Biogeography: Distribution of wildlife

Distribution of wildlife

Animals are spread unevenly over the Earth because of climate, vegetation, barriers (oceans, mountains, deserts) and the long history of moving continents. Alfred Russel Wallace divided the world into zoogeographic realms: Palaearctic (Europe and north Asia), Nearctic (North America), Neotropical (South and Central America), Ethiopian or Afrotropical (Africa south of the Sahara), Oriental (South and South-East Asia, including most of India) and Australian. The Wallace Line, a deep-water channel between Bali and Lombok and between Borneo and Sulawesi, separates Asian from Australian animals.

Prelims 2023 offered Statement-I: Marsupials are not naturally found in India. Correct: marsupials (pouched mammals such as kangaroos and koalas) are found naturally in Australia, New Guinea and the Americas (opossums). Statement-II, that they can thrive only in montane grasslands with no predators, is wrong (option c). Australia’s marsupials survived because the continent split off before placental mammals reached it.

India sits where three realms meet (Oriental, Palaearctic in the high Himalaya, and Ethiopian in the dry west), which is one reason it is a megadiverse country, with about 7–8% of the world’s recorded species on 2.4% of its land. It is the only country with both lions and tigers in the wild.

Altitude gives zones too. Prelims 2019 asked which one of the following National Parks lies completely in the temperate alpine zone: the Valley of Flowers (option d); Manas, Namdapha and Neora Valley include lower, tropical or subtropical forests. Mains 2019 asked: How can the mountain ecosystem be restored from the negative impact of development initiatives and tourism? Mains 2019 Carrying-capacity limits for pilgrims and tourists, strict slope and building rules, scientific road cutting with slope stabilisation, eco-sensitive zones, afforestation with native species, solid-waste management, community-run homestays, and early-warning systems for floods and landslides, as the Joshimath subsidence and Kedarnath flood showed.