Mass extinction or biotic crisis is a widespread and rapid decrease of global biodiversity within a relatively short period of geological time. Such an event is identified by a sharp decrease in the diversity and abundance of multicellular organisms. Earth has witnessed five mass extinctions in the past, when more than 75% of species disappeared.

The first was in the Late Ordovician. This ancient crisis which occurred around 445 million years ago saw two major waves of extinction, both caused by climate change associated with the advance and retreat of ice sheets in the southern hemisphere. This makes it the only major extinction to be linked to global cooling. This extinction caused the demise of around 86% of Ordovician life which were sea creatures.

The second was in the Late Devonian. This period is now regarded as a number of “pulses” of extinction spread over 20 million years, beginning 375 million years ago. It saw again the extinction of around 75% of marine genera; among the species killed off were many corals, trilobites, sponges and the heavily armored fish known as placoderms. This extinction has been linked to a major volcanic eruption that might have caused rapid fluctuations in sea levels and reduced oxygen levels in the oceans.

The third was in the Middle Permian. This period which occurred 251 million years ago recorded 96% species lost. It was termed “the great dying”. Among the species wiped out, were brachiopods and single-celled benthic foraminifera.

The fourth was in the End of Triassic. This occurred 200 million years ago recording about 80% species lost. This included more trilobites, corals, and whole branches of species of terrestrial animals. The extinction was triggered by a vast eruption of the Siberian Traps, a gigantic and prolonged volcanic event that covered much of modern day Siberia.

The fifth was in the Late Cretaceous. This period occurred 66 million years ago recording 76% of all species lost. It was caused by another large-scale eruption, this time of the Central Atlantic Magmatic Province, which heralded the splitting of the supercontinent Pangaea and the initial opening of what later became the Atlantic Ocean. This extinction led to the final demise of the eel-like conodonts, as well as the largest known extinction of scleractinian corals. It also wiped out a significant proportion of terrestrial reptiles and amphibians.

*Long-tailed pangolin - currently one of the most threaten species (all pangolin species)

The five mass extinctions were caused by catastrophic natural events but today Humans are bringing about The Sixth Mass Extinction of life on Earth. Scientist suspect we’re living through the sixth mass extinction. Earth's population of wild vertebrates (all mammals, birds, reptiles, amphibians and fish) declined 58% from 1970 to 2012. Scientist says if extinction rate does not decrease soon, global wildlife populations could drop by 67 % as early as 2020. The primary causes of this extraordinary worldwide wildlife population decline are attributed to human activities such as poaching, habitat degradation, climate change, invasive species, and diseases.

*bushfires - one of the biggest threat to the environment causing huge habitat losses

In a world full of hope we believe current trends can be reverse if collective action is taken by all humans big or small, young or old around the world. In our little efforts join CASUD to prevent the sixth mass extinction in the Abonfen forest in the Bamenda Highlands of Cameroon through the planting of trees to revive degraded wildlife habitats. This action will help maintain a delicate balance among living things and thus sustain a healthy ecosystem.

Manka Grace

@manka (read more about me here)
content creator of @kedjom-keku association and fund-raising and upvoting bot @treeplanter
member of Forest Friendly Family

Our Steemit team:

@martin.mikes - coordinator/co-founder of @kedjom-keku, @treeplanter and Forest Friendly Family
@the greens - partner
@raserrano - IT specialist (admin of @treeplanter)

---

sources:

1. https://cosmosmagazine.com/palaeontology/big-five-extinctions
2. https://theconversation.com/five-mass-extinctions-and-what-we-can-learn-from-them-about-the-planet-today-79971