Evidence suggests that the world is going through its sixth mass extinction, as species are vanishing at an abnormally high rate. Most species could be extinct by 2200 if the current rate of extinction continues. The implications for human health and wellbeing are dire, but not unavoidable.
Nearly 99 per cent of all species that have ever existed have gone extinct since the earliest inklings of life existed on Earth, over 3.5 billion years ago.
The evolution of species takes place over time, and as species evolve, they replace other extinct species.
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Extinctions and speciations, however, do not occur uniformly through time; Rather, they tend to take place in large pulses interspersed with periods of relative stability. Scientists refer to these extinction pulses as mass extinction events.
Around 540 million years ago, there was a burst of speciation called the Cambrian explosion. Since then, the fossil record has identified at least five mass extinction events and probably scores of smaller ones.
One of the most infamous of these events occurred about 66 million years ago when a giant asteroid crashed into Earth in what is now the Gulf of Mexico.
For an extinction to be considered mass, at least 75 per cent of all species on Earth have to become extinct within a ‘short’ time frame, ie less than 2.8 million years.
Throughout history, humans have caused smaller extinction events dating back to the late Pleistocene (around 50,000 years ago) to the early Holocene (around 12,000 years ago); when ‘megafauna’ such as woolly mammoths, giant sloths, diprotodons, and cave bears disappeared from nearly every continent over a few thousand years.
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From about the 14th Century onward, the expansion of European colonialism throughout the world led to an extinction cascade, first on islands, before spreading to areas of the continental mainland as the drive to exploit natural resources intensified.
More than 700 vertebrate species and 600 plant species have gone extinct in the last 500 years.
Some say that there is no likelihood that these extinctions would qualify as mass extinctions in the modern era, since they do not meet the 75 per cent threshold.
However, those are just the extinctions humans have recorded. Most species go extinct before they are even discovered, with up to 25 per cent of extinctions going unnoticed by humans.
We lose the services provided by species when they disappear. The result is reduced carbon sequestration, exacerbated climate change, reduced pollination and increased soil degradation, decreased food production, poorer air and water quality, more frequent and intense flooding and fires, and a deterioration of human health.
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We are to blame for the emergence of diseases like HIV/AIDS, Ebola, and COVID-19 due to our collective disregard for the integrity of natural ecosystems.
However, with a little effort and longer-term planning, we could make our future just that little bit less ghastly. We could potentially limit the damage if societies around the globe embraced certain fundamental, yet achievable, changes.
(With inputs from agencies)