Visitors to the Galápagos Islands will likely pay an increased park fee starting next year, a decision that reflects growing concerns that skyrocketing tourism on the Ecuadorean archipelago is harming its fragile and unique ecosystem.

Visitors currently pay a $100 fee to the Galápagos National Park, with mainland Ecuadoreans paying $6. Last month, Ecuador’s ministries of tourism, environment and agriculture proposed doubling costs to $200 for those visiting the islands who also spend at least three nights in mainland Ecuador and quadrupling the fee to $400 to visit Galápagos and spend only one or two nights on the mainland.

The exact prices, start date and how authorities confirm itineraries will be decided by December 31, said Daniela Tamayo Córdova, of the Galápagos Government Council, the municipal body that manages the islands.

“The entrance fee has not increased in 20 years, and costs in Galápagos and Ecuador have risen over this time,” Ms. Córdova said. “The increased income will be used to improve sustainability, tourist experiences, and conservation and management.”