Although it's sad to think about, extinction has always been a natural part of life on our planet. Over millions of years, countless species, both big and small, have completely disappeared, leaving behind little more than fossils as evidence they once roamed the wilds. However, while extinction is a natural process, the rate at which species are going extinct today is far from it, with human activity playing a substantial role in accelerating this decline. In this article, we'll help you understand how extinction works, take a journey back into the great mass extinctions of the past, and talk about several major reasons species are still dying out today.
What is Extinction?
Simply put, an entire species becomes extinct when the last individual dies. One this occurs, it's essentially gone for good (although there are dubious claims species can be brought back through cloning) and it's genes and role in the ecosystem as a whole disappears with it.
It's estimated that more than 99% of all the species that have ever called Earth home are now extinct.
Most extinctions rarely happen in a flashy manner either. In fact, many populations of species have been lost without humans noticing until it's too late. Mainly due to the rapid changing of their environment while new species evolve to take their place (officially called background extinction).
Extinct in the Wild
That being said, it's not all that uncommon in the modern day for species that no longer exist in the wild to still have captive populations in places like zoos or botanical gardens.. Here's a couple of examples:
- Père David's Deer: Once native to China, this deer was once only found in captive collections. However, conservation efforts have seen it slowly reintroduced to protected areas. Despite this, it's IUCN classification still remains Extinct in the Wild as its unclear whether this effort will prove successful in the long run
- Socorro Dove: Originally found in Mexico, this dove was las spotted in the wild way back in 1972. Fortunately, captive populations are doing well, providing long term hope for reintroduction one day
Mass Extinction
While it's fortunately quite rare, there have been periods in our planets history where extinction has happened on a massive scale. Called mass extinctions, the most widely known of these events was the asteroid strike that wiped out the dinosaurs. However, mass extinctions can also be triggered by things like volcanic eruptions, or rapid shifts in climate, amongst other factors.
Did you know that earth has actually gone through five mass extinctions? Collectively, they're called the Big Five:
According to many scientists, we may in fact be entering a sixth mass extinction, and for the very first time it's being driven by a single species; us. According to data provided by the 2019 global assessment by IPBES, hundreds of species are being lost way faster than the average rate. While we've not managed to reach the enormity of the big five, the current rate makes it clear we could reach it within centuries if we don't do something to stop it.
The Five Major Reasons For Extinction
Generally, if a species goes extinct there's usually more than just one reason why. In fact, scientists have grouped the main causes for extinction into five major drivers which we'll speak about in more depth below.
Habitat loss
On land, habitat loss is without the biggest threat to wildlife. In general, most species have evolved skills to suit a particular habitat (like wetlands or decidious forest) and without these conditons they struggle to survive. Overall, the main culprits for habitat loss are logging, mining, roads, and the spread of towns and cities. Addtionally, even if a tiny bit of habitat survives, it’s often broken into small, isolated patches (known as fragmentation). Any animals trapped in these areas will naturally struggle to find enough food or mates, resulting in their populations taking a nosedive.
Depressingly, this great apes home is rapidly being cleared for palm oil plantations. Without rainforests, orangutans need to stay on te ground where they struggle to survive and find fruit and other suitable food.
When a habitat shrinks, a species may need to:
Overexploitation
Simply put, exploitation refers to taking wild plants and animals faster than they can breed and replace themselves and is a real problem in the oceans. For example, things lile overfishing, hunting for food, logging, and even the illegal wildlife trade all fall under this bracket.
While very few people actually need to go out and hunt their own food to survive, poaching for various valuable parts like the ivory and pangolin scales remains a serious and complicated problem. Additionally, without rules in place, industrial fishing ships can also rapidly strip entire fish stocks in an area in just a few years.
Passenger Pigeon
Look up into the sky back in the 1800's in America and there was a very high chance you'd see this bird flocking in the thousands. Sadly, relentless hunting for meat saw this birds population go from an estimated billion birds to zero by the time the last bird (named Martha) died in the Cincinatti Zoo in 1914.
Stellar's Sea Cow
This incredible giant sized relative of the Manatee was discovered by european hunters back in 1741. By 1768, only a mere 27 years later, the Stellar Sea Cow was completely gone - hunted to extinction for the sizeable profit its blubber and hide made hunters.
