Xochimilco lies 28 km south of Mexico City. Its network of canals and artificial islands are the efforts of the Aztec people built on a habitat in the midst of an unfavorable environment. It is said these islands had very high crop yields with up to 7 crops a year. The artificial and floating island called chinampas’ transportation is the colorful non-motorized wooden boats- “trajineras”, which sails through the 170 km. canals. Trees such as“āhuexōtl" or "āhuēhuētl" is an important part of the ecosystem, planted at the corners to secure the chinampa and act as wind breakers. The ecological reserve Xochimilco was added to World Heritage Site in 1987, but the area is facing severe problems, posed by development pressures, changes to land-use, abandonment and contamination.