Shifting baseline

Shifting baseline means that our idea of what is normal changes over time. It's like when you move to a new house, the first day it feels different to what you are used to, but after you've lived there for a while, it starts to feel normal.

Shifting baseline can also happen with animals and their environment. For example, if there used to be lots of fish in a river, but over time there are fewer and fewer fish, it can seem normal to us - even though the number of fish is much lower than it used to be.