Am meant to understand that bioindicators are simply living organism that gives us an idea of the general health state of an ecosystem.
Drawing from the definition above and if there were actually higher species living amongst us, humans will definitely be bioindicators, biologically indicating the trails of destructions we've left in every of our paths around the globe.
This is going to sound crazy and a lot of people will disagree, but I personally believe in the presence of higher intelligent species on earth. Maybe not human or earth like creatures, but extraterrestrial scouts, coming in and out of the planet to study us. If that be the case, then our very existence and how much we've taken and keep taking from nature leading to increasing depleting resources will most definitely count as a major bioindicator.