Though it may sound surprising, land plants may have been accessories to the crime. During the Devonian, plants hit on several winning adaptations, including the stem-strengthening compound lignin and a full-fledged vascular structure. These traits allowed plants to get bigger—and for their roots to get deeper—than ever before, which would have increased the rate of rock weathering.
The faster rocks weathered, the more excess nutrients flowed from land into the oceans. The influx would have triggered algae growth, and when these algae died, their decay removed oxygen from the oceans to form what are known as dead zones. In addition, the spread of trees would have sucked CO 2 out of the atmosphere, potentially ushering in global cooling. To add to the puzzle, not only did some creatures go extinct during the late Devonian, but species diversification slowed down during this time.
The slowdown may have been caused by the global spread of invasive species , as high sea levels let creatures from previously isolated marine habitats mix and mingle, which let ecosystems around the world homogenize. The cataclysm was the single worst event life on Earth has ever experienced. Over about 60, years, 96 percent of all marine species and about three of every four species on land died out. Of the five mass extinctions, the Permian-Triassic is the only one that wiped out large numbers of insect species.
Marine ecosystems took four to eight million years to recover. Find out more about the devastation of the Permian-Triassic mass extinction. A sail-backed edaphosaurus forages amid a Permian landscape in this artist's depiction. These primitive predators, along with their close relatives the dimetrodons, though dinosaur-like in appearance, are actually considered the forerunners of mammals.
Scientists think their large back fins were used to regulate body temperature. The eruption triggered the release of at least Adding insult to injury, magma from the Siberian Traps infiltrated coal basins on its way toward the surface, probably releasing even more greenhouse gases such as methane. The resulting global warming was downright hellish.
In the million years after the event, seawater and soil temperatures rose between 25 to 34 degrees Fahrenheit.
By At the time, almost no fish lived near the Equator. As temperatures rose, rocks on land weathered more rapidly, hastened by acid rain that formed from volcanic sulfur.
Just as in the late Devonian, increased weathering would have brought on anoxia that suffocated the oceans. Climate models suggest that at the time, the oceans lost an estimated 76 percent of their oxygen inventory. Life took a long time to recover from the Great Dying, but once it did, it diversified rapidly. Different reef-building creatures began to take hold, and lush vegetation covered the land, setting the stage for a group of reptiles called the archosaurs: the forerunners of birds, crocodilians, pterosaurs, and the nonavian dinosaurs.
But about million years ago, life endured another major blow: the sudden loss of up to 80 percent of all land and marine species. An artist's rendering shows hatchling nothosaurs heading for the safety of water as a hungry but terrestrial Ticinosuchus attacks near a lagoon in ancient Switzerland.
Nothosaurs lived during the mid- and late Triassic period and were among the earliest reptiles to take to the sea. Because nothosaurs may have had to come ashore to lay eggs, the eggs and hatchlings would have been vulnerable to Ticinosuchus.
Yet once the hatchlings reached deeper waters, they were safe—for the moment. At the end of the Triassic, Earth warmed an average of between 5 and 11 degrees Fahrenheit, driven by a quadrupling of atmospheric CO 2 levels. This was probably triggered by huge amounts of greenhouse gases from the Central Atlantic Magmatic Province, a large igneous province in central Pangaea, the supercontinent at the time.
Remnants of those ancient lava flows are now split across eastern South America, eastern North America, and West Africa. The Central Atlantic Magmatic Province was enormous. Its lava volume could cover the continental U. The uptick in CO 2 acidified the Triassic oceans, making it more difficult for marine creatures to build their shells from calcium carbonate. The third and most devastating of the Big Five occurred at the end of the Permian period around million years ago.
Some of the suggested causes include an asteroid impact that filled the air with pulverised particle, creating unfavourable climate conditions for many species.
These could have blocked the sun and generated intense acid rains. The demise of the dinosaur super predators gave mammals a new opportunity to diversify and occupy new habitats, from which human beings eventually evolved. The Earth is currently experiencing an extinction crisis largely due to the exploitation of the planet by people.
