Evidence suggests the world is going through its sixth mass extinction, as species are disappearing at an abnormally high rate. Most species could become extinct by 2200 if the current rate of extinction continues. The implications for human health and well-being are dire, but not inevitable.
Nearly 99% of all species that have ever existed have disappeared since the first hints of life existed on Earth more than 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 over time; rather, they tend to unfold in large bursts interspersed with periods of relative stability. Scientists refer to these extinction pulses as mass extinction events.
About 540 million years ago there was a speciation explosion called the Cambrian Explosion. Since then, the fossil record has identified at least five mass extinction events and likely dozens of smaller ones.
One of the most infamous of these events happened around 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 massive, at least 75% of all species on Earth must disappear within a “short” time frame, i.e. less than 2.8 million years.
Throughout history, humans have caused smaller extinction events dating back to the late Pleistocene (about 50,000 years ago) to the early Holocene (about 12,000 years ago); when “megafauna” like woolly mammoths, giant sloths, diprotodons and cave bears disappeared from almost every continent within a few thousand years.
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From around the 14th century, the expansion of European colonialism across the world led to a cascade of extinctions, first on the islands, before spreading to parts of the mainland as the will to he exploitation of natural resources intensified.
More than 700 species of vertebrates and 600 species of plants have disappeared over the past 500 years.
Some say these extinctions are unlikely to qualify as mass extinctions in the modern era because they do not meet the 75% threshold.
However, these are only the extinctions that humans have recorded. Most species go extinct before they are even discovered, with up to 25% 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, floods and fires more frequent and more intense and a deterioration of human health.
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We are responsible for the emergence of diseases like HIV/AIDS, Ebola and COVID-19 because of our collective disregard for the integrity of natural ecosystems.
However, with a little effort and longer-term planning, we could make our future a little less scary. We could potentially limit the damage if societies around the world adopted some fundamental, but achievable, changes.
(With agency contributions)