Mass Extinction: An Introduction

This blog will discuss the causes and ramifications of mass extinction, and explore the debates surrounding the possibility of the onset of a sixth mass extinction. An understanding of the conditions preceding historical mass extinctions are important to our comprehension of the biological and evolutionary significance of our current climatic state on a potential forthcoming mass extinction.

As climatic conditions change, ecosystem variables shift, and environmental conditions alter, a certain number of species extinctions are likely to occur. Fossil evidence suggests that the majority of species have a lifespan of between 2 and 10 million years, this process of extinctions is considered to be ‘normal’. Although biodiversity loss occurs at a regional level, it influences the functioning of earth systems and leads to more wide reaching consequences. In contrast, mass extinctions can be defined as extinctions of a significant proportion of global biota in a geologically insignificant period of time (Sepkoski 1986).

Rockstrom et al (2009), amongst others, suggest that the current rate of extinction is between 0.2 and 0.5 per year per million species, somewhere between 100 and 1000 times greater than the ‘natural’ level. Discussion of the causes of mass extinctions, specifically whether they are due to climatic or anthropogenic influence will be tackled in later posts.

Mass extinction is a timely and relevant topic, and a rich source of academic debate. This blog will examine the complexities of mass extinction, and feels justified in doing so for the following reasons:

• A greater understanding of the causes of mass extinction will facilitate a more informed and committed approach to efforts to ensure the health of future ecosystems.
• Ocean feedbacks, and the development of their effects on life on earth, need to be understood in the context of mass extinctions.
• Levels of CO₂ and other greenhouse gases, the rates and causes of fluctuations, need further examination, as several theories suggest that they are contributing factors to mass extinction events.
• The level at which humanity can responsibly continue to make long-term social and economic developments needs to be understood in the context of biodiversity loss (Rockstrom et al 2009).