<P> Other major problems facing the canal system is the damage by introduced species and disease destroying native ones . Water lilies were introduced to the canals from Brazil in the 1940s . Since then, they have become a serious problem as their overgrowth depletes minerals and oxygen from the water . Up to 400 tons of the plant has been extracted from the canals monthly . In 2006, a Brazilian insect (Anthonomus grandis) was introduced to the canals to help control the plant . However, some need to be maintained because the axolotls are using them for reproduction purposes . Introduced species include carp and tilapia, which were introduced in the 1960s . However, these have been very detrimental to the native ecosystem, especially the axolotl, whose eggs they eat . Despite tons of the fish being caught in the canals, they are still a serious problem . Another major problem is the loss of trees, especially junipers in the ecological zone . Over sixty percent of the area is considered to be serious deforested and eighty percent of the junipers have the parasitic plant mistletoe . </P> <P> Since being declared a World Heritage Site, there have been attempts to rescue the canal system . The first major effort occurred between 1989 and 1994, which was called the "Rescate Ecológico ." It had the goal of constructing a large artificial lake for tourism and sports covering 360 hectares, ten times the size of the lake in Chapultepec Park . These would be divided into two parts called the Ciénega Grande and Ciénega Chica on the side of the Periférico Sur . It would also include the creation of a chinampa zone, and areas for culture and commerce and elevated buildings over the two sides of the Periférico Sur similar to those in the San Jerónimo area . However, this plan was stopped by agricultural communities in the area, which have a long history of defending their rights . However, since then, the area has been urbanized . It was replaced by a much smaller lake, with ecological area and plant market . In 2008, borough authorities began a reforestation program over 5,000 hectares of chinampas and forested areas at a cost of 20 million pesos . This program includes the cutting of non native species such as eucalyptus and certain pines and cedars to eradicate plagues associated with them . However, residents near forests such as in Nativitas oppose the cutting of healthy trees . These are to be replaced by native species, especially junipers in the chinampa areas . However, it is still estimated that because of the continuance of urban sprawl, the remaining canals and protected land will disappear within fifty years . </P> <P> The canals of Lake Xochimilco were initially created along with artificial agricultural plots called chinampas . Chinampas were invented by the pre-Hispanic peoples of the region around 1,000 year ago as a way to increase agricultural production . On the shallow waters of the lakes, rafts were constructed of juniper branches . Onto these rafts floating on the water, lakebed mud and soil were heaped and crops planted . These rafts, tied to juniper trees, would eventually sink and a new one be built to replace it . Over time, these sunken rafts would form square or rectangular islands, held in place in part by the juniper trees . As these chinampa islands propagated, areas of the lake were reduced to canals . These "floating gardens" were an important part of the economy of the Aztec Empire by the time the Spanish arrived . Today, only about 5,000 chinampas, all affixed to the lake bottom, still exist in their original form, surrounded by canals and used for agriculture . The rest have become solid ground and urbanized . In the center of Xochimilco, there are about 200 chinampas, covering an area of 1,800 hectares . However, one reason the number has decreased is that smaller chinampas have been combined to create larger ones . While there are still those who maintain chinampas traditionally, and use them for agriculture, the chinampa culture is fading in the borough with many being urbanized, and being turned into soccer fields, and sites for housing and businesses . The deterioration of many of these chinampas can be seen as their edges erode into the dark, polluted water of the canals . The most deteriorated chinampas are located in the communities of Santa María Nativitas, Santa Cruz Acalpixca, San Gregoria Atlapulco and Ejido de Xochimilco . Together, these have a total of thirty eight illegal settlements . To repair a number of chinampas, the borough along with federal authorities, has reinforced forty two km of shoreline, of the 360 km (220 mi) that exist in the lake area . This involves the planting of juniper trees and the sinking of tezontle pylons into the lakebed . These remaining chinampas are part of the Xochimilco World Heritage Site . Have since changed use and become residences and businesses . Those that remain agricultural are mostly used as nurseries, growing ornamental plants such as bougainvilleas, cactuses, dahlias, day lilies, and even bonsai . As they can produce up to eight times the amount of conventional land, they are still an important part of the borough's agricultural production . There have been various attempts to save the remaining chinampas, including their cataloguing by UNESCO, UAM and INAH in 2005, and various reforestation efforts, especially of juniper trees . </P> <P> About an hour long canal ride from an embarcadero, pier, lies Isla de las Muñecas, or the Island of the Dolls . It is the best - known chinampa, or floating garden, in Xochimilco . It belonged to a man named Don Julián Santana Barrera, a native of the La Asunción neighborhood . Santana Barrera was a loner, who was rarely seen in most of Xochimilco . According to the legend, SantanaBarrera discovered a little girl drowned in mysterious circumstances in the canals . He also found a doll floating nearby and, assuming it belonged to the deceased girl, hung it from a tree as a sign of respect . After this, he began to hear whispers, footsteps, and anguished wails in the darkness even though his hut--hidden deep inside the woods of Xochimilco--was miles away from civilization . Driven by fear, he spent the next fifty years hanging more and more dolls, some missing body parts, all over the island in an attempt to appease what he believed to be the drowned girl's spirit . After Barrera's death in 2001--his body reportedly found in the exact spot where he found the girl's body fifty years before--the area became a popular tourist attraction where visitors bring more dolls . The locals describe it as "charmed"--not haunted--even though travelers claim the dolls whisper to them . Professional photographer Cindy Vasko visited the nightmarish island in 2015 and described it as the "creepiest place (she has) ever visited". The excursion began through maze - like canals, surrounded by lush greenery and beautiful singing birds, but soon her boat was slowed down by a swarm of lily pads and the canal fell ominously silent . She told MailOnline: "At the end of the journey, the trajinera turned along a bend in the waterway and I was struck by a surreal vision of hundreds, maybe thousands, of dolls hanging from trees on the tiny island ." The dolls are still on the island, which is accessible by boat . The island was featured on the Travel Channel show Ghost Adventures and the Amazon Prime show Lore (TV series). </P>

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