CARACAS, Venezuela — An expression of concern by the environmental group Greenpeace about the carbon footprint was marred this week by real footprints — in a fragile, and restricted, landscape near the Nazca lines, ancient man-made designs etched in the Peruvian desert.

The Peruvian authorities said activists from the group damaged a patch of desert when they placed a large sign that promoted renewable energy near a set of lines that form the shape of a giant hummingbird.

The sign was meant to draw the attention of world leaders, reporters and others who were in Lima, the Peruvian capital, for a United Nations summit meeting aimed at reaching an agreement to address climate change. The meeting was scheduled to end Friday but negotiations were expected to continue into Saturday.

Greenpeace issued a statement apologizing for the stunt at the archaeological site, about 225 miles south of Lima. Its international executive director, Kumi Naidoo, flew to Lima, but the Peruvian authorities were seething over the episode, which they said had scarred one of the country’s most treasured national symbols.