The Sixth Mass Extinction Is Happening Now, And It Doesn’t Look Good To Us

By Corey Bradshaw, Flinders University Adelaide, Mar 2 (360info) Species are disappearing at an unusually high rate. Our efforts now will prevent a future too dreadful to contemplate.

Mounting evidence points to the world having entered a sixth mass extinction. If the current rate of extinction continues, we could lose most species by 2200. The implications for human health and well-being are dire, but not inevitable.

In the timeline of fossil evidence dating back to the first sight of any life on Earth – more than 3.5 billion years ago – nearly 99% of all species that have ever existed are now extinct. This means that as species evolve over time – a process known as “speciation” – they replace other species that are going extinct.

Extinctions and speciations do not occur at uniform rates over time; instead, they tend to occur in large pulses interspersed with long periods of relative stability. These extinction pulses are what scientists call mass extinction events. The Cambrian Explosion was a speciation explosion about 540 million years ago. Since then, at least five mass extinction events have been identified in the fossil record (and likely dozens of smaller ones).

Arguably the most infamous of these was when a giant asteroid crashed into Earth around 66 million years ago in what is now the Gulf of Mexico. The collision vaporized species immediately in the blast area.

Later, species were killed by climate change resulting from pulverized particles suspended in the atmosphere, as well as intense volcanic activity stimulated by the buckling of the earth’s crust following the impact of the asteroid. . Together, about 76% of all species present at the time became extinct, of which the dinosaurs’ demise is the best known. But the dinosaurs didn’t completely disappear – the survivors just evolved into birds.

To be classified as a mass extinction, at least 75% of all species on Earth must go extinct within a “short” geologic period of less than 2.8 million years. This delay seems long to us because modern man has only existed for about 200,000 years so far.

As a species, humans have been involved in smaller extinction events dating back to the late Pleistocene (about 50,000 years ago) to the early Holocene (about 12,000 years ago) when most “megafauna”, such as woolly mammoths, giant sloths, diprotodons and cave bears have disappeared from almost every continent in a few thousand years. Much later, the expansion of European settlers around the world from around the 14th century precipitated a cascade of extinctions first on the islands and then in areas of the continental mainland as the drive to exploit the natural resources was accelerating. Over the past 500 years, there have been over 700 documented extinctions of vertebrates and 600 plant species.

These extinctions are far from the 75% threshold to include the modern era among previous mass extinction events.

But these are only the extinctions that humans have recorded. In fact, many species go extinct before they are even discovered – perhaps up to 25% of total extinctions are never noticed by humans. Even accounting for undetected extinctions, the modern era still cannot be classified as a mass extinction event.

But it’s not the total number of extinctions that we should focus on; rather, it is the rate of extinction. If past mass extinctions took nearly three million years to ensue, we should instead be looking at how many species are going extinct per unit time versus the “background” rate of extinction that occurs between events. mass extinction.

According to the fossil record, the average “lifespan” of a species is around one million years, which equates to a background rate of around 0.1 to 2.0 extinctions per million “lifespans”. species-years”. This makes the number of extinctions seen in the modern era 10–10,000 times higher than the background rate. Even the most conservative estimates that ignore undetected extinctions firmly place the modern era well within the expected range to qualify as a mass extinction.

An optimist might argue that the loss rate will surely decrease over time, so it is unlikely that we will reach the 75% threshold. However, the outlook is not at all rosy. The devastation wrought to date means the rate of extinction will only accelerate. Most of the damage to Earth’s life support system has occurred over the past century. The global human population has tripled since 1950, and there are now approximately one million species at imminent risk of extinction due to massive population declines, representing approximately 10-15% of all complex life on Earth. Since the beginning of agriculture around 11,000 years ago, the total amount of vegetation on Earth has halved. Less than 15 percent of all wetlands recorded 300 years ago are still present today, and more than two-thirds of the world’s oceans are compromised to some degree by human activity. Not to mention climate change. Recent evidence suggests that global warming is causing up to ten times more extinctions than would be expected when looking only at a species’ upper temperature limit. In fact, when we take into account the relationships between species – such as predators based on their prey, parasites based on their hosts, or flowering plants based on their pollinators – future extinctions are set to explode.

The IUCN Red List tracks the most endangered species. But it also shows how little we know about species extinction.

A truly indifferent person might also argue that as long as the species that provide resources to modern societies survive, there is no reason to regard extinction as a problem. Evidence suggests otherwise. The loss of species also erodes the services that biodiversity provides to us. These include reduced carbon sequestration which exacerbates climate change, reduced pollination and increased soil degradation which compromises our food production, poorer water and air quality, more floods and fires. frequent and more intense and poorer human health. Even human diseases like HIV/AIDS, Ebola and COVID-19 are the result of our collective indifference to the integrity of natural ecosystems.

You could be forgiven for thinking that in the presence of overwhelming scientific evidence supporting the need to change our course, human societies and their leaders would prioritize damage control. In fact, the opposite is happening. Short-term interests, an economic system that concentrates wealth among a few individuals, the rise of right-wing populism with anti-environmental agendas and funded disinformation campaigns designed to protect short-term profits, mean there is little likely that we can make changes on a sufficient scale to avoid an environmental catastrophe. A dire future seems almost assured.

However, the bleak outlook does not justify inaction. On the contrary, we could potentially limit the damage if societies around the world adopted some fundamental, but achievable, changes. We could abolish the goal of perpetual economic growth and force companies to restore the environment using established mechanisms such as carbon pricing. We could limit undue corporate influence on political decision-making and end corporate lobbying of politicians. Educating and empowering women, including giving them greater self-determination in family planning, would help stem environmental destruction.

With a little effort and longer term planning, we could make our future a little less scary. (360info.org) AMS AMS

(This story has not been edited by the Devdiscourse team and is auto-generated from a syndicated feed.)


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