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The Holocene Extinction

In the last 450 million years, our planet has faced five major extinction events, each destroying 70-95% of the species of plants, animals and microorganisms that existed previously. These events were caused by catastrophic natural disasters - massive volcanic eruptions, depletion of ocean oxygen, and collision with an asteroid, to name a few. In each event, it took millions of years to regain the numbers of species comparable to those before the extinction event. As such, an estimated 2% of the species that ever lived are alive today.

For humans that live maybe 80 or 90-some years, these extinction events and large timescales may be hard to wrap our minds around. However, for the first time in its history, our planet is now experiencing an ongoing extinction event thousands of times faster than the “normal” rates, and the cause isn't some enormous natural disaster - it's us. Referred to by many scientists as the Holocene Extinction, recent studies have helped to shed light on just how extreme the situation is and what ramifications we can expect as the human race has expanded its control over the planet and its resources.

Photo credit: National Geographic

The word “Holocene” is the name given to the current geological epoch we are in, which began around 11,700 years ago. It corresponds with the rapid proliferation, growth, and impact that humans as a species have had worldwide. Fast forward to today, and this impact cannot be understated. According to a recent analysis, more than 500 species of land animals are on the brink of extinction and are likely to be lost within 20 years; the same number were lost over the whole of the last century.The analysis, published in the journal Proceedings of the National Academy of Sciences, looked at data on 29,400 land vertebrate species compiled by the IUCN Red List of Threatened Species and BirdLife International. The scientists identified 515 species with populations below 1,000 and about half of these had fewer than 250 individuals remaining. The land vertebrates on the brink of extinction, with fewer than 1,000 individuals left, include the Sumatran rhino, the Española giant tortoise and the harlequin frog. Historic data for 77 of these species shows that they had lost 94% of their populations in the last century. Further, more than 400 vertebrate species became extinct in the last century, extinctions that would have taken up to 10,000 years in the normal course of evolution, illustrating humanity’s profound effect on the planet and those that live on it. The analysis also showed that 388 species of land vertebrates had populations under 5 000 individuals and 84% lived in the same regions as the species with populations under 1,000, creating the conditions for a domino effect. The scientists warned that ‘extinction breeds extinction’, where close ecological interactions of species on the brink tend to move other species towards extinction, creating the domino effect.

Pile of bison skulls (1870). Photo source: Wikimedia Commons.

When the number of individuals in a population or species drops too low, its contributions to ecosystem functions and services become unimportant, its genetic variability and resilience is reduced, and its contribution to human welfare may be lost. An example of this is the bison, which was a keystone species in North America. At one time, it was maintaining the entire ecosystem, supplying meat, robes)and fertilizers to Native Americans, and later to Europeans. Is it estimated that 200 years ago, there were 30 to 60 million individuals, but overharvesting for meat and skins and land conversion for farming decimated most populations. By 1884, there were 325 individuals left. They have since recovered to 30,000 wild bison and 500,000 living in enclosures, but the species has not reclaimed its ecological role and its habitats- the prairies- have been mostly destroyed.

A recent United Nations report has determined that since pre-industrial times, humans have altered 73 percent of the planet's land and 66 percent of its marine ecosystems. This alteration varies by location, from strip mining for valuable minerals to dumping trash into bodies of water. The bottom line is that we're shooting ourselves in the foot, polluting and destroying our once pristine environments. We're also threatening our own food supply - by overfishing the oceans and exhausting once fertile land, agriculture as a whole is at risk due to reduced biodiversity. 40% of insects are at risk of extinction, including bees which play a crucial role in pollination, and over 25% of large livestock breeds are at risk as well. We're destroying critical plant species at a breakneck pace - 600 species of plants have gone extinct in the last 250 years, a rate 500 times faster than would have occurred before human interference. Our population continues to grow as well - it's estimated there will be 8.6 billion people on earth by 2030 and 9.8 billion by 2050. More people means more demand for resources and land, and so we need to be more conscious of how we use available land and resources. We'll be in a pretty tough spot in the coming decades, so what do we do?

UN Summit on Biodiversity (2020). Photo source: Summit on Biological Diversity.

In early January 2020 the UN Summit on Biological Diversity released a plan to adapt and respond to the ongoing biodiversity crisis we've created. The new plan states that biodiversity and the benefits it provides are fundamental to human wellbeing and a healthy planet. The plan’s framework aims to galvanize urgent and transformative action by governments and all of society, including indigenous peoples and local communities, civil society, and businesses, to achieve the outcomes. The main goal is to stabilize the planet’s threatened biodiversity by 2030 and allow ecosystems to recover by 2050.

So what specifics does the plan offer? One of the main methods of achieving the 2030 goals is through conservation, specifically giving protected status to areas important for biodiversity. The UN is aiming for 30% of these land and sea areas to be fully protected by 2030, with at least 10% of them under “strict protection”. Another crucial step outlined in the plan is the reduction of pollution. The framework aims to reduce pollution from plastic waste, biocides, and excess nutrients by at least 50%. Other methods include clamping down on the illegal trade of plant and animal species, ensuring that trade is done legally and sustainably. This will go a long way towards both protecting at-risk species and limiting the introduction of non-native species into fragile ecosystems.

There is time to save species and slow the Holocene extinction, but the window of opportunity is almost closed. We must save what we can, or lose the opportunity to do so forever. The fate of humanity and most living species is at stake; it is therefore imperative that we act now.

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