New Research Challenges Notion of Sixth Mass Extinction
A recent study has sparked a significant debate in the scientific community by challenging the widely accepted idea that humanity is currently experiencing a sixth mass extinction. This claim, which was previously supported by some researchers, suggests that the current rate of species loss is comparable to past mass extinctions that wiped out large portions of Earth’s biodiversity.
The study, published in the journal PLOS Biology, argues that while biodiversity loss is indeed a pressing issue, the rates at which species are disappearing do not meet the criteria for a mass extinction event. According to the research, mass extinctions are typically defined as the loss of 75% of all species over a relatively short geological time frame. So far, only five such events have occurred throughout Earth’s 4.5 billion-year history.
Key Findings of the Study
The analysis conducted by John Wiens, a professor of ecology and evolutionary biology at the University of Arizona, and his colleague Kristen Saban from Harvard University, focused on genus-level extinctions since 1500. A genus is a biological classification that groups different but related species, such as the genus Canis, which includes wolves, dogs, and coyotes.
According to the study, 102 genera have gone extinct in the past 500 years — 90 animals and 12 plants. The research also identified extinctions in two broader categories: 10 families and two orders. While the study did not focus on species-level extinctions, it noted that more than 900 individual species have gone extinct in the same period, according to IUCN data.
Island Habitats and Conservation Efforts
One of the key findings of the study is that most of these extinctions have occurred in island habitats, which are particularly vulnerable to invasive species introduced by human activity. Wiens pointed out that these extinctions may not be representative of a broader trend affecting mainland ecosystems.
The study also found that genus-level extinction rates appear to have begun declining, with the fastest extinction rates occurring in the 1870s, 1890s, and 1900s. This suggests that conservation efforts, especially for mammals and birds, may be having a positive impact.
Contrasting Views on Biodiversity Crisis
While the new study challenges the notion of a sixth mass extinction, it does not deny the ongoing biodiversity crisis. Many scientists agree that the current rate of species loss is alarming and poses a serious threat to ecosystems worldwide.
However, there is still debate about whether the current decline meets the threshold of a mass extinction event. Some researchers argue that the loss of species and genera is happening at a rate much higher than any other point in the last million years, while others believe that the current crisis is distinct from past mass extinctions.
Expert Perspectives
Sadiah Qureshi, a historian of science at the University of Manchester, emphasized the importance of distinguishing between the biodiversity crisis and a potential mass extinction. She noted that while the concept of a sixth mass extinction may serve as a call to action, it can also be counterproductive if it leads people to feel powerless.
Conrad Labandeira, a senior scientist at the Smithsonian National Museum of Natural History, agreed that the current biodiversity crisis exists, but he cautioned against equating it with a mass extinction. He stressed the need for continued conservation efforts to protect endangered species and their habitats.
Challenges in Documenting Extinctions
Stuart Butchart, chief scientist at BirdLife International, highlighted the difficulty of confirming extinctions, particularly among poorly studied groups such as invertebrates, plants, and fungi. He noted that understanding the full scope of species loss requires extensive research and careful documentation.
Butchart also expressed concern about the distraction caused by debates over whether a sixth mass extinction is imminent. He argued that the current extinction rates are already a cause for alarm and require immediate action to preserve biodiversity.
Conclusion
The debate over whether we are witnessing a sixth mass extinction underscores the complexity of assessing biodiversity loss. While the new study provides valuable insights into the patterns of extinction, it also highlights the need for continued research and conservation efforts to protect the planet’s rich diversity of life.
