Somewhere around you, you can spot a bush. It is very small, but very interesting as well.
You see that many species are growing together here to form one little bush, the species with thorns protect the species without thorns against grazing animals when they are young. You can see this in the picture below, which was also taken in the floodplains. When they grow older and get sufficient bark, these thornless trees do not need protection anymore and can form solitary trees in the landscape when they shade out the thorny scrub beneath them.

This is just one example of a natural interaction between trees and animals that forms a park-like landscape. The theory behind these interactions is also the foundation for the introduction of grazers in the Oostvaardersplassen area of which you might have heard. Frans Vera is the main ecologist behind this thinking. His ideas of wilder, more robust nature changed nature conservation in the Netherlands decades ago.
Now have a look at this bush, which species do you recognize? Are they thorny or not?