Roberto Altamirano, left, and Leonardo Sastre submerge a cage of axolotl salamanders into an experimental canal for a project geared to recover their population in Lake Xochimilco, in Xochimilco, Mexico, Aug. 20, 2012. The decline of the axolotl in the wild has been precipitous and its extinction would extinguish one of the few natural links Mexicans still have with the city that the Aztecs built. (Rodrigo Cruz/The New York Times)
