Background extinction rate

Definition

The background extinction rate refers to the natural, ongoing rate at which species go extinct over long periods of time, typically measured in number of species per million species per year. This rate is a baseline against which mass extinctions can be compared, helping scientists understand the severity and impact of these larger events. It reflects the normal turnover of species due to various natural processes, including environmental changes, predation, competition, and habitat loss.

5 Must Know Facts For Your Next Test

1. The background extinction rate is estimated to be about 1 to 5 species per million species per year, which provides a frame of reference for understanding mass extinctions.
2. Mass extinctions are characterized by extinction rates significantly higher than the background extinction rate, often exceeding 75% of all species within a short geological period.
3. The current biodiversity crisis is causing extinction rates to rise dramatically above the historical background levels, often referred to as the sixth mass extinction.
4. Natural causes of extinction contributing to the background rate include climate changes, volcanic eruptions, and asteroid impacts that alter habitats and ecosystems over time.
5. Human activities have accelerated extinctions far beyond the background rate through habitat destruction, pollution, overexploitation, and introduction of invasive species.

Review Questions

• How does the background extinction rate provide context for understanding mass extinctions?
  • The background extinction rate serves as a baseline for comparing the scale and impact of mass extinctions. By knowing the typical rate at which species naturally go extinct, scientists can identify when an extinction event is occurring at an unusually high rate. This comparison allows researchers to assess the severity of biodiversity loss during mass extinctions and understand how these events differ from normal ecological processes.
• Discuss the factors that contribute to the background extinction rate and how they differ from those seen during mass extinction events.
  • The background extinction rate is influenced by natural ecological factors such as climate fluctuations, habitat changes, predation, and competition among species. These factors typically lead to gradual changes in species populations over long periods. In contrast, mass extinction events are often triggered by sudden catastrophic occurrences like asteroid impacts or extensive volcanic activity, resulting in widespread and rapid losses of biodiversity far exceeding the normal background rates.
• Evaluate the implications of rising extinction rates in relation to the background extinction rate and the potential for a sixth mass extinction.
  • The increasing extinction rates driven by human activity are raising alarms about a potential sixth mass extinction. As current rates soar well above historical background levels, it highlights not only the vulnerability of many species but also the urgent need for conservation efforts. If these trends continue unchecked, we could witness profound ecological disruptions that fundamentally alter ecosystems and reduce biodiversity on an unprecedented scale, with consequences that could impact humanity’s survival and well-being.

Related terms

mass extinction:

A significant and rapid decrease in biodiversity on Earth, marked by the extinction of a large number of species across multiple taxa in a relatively short geological time frame.

biodiversity:

The variety of life in the world or in a particular habitat or ecosystem, encompassing different species, genetic variations, and ecosystems.

extinction event: A widespread and rapid decrease in the biodiversity on Earth that results in the extinction of a large number of species within a relatively short geological period.