Final answer:
Ecotourism refers to ecological factors; it's an environmentally sustainable form of tourism that supports the preservation of natural environments and promotes stewardship.
Therefore, the correct answer is: option 'ecological factors'.
Step-by-step explanation:
The increase in ecotourism, which is tourism aimed at exotic, often threatened natural environments, pertains to ecological factors.
Ecotourism is an international conservation movement that emphasizes experiencing and enjoying natural settings while fostering a commitment to sustainability and minimizing touristic impacts on the environment.
This form of tourism has been developed with the notion of making travel environmentally sustainable while also promoting stewardship for the natural attractions that are visited, such as high traffic sites like the Galapagos Islands or Machu Picchu.
Engaging in ecotourism activities often means directing revenues towards the conservation of these delicate ecosystems, providing job opportunities to local communities, and raising awareness about the importance of protecting both biological and cultural diversity.