Necessity to Assess the Sustainability of Sensitive Ecosystems: A Comprehensive Review of Tourism Pressures and the Travel Cost Method

Sensitive ecosystems play a major role in the future of the environment, economy, and society, as they affect and mitigate natural hazards, provide food, energy, and medicinal resources, and job opportunities, as well as cultural and recreational services. Meanwhile, the rapidly growing nature-based tourism sector is applying unsustainable pressures on such ecosystems, prioritizing the assessment of their sustainability, i.e., environmental, economic, and social functionality. To ensure long-term development and conservation, benefits from the natural capital must be valued and included in its management plan. The travel cost method (TCM), although heavily exploited in research, exhibits application challenges and methodological weaknesses. This paper seeks to comprehensively present the most recent applications of TCM, focusing on aquatic ecosystems that serve as tourist destinations, whereupon research gaps are identified, ultimately providing insights for future directions in the field. Quantifying the economic worth of sensitive ecosystems is a prerequisite to address issues, such as overexploitation, pollution, and climate change, so these problems can be alleviated in the long-run. In parallel, the critical long-term double effect of fair entrance fees is recognized, which not only motivate visitation by securing accessibility but also guarantee adequate financial resources to protect and maintain the ecosystems’ integrity.