Alligators! Being raised in the swamps of southern Louisiana I spent many years hiking, exploring and playing in the swamps. Never saw an alligator. In the 1980s I spent 10 years in the Honey Island swamps training my coon dogs and just occasionally saw an alligator. I would hunt alone walking miles deep into the swamp with my dogs with no fears. Now, in the 2000s I have them in the ditch in front of my house, across the levee in the Mississippi River, and occasionally under my house. You could not pay me enough now to go in the Honey Island swamps by myself. They are everywhere.
Thousands are now caught every alligator hunting season and fried alligator are on the menu of many New Orleans restaurants. Also, nutrias, which do millions of dollars of damage to our levees each year but are only semi-controlled by the alligator population. At least the pelicans are finally back due to DDT being banned and I saw my first bald eagle about 2001 in a nest in a tree directly across the levee from my house. Also, the coyotes have taken over everywhere the Mississippi flows. Forget rabbit hunting because the coyotes got them all. And I can't play with ladybugs anymore because the only here now are the Chinese ones and they bite.
And did I mention hurricanes? We had Betsy in 1965 and not another one until Katrina in 2005, 40 years later, now they are a yearly visitor. Makes me wonder what will be around 50 more years from now.