This article describes and discusses an innovative index-based environmental protection mechanism involving both tourists and local firms of a given region. The public administration offers tourists (non-polluting firms) the possibility of being reimbursed if the environmental quality in the region turns out to be below (above) a given threshold level. Since the two kinds of reimbursements (to visitors and firms) are linked to the same ecological indicator, they will tend to compensate each other, so that the mechanism could be implemented without incurring any cost for the public administration. The article identifies potential difficulties that may arise in its application and proposes corresponding solutions to address them.