back.