ISSUES

De-extinction may change the priorities of other fields. Instead of funding for conservation of endangered species or focusing on medical researches, it may be more focused on de-extinction.
It would reduce the amount of effort in the Endangered Species Act since more is focused towards executing de-extinction.

The resurrected species could be a carrier for a fatal disease or an unintentional threat to current species or ecosystems.
It could potentially be invasive to other species or ecosystems, disrupting the balance of the food chain.
If the resurrected individuals are clones, current disease may even wipe out the whole population because of identical DNA.
Where should the resurrected species be placed if they are re-introduced to our world? It is unsure where exactly these species would live.

Millions of money would be used to bring back a few species, but it does not compensate for the millions of lives lost due to human activity.
The cost of failure could be more than successful trials. Extracting the DNA is easy, but for the fetus to develop in a surrogate or artificially is difficult.
It can shift the focus of money on the technology of de-extinction rather than focusing on conserving current endangered species.

It is unethical to animal welfare. Animals, like us, are individuals with feelings and should not suffer in human's experiments with sciences.
De-extinction is not animal conservation. If one of the main purposes is to bring back the dead, science should focus on helping endangered species. It ignores the current mass-extinction problem to many species.
If de-extinction is successful, scientists may take it too far and resurrect other species that can potentially be dangerous to the environment due to unknown factors.
There is no clear evidence that even if the extinct animals are brought back, they would act the same as they used to.

Other

Political

Environmental

Economic

DE-EXTINCTION