The most accepted background rate estimated from the fossil record gives an average lifespan of about one million years for a species, or one species extinction per million species-years. But this estimated rate is highly uncertain, ranging between 0. Whether we are now indeed in a sixth mass extinction depends to some extent on the true value of this rate. Even considering a conservative background rate of two extinctions per million species-years , the number of species that have gone extinct in the last century would have otherwise taken between and 10, years to disappear if they were merely succumbing to the expected extinctions that happen at random.
This alone supports the notion that the Earth is at least experiencing many more extinctions than expected from the background rate. Among land vertebrates species with an internal skeleton , species have been recorded going extinct since the year , or about 1.
This released a large amount of carbon dioxide into the atmosphere, causing a greenhouse effect that heated up the planet. As a result, weather patterns shifted, sea levels rose and acid rain beat down on the land. In the ocean, the increased levels of carbon dioxide dissolved into the water, poisoning marine life and depriving them of oxygen-rich water, according to the Sam Noble Museum in Oklahoma.
At the time, the world consisted of one supercontinent called Pangaea , which some scientists believe contributed to a lack of movement in the world's oceans, creating a global pool of stagnant water that only perpetuated carbon dioxide accumulation. Rising sea temperatures also reduced oxygen levels in the water, Live Science previously reported. Corals were a group of marine life forms that were among the worst affected — it took 14 million years for the ocean reefs to rebuild to their former glory.
The Triassic period erupted in new and diverse life, and dinosaurs began to populate the world. Unfortunately, numerous volcanoes also erupted at that time.
Although it remains unclear exactly why this fourth mass extinction occurred, scientists think that massive volcanic activity occurred in an area of the world now covered by the Atlantic Ocean, according to MIT News. Similar to the Permian extinction, volcanoes released enormous amounts of carbon dioxide, driving climate change and devastating life on Earth.
Global temperatures increased, ice melted, and sea levels rose and acidified. As a result, many marine and land species became extinct; these included large prehistoric crocodiles and some flying pterosaurs.
There are alternative theories explaining this mass extinction, which suggest that rising carbon dioxide levels released trapped methane from permafrost, which would have resulted in a similar series of events, according to Discover magazine. The most famous of all the mass extinction events is the Cretaceous -Paleogene extinction — better known as the day the dinosaurs died. The "K" is from the German word "Kreide," which means "Cretaceous.
This punched a hole miles km wide and 12 miles 19 km deep, called the Chicxulub crater. The impact would have scorched all the land around it within miles 1, km and ended the million-year reign of the dinosaurs on Earth. What followed the impact were months of blackened skies caused by debris and dust being hurled into the atmosphere, Live Science previously reported.
This prevented plants from absorbing sunlight, and they died out en masse and broke down the dinosaurs' food chains. It also caused global temperatures to plummet, plunging the world into an extended cold winter. Scientists estimate that most extinctions on Earth at the time would have occurred in just months after the impact.
However, many species that could fly, burrow or dive to the depths of the oceans survived. For example, the only true descendants of the dinosaurs living today are modern-day birds — more than 10, species are thought to have descended from impact survivors. Humans might be the driving force behind this accelerated extinction event, but we are also the answer to stopping it. The world is awash with scientists, conservationists and environmentalists working in the laboratory, in conservation areas and in political battlegrounds to protect endangered species.
From tackling global pollution emissions in the Paris Agreement to the U. In particular, one of the biggest direct threats to endangered life is the illegal animal trade. In the wake of the current pandemic, wildlife markets have been thrust into the spotlight as not only being environmentally irresponsible, but potentially dangerous to human health through zoonotic diseases — those that jump from animals to humans — such as COVID These markets, trading live exotic animals or products derived from them, are found throughout the world.
For example, bear farms in Asia cage 20, Asiatic black bears for their bile, resulting in the decline of the wild population, according to Animals Asia. Lawmakers are tackling these kinds of markets with growing success.
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