Extinction of species is part of the natural lifecycle of planet Earth. In Earth’s 4.5-billion-year-old history, over 90 per cent of the organisms are extinct.
But in all the major eons, with ice ages and extinctions, no species has ever impacted the climate as much as Humans have. Humans have contributed to the natural cycle accelerating extinction due to activities causing habitat loss, climate change, invasive species, disease, overfishing, and hunting.
In fact, we humans are like mice building a giant mousetrap for ourselves.
- Today, scores of species deplete in numbers. Scientific estimates opine that over 20,000 species of flora and fauna are critically-endangered on Earth currently.
- To set numbers more striking, one-fourth of all mammal species (the class of animals, humans belong to) is on the verge of extinction.
- International Union for the Conservation of Nature evaluates species in the wild and categorises the depletion on a Red List of Threatened Species.
Extinction has categories, and here’s how the world’s biologists define them.
- Critically endangered: Species staring at high probability of extinction. Sumatran rhinoceros and the Sumatran orangutan are critically endangered due to human actions like deforestation and agriculture.
- Extinct in the wild: Animals which are not seen living in their natural habitat anymore. Such species can only be seen in captivity. 27 California condors were taken into captivity to save them from extinct in 1987.
- Local extinction: Not a formal categorization, but locally extinct defines an animal which has disappeared from a known native location but lives in other areas. Grizzly bears live in the wild plenty but are locally extinct in California.
- Functional extinction: When the number of living members of a species is not even enough to efficiently support its ecosystem. 3.5 billion American chestnut trees were killed by a fungus leaving too few in North America.
- Global Extinction: Animals or species which are officially extinct across the globe and cannot be seen or found in any location, either in the wild or in captivity. This is determined after exhaustive searches in their habitat.
- Extinct species rediscovered: These are animals which have been observed alive after being declared for official extinction. Focused exploration in remote habitat like the IUCN’s Amphibian Specialist Group which rediscover a few species like the Hula painted frog in 2010.
- Discovered endangered: Again unofficial, but this is what you’ll call species that are discovered in small numbers in unfavourable habitats. Manduriacu glass frog found in mining areas of the Ecuadorian Andes is newly discovered but is struggling for survival.