Holocene extinction

The Holocene extinction is a major biological event occurring during our current geological epoch, the Holocene. It is characterized by a rapid loss of biodiversity across the planet. This event affects many different groups of living things. These include mammals, birds, reptiles, amphibians, fish, and invertebrates. It also impacts both terrestrial species on land and marine species in the ocean.

Many scientists refer to this as the Anthropocene extinction. This term highlights that human activity is the primary driver of these changes.

This extinction event works through several interconnected mechanisms. Anthropogenic climate change, or human-caused shifts in weather patterns, alters habitats. Deforestation and the destruction of wetlands remove the homes that animals need to survive.

Overfishing and the overexploitation of natural resources deplete populations of marine and land animals. Ocean acidification, caused by changes in seawater chemistry, harms many sea creatures. Human population growth and increasing economic consumption also put pressure on the natural world. These factors combine to create a crisis that disrupts the systems supporting life on Earth.

Scientists observe these losses in many different ways and stages. For example, the loss of plants has become more extensive in recent stages of the Holocene. This is often linked to land conversion and the clearing of forests. We also see the loss of specific animal groups, such as the decline of vertebrate populations. Some researchers note that even modest hunting pressure can cause entire species to vanish. This is especially true for large animals living on isolated islands.

History provides many examples of how these extinctions have unfolded. The dodo became extinct in the mid-to-late 17th century. This happened because of habitat destruction, overhunting, and the introduction of new mammals to its home. In the mid-15th century, the moa went extinct due to hunting and habitat loss by the Māori people.

Some researchers believe that even earlier humans may have contributed to extinctions in Australia, New Zealand, and Madagascar. These historical events help scientists understand the patterns of modern biodiversity loss.

Numerical data shows the scale of this current crisis. The contemporary extinction rate is estimated to be 100 to 1,000 times higher than the natural background extinction rate. The background rate is the typical speed of species loss through natural evolution.

Some controversial estimates suggest the rate could be as high as 10,000 times the background rate. A 2019 United Nations report estimated that about one million species are at risk. A 2023 study suggested that around two million species are threatened with extinction. This is double the estimate provided by the 2019 report.

Specific studies offer even more startling details about the state of life. A 2015 study on Hawaiian snails suggested that up to 7% of Earth's species might already be extinct.

A 2021 study found that only about 3% of the planet's land surface remains ecologically intact. This means most land has a significant human footprint. If global warming continues, studies suggest between 13% and 27% of terrestrial vertebrate species could be lost by 2100. Biologist Edward Osborne Wilson predicted that half of Earth's higher lifeforms could be extinct by 2100 if current trends continue.

There is an ongoing scientific debate regarding the classification of this event. Some scientists argue that we have not yet reached a full mass extinction. They suggest we are currently on the edge of one. Others assert that the planet has already entered the sixth mass extinction.

A 2022 study in Science Advances supports the idea that the sixth mass extinction is underway. This event is closely tied to the broader concept of the Anthropocene. This is a proposed new geological epoch defined by the massive influence of humans on Earth's systems. Understanding these connections is vital for studying the future of our planet.