The Tragedy of the Commons.
The tragedy of the commons typically starts with a common good or shared resource that is free for all, as an example here we have 4 farmers each with one (1) cow, the shared resource is the pasture and each cow grazes just a little out of this resource, this system can usually be considered stable or balanced.
"The commons" originates from the colloqial term of unregulated grazing land back in 1800’s in the British Isles.
Trouble starts when one farmer figures out that there is enough grazing land for at least one more cow, ( conveniently his extra cow ), this makes economic sense since he can take advantage of the free food for his cow and earn more money.
The result is insignificant at first, the system can easily handle the extra cow.