Panelists exchanged comments, which were kept anonymous to maintain survey neutrality during the rating process. These lightly edited excerpts offer a glimpse of panelists' varied points of view and the reasoning behind each score. They are not the views of the National Geographic Society.

Argentina/Brazil: Iguazú Falls
Score: 61

"A small island of preserved rain forest in vastness of agricultural land almost bereft of wildlife and trees. Mass tourism, no feeling of local culture, shop-window ecology."

"Spectacular aesthetic appeal, some improvements in tourism have been made, much more needed."

"Since revitalization of the Brazilian National Park, this site has much improved."

"The national parks on both the Brazilian and Argentine sides need more transboundary cooperation. The natural aesthetic appeal continues to be a major draw. There is plenty of room for improving the interpretation of the park's biodiversity."

Argentina: Península Valdés
Score: 66

"Well-managed and worth the trip, this maritime Serengeti is a star wildlife site. Lodging was bleak a decade ago, but the new wave of ecolodges is very popular among Argentine planners."

"Key limits are water availability and fragility of some wildlife. It is now a cruise ship destination for round the Horn cruises—significantly enlarging day visits on some days."

"Nearing 100,000 visitors per year, this fragile peninsula is approaching a tipping point. Careful planning of infrastructure and gateway community development to manage the inevitable surge of interest will be key going forward."