The decline of biodiversity at the hands of modern humans likely started even before the last Ice Ages. Recently some scientists have proposed a scenario called "Pleistocene re-wilding," which offers an optimistic agenda for 21st-century conservation to bring back animals that disappeared from North America 13,000 years ago.
What could be the pros and cons of populating the area with animals such as lions, cheetahs, hyenas, elephants, camels, etc.? Would that help bring back some of the lost biodiversity?
To the second question "Would it bring back some of the lost biodiversity?" ...perhaps, or perhaps not. The dynamic balance between organisms in an ecosystem is something that takes centuries or more to develop - and something that is in a constant state of flux. Such assemblages of life are constantly changing in subtle ways (hybridization, mutation, and genetic drift), and occasionally in more fundamental ways as even extinctions occur in nature.
So to directly address the pros and cons aspect: yes, in the short term opening a zoo to the natural world (which seems ...
Discusses the potentials of re-wilding an environment with new, non-native, species