Threatened wonders of the natural world such as Australia's Great Barrier Reef could be in greater peril because of "last chance" tourists flocking to visit, experts say.

To investigate the phenomenon, scientists surveyed more than 230 visitors to the reef last year.

"Last chance tourists" (LCTs) were found to be older, environmentally conscious individuals - mostly women - who had travelled long distances.

They were also more likely than other kinds of tourists to be concerned about the health of the reef, especially the way it was being affected by climate change and bleaching.

Researchers Annah Piggott-McKellar and Karen McNamara, from the University of Queensland, wrote in the Journal of Sustainable Tourism: "This finding was of interest, as it emphasises the paradox involved in LCT, in that tourists are travelling greater distances to view the destination that is in danger, contributing higher levels of emissions and thus exacerbating the impacts of climate change."

Population pressure and activities associated with access also contributed to the deterioration of sites, they said. As a site became more endangered, its status as an LCT destination was raised further.

The people surveyed had only a "moderate to low" concern about the impact of the tourist industry on the reef and did not consider their own travel to be damaging, the researchers found.