Earth has gone through five mass extinctions in 4.5 billion years. The first mass extinction occurred in the dim early history of life on Earth, when methane-breathing one-celled animals destroyed themselves by exhaling oxygen—a poison—into the atmosphere. Their descendants still live in our intestines and help us digest food. The first generally accepted Great Extinction took place approximately 440 million years ago, at the end of the Cambrian age, and nearly 85 percent of marine animal species were wiped out. Other mass extinctions eliminated 70 percent of life 370 million years ago, 95 percent 245 million years ago, and 23 percent 210 million years ago. The most recent one was 65 million years ago, resulting in the loss of approximately 85 percent of all species. Scientists currently believe, and have believed for many years, that Earth is facing its sixth Great Extinction, and it has the potential to become the most devastating one yet.

Each mass extinction—prior to this sixth one—have been caused primarily by climate changes or catastrophic events such as the large asteroid collision that wiped out the dinosaurs 65 million years ago. Scientists today believe that the sixth mass extinction is being caused by humans, and that its first phase started when human beings began to spread across the globe, approximately 100,000 years ago.

The second phase of this sixth extinction began 10,000 years ago, when humans began agriculture. Human beings began to live outside the ecosystem, and this has caused a devastating change in the world’s ecology. This second phase has recently become the most devastating, because it includes the Industrial Revolution, which has led to the destruction of rainforests, and the elimination of many different species.

Along with deforestation, the use of fossil fuels has also led to a drastic climate change. Today, 9 out of 10 species face extinction, due to the loss of their natural habitats and humans treating them as natural resources and killing them off instead of cultivating them. Although the extent of this sixth extinction have not reached the levels of the one 245 million years ago, concerned scientists and conservationists believe that the current rate of decrease in species will continue as long as humans continue their destructive behavior.

In previous mass extinctions, the destruction continued as long as the cause for the extinction was present. In the case of this sixth extinction, the cause of the devastation is us—human beings. If we continue to disregard the warning signs, then ultimately, we will be part of our own extinction, and then the process will stop.

Healthy ecosystems provide humans with clean air and valuable resources that are important to our everyday lives. Conservation efforts, modifications to the use of natural resources, and the stabilization of the human population has given some hope to those who are watching this mass extinction closely. We, as individuals, can help by changing our ways. As long as we make a collective effort, there still remains the possibility that life on Earth will be able to recover, and we can avoid becoming the next species on the endangered list.