There is a central database, and it is used in research regarding climate change, and as a way to monitor the changing environmental conditions,
As a database, the blockchain would totally work and one of the reasons I add these posts to Hive is not just to share knowledge, but because I know the records/posts I make can't be removed)
It would take a huge shift in mainstream adoption for the various moth spotters to start though, and it would need to be more user friendly (or maybe like 2nd layer app type thing), but who knows what the future will bring, and the potential possibilities too