Living organisms multiplied, thrived, and diversified over billions of years, occupying the Earth’s ecosystem. However, species extinctions have also been a part of the evolutionary life cycle. The balance can be tipped when the loss of species rapidly outpaces the formation of new ones, enough that it could elicit what is called the mass extinction events.
The sixth mass extinction
Biologist Paul Ehrlich co-authored research in 2015, which declared that the world’s sixth mass extinction is happening. It refers to the biological annihilation of species largely due to the exploitation of the planet by people. Now, Ehrlich and his colleagues from the UNAM Institute of Ecology and Missouri Botanical Garden's Plant Science Department have an update. They said that the extinction rate is accelerating and is even likely much bigger than they previously thought. This was after they analyzed thousands of vertebrate species.
The study only highlights that endangered species are not just limited to gorillas, tigers, and rhinos that we can think of. The scope of extinction is even much wider, the authors said.
According to Ehrlich and the team in the current study, more than 500 land-walking vertebrate species are on the brink of extinction and such extinction undermines nature’s ability to provide significant services to humans on Earth. Their study appeared in the journal Proceedings of the National Academy of Sciences (PNAS) of the United States of America.
Human impacts on wildlife
The authors likewise pointed out how human activities, particularly wildlife trade, wiped out hundreds of species and pushed more to the brink of extinction. Humans cause changes in the environment that hurt plant species and animals. We take up more space on the planet for our cities and homes, pollute habitats, kill animals, and illegally hunt them. Such human activities take habitats and resources away from animals and plants.
The list of land-walking vertebrates that are on the brink of extinction includes 74 mammals, 41 reptiles, 335 birds, and 65 amphibians. “The ongoing sixth mass extinction may be the most serious environmental threat to the persistence of civilization because it is irreversible,” the study reads.
The scientists estimate that in the entire 20th century, which began in January 1901 and ended in December 2000, at least 543 land-walking vertebrates went extinct. In the normal course of evolution, extinctions of such numbers would have taken 10,000 years. Examples include the Round Island burrowing boa, golden toad, and the ivory-billed woodpecker. In the next two decades, the same number of species will more likely go extinct as well and the cascading effects of extinction comprise the intensification of human health threats, including the Covid-19.
Ehrlich from the Department of Biology of Stanford University told research news site Science Daily that when humans begin to exterminate the species of other creatures and the population, it is destroying the working parts of its life-support system. He likened it to “sawing off the limb on which it is sitting.” In the public mind today, the origin of the Covid-19 story is that someone at the seafood market in Wuhan, China was infected with a virus from an animal. While it is not conclusive, scientists say that the coronavirus originated in bats or it spread to pangolins and humans.
Ehrlich emphasized that the conservation of endangered species should be elevated to a global and national emergency for institutions and governments in the same manner to climate disruption to which mass extinction is associated.
To better understand the extinction risk faced by some creatures nowadays, the team looked at the distribution and abundance of critically endangered species utilizing data form the Birdlife International and the International Union for the Conservation of Nature (IUCN) Red List. They found that 1.7% of 515 out of the 29,400 species analyzed are currently on the brink of extinction with only less than a thousand individuals remaining in every species.
Study lead author Gerardo Ceballos said that the actions that we take in the next two decades will define the fate of millions of species. Humans are now facing the final opportunity to make sure that the services nature offers us will not get irretrievably sabotaged, he added.
Species that are on the brink of extinction are found mainly in subtropical and tropical regions, areas that are heavily impacted by human activities. The study concluded that the loss of endangered creations will have a domino effect on other species as well.
World Wildlife Fund’s Living Planet Report 2018, which documents the state of the planet, shows that the wildlife populations have declined by 60% globally between 1970 and 2014. WWF’s executive director of science and conservation Mike Barrett, who is not involved in the Stanford study, said that we are now “sleepwalking” towards the edge of the cliff.
Main threats to wildlife populations
The main threats to wildlife populations around the world are exploitation (37%), habitat degradation or change (31.4%), habitat loss (13.4%), climate change (7.1%), invasive species or genes (5.1%), pollution (4%), and disease (2%), according to database company Statista. Meanwhile, the main driver for the decline of the number of vertebrates is habitat loss. Forest degradation and loss are mostly caused by the intensive harvesting of wood and timber for fuel and other forest products, the expansion of agricultural land, and also overgrazing.
Despite knowing that more than 20% of the world’s oxygen is produced in the Amazon Rainforest and that more species are found there than anywhere else in the world, the world’s largest rainforest is facing a multitude of threats. WWF estimates that 27% of the Amazon biome will be without trees by 2030 if the current deforestation rate continues.
The IUCN Red List of Threatened Species
The International Union for Conservation of Nature’s Red List of Threatened Species, which is the most comprehensive information source on the global extinction risk status of plant species, fungus, and animals, also published that 41% of amphibians, 25% mammals, 34% conifers, 33% reef corals, 30% sharks and rays, 14% birds, and 27% of selected crustaceans are now threatened with extinction. Some species whose populations are decreasing include the spoon-billed Sandpiper, Scimitar-horned Oryx, Echinodium renauldii, and Short-eared dog.
Science has always shown us the harsh reality that nature is enduring at our hands. Species by species, the shrinking wild place and wildlife numbers are signs of the tremendous pressure and impact humans are exerting on the Earth, undermining every living thing that sustains us.