Canals and open areas not coverted to agricultural production teemed with fish and other aquatic wildlife. These areas also attracted many bird species, valued in the past more for their taste and plumage than simply their presence. Of course, the lakes that surrounded Tenochitlan were drained long ago to alleviate flooding. Furthermore, the many freshwater springs which once fed Lake Xochimilco have been successively diverted to provide drinking water supply for Mexico City. Ironically, the chinampas were saved from certain extinction by substituting streams of treated sewage and industrial waste waters for the spring flow.
Water levels fluctuate widely and unpredictably.
Moreover, phosphates and other contaminants introduced from the treatment plants complicate the agricultural use of the chinampas considerably. Because of inadequate water supply, urban expansion and economic pressures, many chinampa farmers have decided to switch from subsistence or vegetable production to cultivation of flowers and plants for sale throughout Mexico. Others have simply abandoned their fields. They now use them to grow forage for a few cows, or they fill in the canals and build houses. While you may have heard that the chinampas are extinct, you can find them behind the canals frequented by the tourist trajineras.