Climate Change
Humans burn a tremendous amount of fossil fuels every year which has increased the levels of carbon dioxide in the atmosphere. As the planet warms, habitats crucial to wildlife undergo changes which leaves certain species unable to adapt. For example, animals living in very specialised habitats like mountaintops or polar ice essentially have no where else to go.
How Climate Change Impacts Wildlife
- 1. Rising temperatures make it extremely difficult for species to survive in conditions they once thrived in
- 2. Melting sea ice all but removes the hunting grounds of animals such as polar bears, which end up swimming further and further to find the seals they prey on
- Rising sea levels also flood places like lying coasts and islands, permantly changing the habitats
- Warmer and more acidic oceans lead to coral reefs becoming bleached due to the absorbtion of carbon dioxide, leading to species like shellfish struggling to create suitable shells
- Lastly, shifting seasons affect the timing of things like breeding cycles and migration
Yes, The Bramble Cay Melomys which was found on a single tiny island in the Great Barrier reef of Australia. Sadly, several factors caused by climate change, incudling rising seas and frequent storm surges repeatedly flooded its home, leading to it officially being delcared extinct in 2019. It is the first mammal to be recorded becoming extinct due to climate change.
Pollution
Pollution is insidious, poisining the water, air, and soil that many species including mammals, birds, and insects depend on. While some pollution is easy to see, like plastic waste being washed up on the shore of beaches, other types are more invisible, such as harmful chemicals that slowly build up in the bodies of animals over time.
Pesticides
Many chemicals used to deal with pests can also seriously harm bees, birds, and other forms of wildlife.
Plastics
Mistaking plastic for food like jellyfish, seabirds and turtles commonly become sick from digesting it or get tangled up in it.
Nutrient run-off
When fertilizer runs into rivers and seas it causes algae to bloom. When they eventually die and rot, oxygen in the water is depleted creating dead zones where no species can survive.
The Story of DDT
During the 20th century, the pesticide DDT resulted in the eggs of birds of prey becoming so thin they broke during incubation. Due to this, populations of raptors like the Peregrine Falcon (the fastest bird in the world) began to collapse both in the States and the UK. Fortunately, DDT was quickly banned and the birds slowly but surely began to bounce back to healthy numbers.
Invasive Species
With the expansion of humans all across the world, many types of plants and animals have been transported to places they wouldn't normally reside in - sometimes by accident, sometimes on purpose. Unfortunately, not all introduced species of animals are good for their new found environment, and certain invasive species with no natural predators can quickly begin to run riot. Not only may they outcompete native species for food, but they can also prey on them and spead new diseases too. In fact, according to research by IPBES, invasive species were a major factor in around 60% of recorded animal and plant extinctions.
| Invasive species | Native range | Introduced location | Environmental impact |
|---|---|---|---|
| Grey squirrel | North America | United Kingdom | Competes with red squirrels and carries squirrelpox virus, which can be fatal to red squirrels. |
| Japanese knotweed | East Asia | United Kingdom and Europe | Forms dense stands that displace native vegetation and reduce plant diversity. |
| Cane toad | Central and South America | Australia | Its toxins kill some native predators that attempt to eat it. |
| Zebra mussel | Black Sea and Caspian Sea region | North America | Displaces native mussels and alters aquatic food webs through filter feeding. |
| Yellow-legged Asian hornet | Parts of Asia | Europe | Preys on honeybees and other insects, adding pressure to local pollinators. |
| Brown tree snake | Australia, New Guinea and nearby islands | Guam | Has caused the local extinction of several native forest bird species. |
| Water hyacinth | Tropical South America | Parts of Africa and Asia | Dense floating mats block light and can lower dissolved oxygen, harming aquatic ecosystems. |
Why Are Smaller Populations at Bigger Risk?
All five factors mentioned so far have the same affect: shrinking populations. Once a population shrinks too much, helping it to recover becomes a much harder task regardless of weather the original problem or threat is removed. For example, with smaller populations comes inbreeding which results in offspring eventually being born with health issues. Likewise, a single outbreak of a disease or even bad weather like a sudden drought or wildfire can wipe out the few remaining members of a species entirely (a major risk on islands).
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