Past Mass Extinctions Linked to Changes in Global Climate
Planet Earth might be teetering on the brink of a sixth mass extinction event, climate change resulting in the huge loss of species associated with the Cretaceous mass extinction or the more devastating (in terms of species affected), Permian Great Dying. That is the conclusion reached in a documentary being aired on the Smithsonian channel in the United States tomorrow. The documentary entitled “Mass Extinction: Life at the Brink” explains what scientists now know about the Permian and Cretaceous extinction events, two of the five great extinctions recorded in the fossil record (Phanerozoic extinctions). The documentary also explores how our activities are altering the climate, which could lead to similar collapses within ecosystems.
Although global warming is still dismissed by some, most of the scientific community supports the theory that the Earth’s climate is changing and that the planet is getting warmer. One of the key points in the film concerns the issue of if the Earth warms very suddenly, when climate change is examined against the backdrop of geological time, then what would be the consequences?
This documentary and a book written by University of California (Berkeley) palaeontologist and professor of integrative biology, Anthony Barnosky (Dodging Extinction) is just one of a series of increasingly alarming accounts of the impact of climate change on our planet, produced by the academic community. Back in 2010, a United Nations report stated that about 30% of all the flora and fauna on Earth was in danger of dying out by the end of the 21st Century due to the rapid industrialisation of parts of the world and the West’s inability to curb greenhouse gases that were potentially leading to dramatic changes in climate.
To read more about the United Nations report: Are we Heading for a Sixth Mass Extinction Event?
Professor Barnosky and his wife, Dr Elizabeth Hadley (a biologist/ecologist at Stanford University), appear in the documentary, helping to explain the evidence that has been amassed that suggests climate change is happening and such shifts in Earth’s climate led to mass extinctions in the past.
Professor Barnosky, now in his early sixties explains:
” I go back to places where I was doing coal exploration geology, beautiful places in western Colorado and now the trees are all dead, mostly from beetle kill because winters have warmed enough so that the beetles can reproduce twice in a season rather than once. In my lifetime, I have seen it go from verdant forests to literally tens of thousands of acres of dead trees, and that’s just in Colorado. There are literally millions of square miles of dead trees up and down the Rocky Mountain chain. All because of greenhouse gases warming the atmosphere”.
A Table Listing the Five Major Extinction Events of the Phanerozoic
Table credit: Everything Dinosaur
The table above documents the five mass extinction events from the Phanerozoic Eon (the eon of visible life from approximately 545 million years ago to the present day). The table also provides information about the major animal groups affected.
The documentary film’s executive producer is evolutionary biologist Sean B. Carroll, he states that scientists and academics have learned more about what caused the great extinction events of the past. Dramatic events like asteroid impacts and massive volcanic eruptions led to climate change on a global scale wrecking the world’s ecosystems and devastating life on our planet.
Professor Carroll explained:
“We now know with high confidence from recent work that The Great Dying [Permian extinction event] was caused by massive volcanic eruptions underneath present-day Siberia and that just pumped out massive amounts of climate-changing gases, including massive amounts of carbon dioxide.”
Also appearing in the documentary programme is Walter Alvarez (University of California, Berkeley), who along with his late father, the physicist Luis Alvarez, first uncovered evidence that an extraterrestrial impact had struck the Earth at around the time of the demise of the dinosaurs. Whilst there has always been extinctions (known as the background rate of extinction), the programme makers warn that as humans reduce the habitat available for other species and alter the composition of the atmosphere, animals and plants are being pushed towards extinction twelve times higher than the background level.
For instance, temperatures may rise by perhaps as high as four degrees Celsius by the end of the 21st Century, a rise almost as great as during the end Permian extinction event, which resulted in the loss of some 95% of all life on Earth. It has been suggested that most of the coral reefs may vanish by the year 2070, as the oceans become more acidic due to increased levels of carbon dioxide in the atmosphere. This could result in the loss of 25% of the fish species in the sea that depend on coral reefs resulting in the loss of 10% of the ocean’s fisheries with direct implications for the human population.
There may be still time to help avert this catastrophe, recent agreements on the restricted use of fossil fuels and greenhouse gas emission limits if implemented effectively, could help minimise the impact. In the book, authored by Professor Barnosky, he proposes a series of steps that people can take to help prevent further global warming:
- Reduce the amount of intensively reared meat that you consume
- Avoid foods which contain palm oil (palm oil plantations replacing large amounts of natural forest)
- Only eat fish that has been sustainably harvested
In addition, the authors and the documentary makers urge people to lobby political and business leaders to help bring about fundamental changes in the way that we as a species perceive the natural world and its resources.