The Earth Has Seen Five Major Mass Extinctions. Are We In The Sixth?

Many scientists fear that we're in the midst of a dangerous mass extinction event causing massive biodiversity loss, and without any action, humanity will be threatened.

Unfortunately, that's not the tagline for the latest disaster movie starring The Rock. It's a concern real enough that the United Nations just released an extensive plan to better protect the planet. The 20-point plan includes methods for cutting back on the pollution from plastic waste, converting more land to natural areas to maintain biodiversity and figuring out better ways to control invasive species.

The UN is hoping that policymakers will adopt this plan following a biodiversity conference in China in October.

If they don't, the loss of biodiversity can have a huge impact not just on the plants and animals across the planet, but also on humans. We rely on diverse ecosystems to pollinate and nourish the land we use to grow food and convert the sun's energy to give us clean air to breathe.

When those ecosystems are threatened by pollution, torn down by over-farming or construction of new cities or taken over by invasive species, those ecosystems crumble, piece by piece. Pollinator populations start to dwindle or go extinct completely, and without as much healthy land, other plants and animals that rely on nutrient-rich food sources start to suffer. Meanwhile, pollution harms or kills off other species, and shortens human lives. Taken together, these factors contribute to what scientists fear is the sixth mass extinction event in Earth's history.

There have been five major mass extinctions:

• End Ordovician: This went down a mere 444 million years ago, when most of the life on this planet was tiny sea creatures. Scientists believe that an intense ice age over about 1 million years killed about 86% of graptolites, a now-extinct aquatic creature.
• Late Devonian: About 375 million years ago, 75% of the planet's trilobites went extinct after a possible algae bloom that suffocated these aquatic bottom dwellers.
• End Permian: This was the worst of the mass extinctions so far. During what's known as "The Great Dying," the Earth lost 96% of tabulate corals, 70% of land vertebrates, and an incredible amount of insects and bacteria. It was likely at least partially caused by a volcanic event in Siberia.
• End Triassic: No one knows what caused this one, but it wiped out about 76% of marine and land species about 201 million years ago. This allowed dinosaurs to become the rulers of the Earth. At least until ...
• End Cretaceous: ... the End Cretaceous event, also know as the K-T event, a sudden extinction (likely caused by an asteroid) that killed about 80% of all plant and animal life on Earth.

Well, there is some debate about that among biologists. Some believe that the last millennia of humans occupying this planet has altered it in a way similar to mass extinctions in the past – by taking over, we're slowly but surely killing every plant and animal in the process and, in the end, ourselves. Others argue that the past five extinctions were far more extreme, and that what we're experiencing now doesn't quite qualify as one of those cataclysmic events.

But while there is disagreement on whether or not this is a scientifically defined mass extinction in the same way that the previous ones were, most biologists agree that better measures – such as those outlined by the UN – must be put in place to protect biodiversity.

Last year, a UN report found that a whopping 1 million species, or about one-eighth of all animals, are facing extinction. That's why they're hoping their latest report, which calls for cutting pollution in half and protecting at least 30% of the planet before 2030, will be accepted by those with the power to make the necessary changes.