Planet Earth is currently home to about 10 million species of plants, animals, fungi, bacteria, and other living things. That’s just an estimate: scientists have only named and classified about two million of those species.
All these species, large and small, work with other species to create thriving ecosystems. Healthy ecosystems provide ecosystem services. These services include clean drinking water, the food we eat, the wood we use to build our homes, medicines, and much more. Preserving biodiversity helps keep ecosystems healthy and healthy ecosystems help humans thrive!
What is Biodiversity?
Biodiversity is the amount and variety of life in a given area. This includes everything – microbes, fungi, plants, and animal species.
The amount of biodiversity varies from region to region. Tropical rainforests have the most biodiversity of any ecosystem on earth. That means that the rainforest biome supports more species and forms of life than anywhere else! A close second is coral reefs, where millions of marine species can live together.
One of the least biodiverse biomes is the tundra. Tundra is a cold habitat that stays frozen most of the year, doesn’t get much rain or sun, and has poor soils. Trees can’t grow on the tundra and the animals that live there often hibernate in the winter to conserve energy. There are very few species adapted to live in these harsh environments. This also means that places without biodiversity provide fewer ecosystem services.
When life began on earth, there were only a few single-celled organisms and almost no biodiversity. Our planet has grown more biodiverse as these organisms evolved into many different species. Now, the planet is full of millions of species!
There were several periods, however, when the earth lost most of its biodiversity. These periods are called mass extinctions.
What causes Mass Extinctions?
Mass extinction is defined as a period where 75% (or more) of the species on earth went extinct in a short period of time. Scientists have found evidence of five mass extinction events. These happened over thousands (or even millions) of years. That may sound like a long time, but, in geologic time, several million years is the blink of an eye.
The most famous mass extinction took place about 66 million years ago. The End Cretaceous Extinction marked the death of the dinosaurs. A large object hit earth from space and, at the same time, there were major volcanic eruptions. These events changed the climate dramatically. Dinosaurs couldn’t survive in the new conditions.
The End Cretaceous event is the most recent mass extinction in the fossil record. Other extinctions happened 450 million years ago, 375 million years ago, 252 million years ago, and 201 million years ago. All of these extinction events were caused by major disruptions to the climate, usually because of a meteor impact or large volcanic eruptions.
After a mass extinction, ecological niches (places where animals could live, eat and reproduce) open up for new species. Different types of plants and animals evolve to fill these niches. For example, after the dinosaurs died out, mammals grew larger and became dominant. The small number of dinosaurs that did survive evolved the ability to fly, that’s right, they are now birds!
Some species have survived through many extinction events. For example, the horseshoe crab first evolved about 450 million years ago, so it has survived four mass extinctions. That’s one tough crab!
The Sixth Mass Extinction
The earth is in a time of radical climate change right now. Humans, with our incredible technology like cars and factories, are currently releasing more carbon dioxide into the atmosphere. This carbon dioxide helps trap the heat from the planet and produces some truly crazy climate change events. For example, we now have more hurricanes than in the past, and they are getting stronger! We are also seeing much bigger wildfires due to severe droughts that climate change causes.
Some scientists believe that we are currently in the middle of the sixth mass extinction event. Many species can’t adapt quickly enough to changing conditions. In fact, dozens (or possibly hundreds) of species are going extinct every day! We haven’t even named some of them!
The only thing that is different this time is that humans are causing the changing climate – instead of an asteroid or volcanoes. The good news is that humans can take action to reverse climate change. If we act fast and have a bit of luck, we may be able to stop this mass extinction before it happens!
Together, all of these biotic elements and abiotic elements create an ecosystem.
Written by Laura McCamy
Edited by Gabriel Buckley, MS Professional Natural Sciences
Illustrated by Meimo Siwapon