If you are an Ecologist, you are able to reintroduce species, crops and plants into areas of your nation...for a small fee of course!
Ecologist clan member's options
You can go visit any Clan Member within your Nation and choose the option 'Manage this territory' to see what monsters, crops, ect. are available to you. If a certain species is extinct, you can bring that species back to life by paying a fee to the Clan Member in order to bring that species back.
Protecting or reinstating species
To be able to pay the fee, the Ecologist will have to talk to the current Treasurer in order for them to have sufficient funds to carry out actions such as protecting a species and bringing one back from extinction.