While walking through the zoo next time, look closely at those ominous signs listing animals that are endangered.  The numbers are growing. The 100-acre San Diego Zoo is dedicated to the conservation of endangered species and their habitats, and is home to more than 4,000 rare and endangered animals representing more than 800 species and subspecies. Increasingly, zoos are faced with the dilemma of finding solutions to changing ecosystems, those dynamic interactions between plants, animals and microorganisms and their environment working together as a functional unit.  Ecosystems will fail if they do not remain in balance, and that could be fatal for many species.  In the last decade alone, 10 species were eliminated. Rick Swartz, ambassador of the San Diego Zoo and Wild Animal Park, explains that animals are being crowded out of existence, relative to human behavior. The problems include poaching, farming and town expansions, pollution, habitat and climate changes. “These are issues that affect every living being on this planet,” he said.  “Over the decades, man has been a little less considerate when it comes to expanding and construction.”  A national research report indicates that about 5,000 species of animals are facing extinction. Some are considered on the brink of disappearing and possibly beyond all hope of salvation regardless of efforts to save them.  “In some cases, like the tiger and leopard, it’s a matter of encouraging the population of their prey,” Swartz said.  “But human population is multiplying greatly and the destruction of tropical rain forests and other habitat is happening at a frightening rate.”  Swartz said the world has seen a lot of changes in the ecosystem in the last six years, particularly in bird and plant life.  “It’s a big concern whether we’re talking about a bird or frog,” he said. “We must do something now.” There is a collaborative effort among zoos with breeding programs, and conservation organizations are reaching out for partnerships with the world’s wildlife parks, constantly looking for alternatives for natural migration. “We have established [a program] now in Botswana in hopes of finding some solutions,” Swartz added. The San Diego Zoo established the Zoological Society of San Diego’s Center for Conservation and Research for Endangered Species, and the program boasts the largest zoo-based multidisciplinary research team in the world. One of San Diego Zoo’s most ambitious habitats is Joan B. Kroc’s Monkey Trails and Forest. It serves as the naturalistic home to some of the world’s most exotic and endangered wildlife, housing more than 30 species of African and Asian birds, mammals, reptiles and amphibians. Meanwhile, the two-year-old $44 million Elephant Odyssey’s seven-acre habitat features Asian and African elephants, a California condor, sloths, snakes and rodents. Swartz said the current situation faced by endangered species needs to be remedied soon. “There will be an unstable population if [endangered species’] habitats are not improved,” said Swartz. “The problems are multifaceted, and we must find what the animals need, namely, space.”