The ability to run fast and far was not enough to save dinosaurs from firestorms. Douglas Henderson
The catastrophic bushfires raging across much of Australia have not only taken a huge human and economic toll, but also delivered heavy blows to biodiversity and ecosystem function.
Already, scientists are warning of catastrophic extinctions of animals and plants.
Humans have seldom if ever seen fires like these, but we do know that wildfires have driven mass extinctions and reshaped life on Earth at least once before – when the asteroid strike that led to the demise of the dinosaurs sparked deadly global firestorms.
Australian biodiversity
Australia is one of only 17 “megadiverse” countries. Much of our species richness is concentrated in areas torched by the current bushfires.
While some mammals and birds face elevated extinction risk, things will be even worse for small, less mobile invertebrates (which make up the bulk of animal biodiversity).
For example, the Gondwana Rainforests of New South Wales and Queensland have been badly affected by the fires. These World Heritage listed forests are home to a rich diversity of insects and a huge range of land snails, some restricted to tiny patches.
The bushfires have been rightly described as unprecedented, and extinctions can play out over an extended period. The full gravity of the impending catastrophe is not yet clear.
Fire has driven extinctions before
There have been greater burnings in the deep past, as we can see from the fossil record. They provide strong and disturbing evidence of how fire drove widespread extinctions that completely reshaped life on Earth.
Around 66 million years ago, a mass die-off called the Cretaceous–Paleogene extinction event famously put an end to the reign of dinosaurs (sparing only birds). This event erased 75% of the planet’s species.
Scientists agree these extinctions were primarily caused by an asteroid about 10 kilometres wide crashing into present-day Mexico, blasting a huge crater the size of Tasmania.
A nuclear winter followed the impact, as fine particles thrown up into the atmosphere blocked sunlight for years. The extended frozen darkness killed ecosystems from plants and phytoplankton upwards.
Recent research shows that global wildfires were likely also an important driver of extinctions, at least for life on land.
The asteroid blasted flaming debris across the atmosphere. Massive deposits of soot found in the fossil record at this precise time suggest most of the Earth’s forests went up in smoke, though these cataclysmic calculations remain controversial.
Only animals that could escape fire survived
The fossil record of land-dwelling animals – especially reptiles, birds and mammals – attests to the deadly efficiency of what has been dubbed the dinosaur firestorm. The nature of the victims and survivors is very relevant to current events.
The land animals that made it through the extinction all lived in ways that could confer resilience to heat and fire, such as living partly in water, being able to burrow or hide in deep crevices, or being able to escape rapidly by flight.
Land vertebrates that survived the ancient wildfires were either amphibious (crocodiles, freshwater tortoises), small enough to burrow or shelter (early rodent-sized mammals), or both amphibious and burrowing (platypuses). Michael Lee
Among reptiles, crocodilians and freshwater tortoises (both amphibious) sailed through. Worm-lizards and burrowing snakes survived, but surface-dwelling lizards and snakes were hard hit.
Among mammals, platypus-like monotremes (aquatic and burrowing) clung on, as did tiny rodent-like placental mammals (able to burrow, or hide in deep crevices), but all large placental mammals died. And while at least some birds survived, all their large, earth-bound, dinosaurian relatives perished.
In fact, it appears that every land-dwelling animal species larger than a domestic cat was ultimately doomed, unless it could swim, burrow or fly.
Even these abilities did not guarantee survival: they merely gave creatures a slightly better chance. For instance, pterosaurs could fly well, but still went extinct, along with most bird species.
Deforestation in ancient wildfires spared some ground-foraging birds but obliterated tree-dwelling, perching birds. Michael Lee
Recent research suggests perching birds –- which need forests to live in –- were essentially eliminated when most of the world’s trees disappeared. The sole avian survivors were ground-foragers similar to chickens and rails, and it took millions of years for new perching birds (modern songbirds) to re-evolve.
By exterminating many species, and doing so highly selectively, the global wildfires (alongside other effects of the asteroid impact) totally restructured Earth’s biosphere.
What about the current fires?
The recent rampant bushfires are regional rather than global (e.g. Australia, the Amazon, Canada, California, Siberia), and are burning less land cover than the worst-case dinosaur firestorm scenario.
Yet their long-term extinction effects could also be severe, because our planet has already lost half its forest cover due to humans. These fires are hitting shrunken biodiversity refuges that are simultaneously threatened by an anthropogenic cocktail of pollution, invasive feral species, and climate change.
The ancient catastrophe provides strong evidence, written in stone, that firestorms can contribute to extensive extinctions, even among large vertebrates with large distributions and high mobility.
It also shows certain types of organisms will bear the brunt of the impact. Entire guilds of similar species could vanish, severely impacting ecosystem function.
It took millions of years of regeneration and evolution for our planet’s biosphere to recover from the nuclear winter and wildfires of the asteroid impact. When a new world order eventually emerged, it was radically different: the age of dinosaurs gave way to the age of mammals and birds.
About the Author
Mike Lee, Professor in Evolutionary Biology (jointly appointed with South Australian Museum), Flinders University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Related Books
Life After Carbon: The Next Global Transformation of Cities
by Peter Plastrik , John Cleveland
The future of our cities is not what it used to be. The modern-city model that took hold globally in the twentieth century has outlived its usefulness. It cannot solve the problems it helped to create—especially global warming. Fortunately, a new model for urban development is emerging in cities to aggressively tackle the realities of climate change. It transforms the way cities design and use physical space, generate economic wealth, consume and dispose of resources, exploit and sustain the natural ecosystems, and prepare for the future. Available On Amazon
The Sixth Extinction: An Unnatural History
by Elizabeth Kolbert
Over the last half-billion years, there have been Five mass extinctions, when the diversity of life on earth suddenly and dramatically contracted. Scientists around the world are currently monitoring the sixth extinction, predicted to be the most devastating extinction event since the asteroid impact that wiped out the dinosaurs. This time around, the cataclysm is us. In prose that is at once frank, entertaining, and deeply informed, New Yorker writer Elizabeth Kolbert tells us why and how human beings have altered life on the planet in a way no species has before. Interweaving research in half a dozen disciplines, descriptions of the fascinating species that have already been lost, and the history of extinction as a concept, Kolbert provides a moving and comprehensive account of the disappearances occurring before our very eyes. She shows that the sixth extinction is likely to be mankind's most lasting legacy, compelling us to rethink the fundamental question of what it means to be human. Available On Amazon
Climate Wars: The Fight for Survival as the World Overheats
by Gwynne Dyer
Waves of climate refugees. Dozens of failed states. All-out war. From one of the world’s great geopolitical analysts comes a terrifying glimpse of the strategic realities of the near future, when climate change drives the world’s powers towards the cut-throat politics of survival. Prescient and unflinching, Climate Wars will be one of the most important books of the coming years. Read it and find out what we’re heading for. Available On Amazon
From The Publisher:
Purchases on Amazon go to defray the cost of bringing you InnerSelf.comelf.com, MightyNatural.com, and ClimateImpactNews.com at no cost and without advertisers that track your browsing habits. Even if you click on a link but don't buy these selected products, anything else you buy in that same visit on Amazon pays us a small commission. There is no additional cost to you, so please contribute to the effort. You can also use this link to use to Amazon at any time so you can help support our efforts.
