Consequences of De-evolution
De-extinction is the process of bring a species back from being extinct. Although this has not been completely accomplished yet for more than 7 minutes, here the process that is currently being tested and experimented with:
Find frozen or preserved DNA of the extinct animal
Map the genome of the extinct animal
Find the living animal that is closest to the extinct animal and determine the differences in their genomes
Change extinct animals genome accordingly
Artificially inseminate a surrogate mother of the currently living species with the old genome.
The mother will then reproduce and create a hybrid
Two hybrids will then reproduce with each other and therefore recreate a purebred of that species
If there is no possibility of a surrogate mother due to the extinct animal being too big or not close enough to any living species that could be used., scientists think it may be possible to create an artificial womb.
Throughout the years since these animals went extinct other species have adapted in order to fill their niche or advance it, therefore if you brought back those animals it could cause another group animals to go extinct. Also, it might add an extra predator to other species therefore causing them to die out as well.
For example bees are a very important factor in the world today, without them many types of plants - and therefore animals - would go extinct. Already bees have many predators who aim to eat the honey inside their hives, for example birds, small mammals, reptiles and other insects. Certain animals, if revived, could add another predator to the food chain that they are not adapted to fight of and avoid and therefore cause them to go extinct. This could then lead to many more problems in the world.
A New World
Not to mention that many environments themselves have changed and therefore many animals would not have enough resources or space to survive. For example arctic animals like the wolly mammoth would be added into a fastly evaporating climate and would struggle to survive with the other endangered animals like the polar bears.