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.