Natural succession is the way that the ecology changes over time. The textbooks usually take it from an open field or a pond to a forest. You can see natural succession in Warnimont Park in Cudahy. Around 1970, the park was mostly grass. I started to run down there about that time. I remember there were lots of thirteen-lined ground squirrels. They stopped mowing and soon wildflowers moved in, followed by pioneer trees Today, large parts are young forest. I have watched the evolution over the past 45 years.
I do wonder a bit about the future here. In SE Wisconsin, green ash are among the most important pioneer trees. With the emerald ash borer, I wonder what will happen.
The first picture is still mostly meadow I think they cut it occasionally. The second shows the running/bike path with young forest. That used to be all grass. Next is a grove of black walnut. They planted those in the 1980s. Last is one of the bluffs. If you look closely, you will see all the dragon flies. The sky was full of them. They are generally beneficial.