Los Petenes biosphere reserve, Biosphere reserve in Campeche, Mexico

Los Petenes Biosphere Reserve is a 282,858-hectare protected area on the northern coast of Campeche, Mexico, spanning four municipalities and extending 12 nautical miles into the Gulf of Mexico. It is a low, karstic coastal plain with no surface river network, where freshwater from the peninsula's aquifer emerges as springs and cenotes, mixing with saltwater to form saline marshes, lagoons, and mangrove wetlands. The photograph shows a still, dark green waterway lined by a dense wall of broadleaf trees and shrubs, with a narrow band of pale yellow-green reeds at the water's edge and scattered round lily pads floating in the foreground.

The area was designated a biosphere reserve in 1999 after conservation efforts drew attention to its ecological and archaeological value. Among the sites protected is Isla Jaina, a Maya island used as a burial ground along the coast.

The name "petenes" comes from a Maya term meaning 'flat fields beside the sea like islets', describing the vegetation islands around freshwater springs. The reserve is a Ramsar wetland of international importance since 2 February 2004, and its 282,858 ha make it the largest protected area in the Gulf of Mexico.

The months between October and May bring cooler and drier conditions, which make moving through the wetlands easier. A guide is strongly recommended since many paths through the mangroves and lagoons are hard to follow without local knowledge.

The name comes from the Maya term for 'flat fields by the sea like islets', describing islands of tall trees fed by freshwater springs that rise through the saltwater marsh. The reserve protects the largest such formation in the Gulf of Mexico, and its federal decree of 24 May 1999 set the protected area at 282,858 hectares.