Releasing captive animals, wether originally wild or captive bred can be diasterous for wildlife! The problemm is not that the liberated animal(s) may die. That is inconsequential. We have been taught all this crap about how important individuals are...they are not...not when it comes to dealing with wildlife. Populations are what really matter.
A released captive pet can introduce disease that can be devastating to populations that have never encountered it before. Remember what the Europeans did to the American Indians of the eastern US? The same could happen to turtles if a turle disease from...say Asia...is released into the US with freed pet. This may be the source of the respitory infections afflicting North American tortoises.
If more than one specimen is released in a favorable habitat they may establish a new population. Introduced species can drive native species to extinction. Check your state wildlife agency's website. There is more than one introduced species raising Hell where you live.
Even releasing native species from other populations can have adverse affects. Eastern painted turtles from Florida released in New England will likely mate with some native individuals. They will pass on their warm winter genes in a cold winter population. This drops the genetic fitness of the New England population. This can also pollute unique natural gene pools that have been reproductively isolated for thousands of years. This pollution will result in the loss of certain genes from that species genome.
The best thing that can happen to a released pet is that it very quickly dies!
Remember: In all of these scenareos we are the bad guys!
Never release pets! If you catch an animal and only want to hold it for a short time (maybe to photograph it)follow a rules rules to avoid the above diasters.
1 NEVER expose it to other captive reptiles or birds. Birds are reptiles and can carry similar diseases. Keep it as far away as possible and always handle it BEFORE handling your long term captives.
2 ALWAYS release it EXACTLY where you found it...not in a "better" place.
3 Check local and federal laws. Be sure you are not breaking them.