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The Sixth Mass Extinction | Earth Wise

February 16, 2022 By EarthWise Leave a Comment

Extinction is a natural part of life. Plants and animals disappear all the time. When one species goes extinct, its place in the ecosystem is typically filled by another. The so-called normal rate of extinction is thought to be somewhere between 0.1 and 1 species per 10,000 species per 100 years.

A mass extinction event is when species disappear at a much faster clip than they can be replaced. By definition, mass extinction is when about three-quarters of the world’s species are lost in a short amount of time on a geologic scale, which is measured in millions of years.

There have been five previous mass extinction events throughout the history of life on earth. Today, many experts warn that a sixth mass extinction event is already underway – the first since dinosaurs were wiped out some 65 million years ago. While previous mass extinctions were the result of extreme natural phenomena like volcanic eruptions and asteroid strikes, this one is a result of human activities.

Researchers from the University of Hawai’i at Manoa and the National Museum of Natural History in France recently published a comprehensive assessment of evidence of this ongoing extinction event. The researchers estimated that since the year 1500, Earth could already have lost between 7.5% and 13% of the two million known species on Earth. This amounts to a staggering 150,000 to 260,000 species.

While mitigating the effects of climate change and reducing the rates of habitat loss would help, raising awareness of this crisis and its fallout for all life forms – including us – would be most effective in driving change.

The time we have to avoid dramatic consequences is rapidly running out.

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Strong evidence shows Sixth Mass Extinction of global biodiversity in progress

Photo, posted September 18, 2015, courtesy of Tony Webster via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Why Have Crocodiles Changed So Little Over Time? | Earth Wise

February 9, 2021 By EarthWise Leave a Comment

Crocodiles today look very similar to ones from the Jurassic period some 200 million years ago. In fact, there are very few species of crocodilians alive today – approximately two dozen to be exact. Many other species have achieved a diversity of many thousands of species in the same amount of time.

During prehistoric times, many more types of crocodiles roamed the earth, including some as big as dinosaurs and other serpentine forms that lived in the sea.

According to findings by scientists at the University of Bristol in the U.K., a stop-start pattern of evolution could explain why crocodiles have changed so little over time. In the study, which was recently published in the journal Nature Communications Biology, researchers describe how crocodiles follow a pattern of evolution known as “punctuated equilibrium.” In other words, crocodiles’ rate of evolution is generally slow, but occasionally picks up because the environment has changed.

According to the research team, this slow rate of evolution is how crocodile diversity became so limited. It appears crocodiles arrived at a body that was efficient and versatile. They didn’t need to continue to change in order to survive.

This efficiency and versatility could be an explanation for why crocodiles survived the meteor impact that wiped out the dinosaurs. Since crocodiles can’t control their body temperature and rely on the environment for warmth, they generally fare better in warm conditions. During the age of dinosaurs, the climate was warmer than it is today, which could explain why crocodile diversity was higher.

The scientists next step is to try to figure out why some prehistoric crocodiles died out while others did not.

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Why crocodiles have changed so little since the age of the dinosaurs

Photo, posted December 26, 2012, courtesy of Nicholas Smith via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Ocean Acidification And Mass Extinction

November 26, 2019 By EarthWise Leave a Comment

Since the industrial revolution, the concentration of carbon dioxide in the atmosphere has increased due to the burning of fossil fuels and land use changes. The ocean absorbs about 30% of the CO2 that is released in the atmosphere. As the levels of atmospheric CO2 increase, so do the levels in the ocean.

When CO2 is absorbed by the ocean, a series of chemical reactions occur, resulting in seawater becoming more acidic. Ocean acidification threatens calcifying organisms, such as clams and corals, as well as other marine animals, like fish. When these organisms are at risk, the entire marine ecosystem may also be at risk.

In fact, according to research recently published in the journal Proceedings of the National Academy of Sciences, fossil evidence from 66 million years ago has revealed that ocean acidification can cause the mass extinction of marine life. Researchers analyzed seashells in sediment laid down shortly after a giant meteorite hit earth. This strike wiped out the dinosaurs and 75% of marine species. Chemical analysis of the shells revealed a sharp drop in the PH of the ocean over hundreds of years after the meteorite strike. The meteorite impact vaporized rocks, causing carbonic acid and sulphuric acid to rain down, acidifying the ocean. The strike also resulted in mass die-off of plants on land, increasing atmospheric CO2.

Researchers found that the pH dropped by 0.25 pH units in the 100 to 1,000 years after the meteorite strike. Alarmingly, scientists expect the pH of the ocean to drop by 0.4 pH units by 2100 if our carbon emissions continue as projected.

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Ocean acidification can cause mass extinctions, fossils reveal

Photo, posted March 16, 2017, courtesy of Zachary Martin via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Earth Day

April 22, 2019 By EarthWise Leave a Comment

Today is Earth Day. On April 22, 1970, millions of Americas took to the streets in peaceful demonstrations in favor of environmental reform. Since that first time, Earth Day has now become a global event each year. Estimates are that as many as a billion people in 192 countries take part in Earth Day events.

This year, the theme for Earth Day is “Protect our Species.” The focus is on the fact that the world is facing the greatest rate of extinction since the demise of the dinosaurs more than 60 million years ago.

But unlike the extinctions from that time that were linked to so-called acts of god like asteroid collisions, the rapid extinction of species in our world today is mostly the result of human activity.

The global destruction and rapid reduction of plant and wildlife populations are directly linked to climate change, deforestation, habitat loss, trafficking and poaching, unsustainable agriculture, pollution, and pesticides.

In order to stem the tide of destruction, the Earth Day Network is asking people to help raise awareness about the accelerating rate of extinction of millions of species and the causes and consequences of this phenomenon. We need to push for the creation of policies that protect broad groups of species as well as individual species and their habitats. There needs to be a global movement that embraces nature and its values. And we need to eat less meat and curtail the use of pesticides and herbicides.

We share the planet with many species, and we need them to be here in order to sustain our own species. Something to remember on Earth Day 2019.

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Earth Day Network

Photo, posted January 24, 2012, courtesy of Jonas Bengtsson via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Mammals Can’t Seem To Evolve Fast Enough

November 1, 2018 By EarthWise Leave a Comment

Our planet has been through five upheavals over the past 450 million years. During each one, the environment on earth changed so dramatically that most plant and animal species became extinct. After each of these mass extinction events, evolution slowly filled the gaps in the environment with new species.

Is The World’s Largest Sea Turtle No Longer Endangered?

January 29, 2018 By EarthWise 3 Comments

The rapid disappearance of many plants and animals around the world has many scientists saying we are experiencing a sixth mass extinction – the first since the dinosaurs were wiped out some 66 million years ago. Despite all sorts of conservation efforts, living things are struggling as a result of climate change, habitat loss, and countless other natural and manmade pressures. Conservation success stories have been few and far between.

Vulnerable to Extinction

January 10, 2017 By EarthWise

According to the International Union for the Conservation of Nature, the world’s tallest land mammal may be in trouble. Giraffe populations have declined dramatically over the past 30 years, falling to approximately 97,000 from 163,000 in the 1980s.

The First Mass Extinction Since Dinosaurs

August 11, 2015 By EarthWise

Earth’s current biodiversity is the highest in the history of life – ever. It’s the product of three and a half billion years of evolution. But a new study warns that a tipping point is on the horizon.