Did we really wipe out thousands of animal species?
A recent study reveals that human activities may have led to the extinction of hundreds of thousands of animal species since 1500. The International Union for Conservation of Nature (IUCN) Red List has put the confirmed figure at 777 during this period. However, this only represents around 5% of the world's known species assessed by the IUCN. Robert Cowie, a professor at the University of Hawaii was the lead author of the study.
Methodology behind the calculation
Cowie's team arrived at these figures by studying a random sample of 200 land snails and determining how many had gone extinct. They then applied this extinction rate to all known species over a 500-year period. The extinction rate they calculated was between 150 to 260 extinctions per million species-years (E/MSY). Cowie also compared these figures with extinction estimates for other wildlife groups, finding that estimates generally hovered around about 100 E/MSY.
Estimating extinctions among known/unknown species
Applying the extinction rate of 100 E/MSY to Cowie's method suggests that around 100,000 of the approximately two million known species have gone extinct over the past 500 years. However, this figure does not account for unknown animal species. A separate study published in PLOS Biology in 2011 claimed there are around 7.7 million animal species. Taking into account this figure, this results in an estimated total of around 381,150 animal extinctions caused by humans in over 500 years.
Challenges in calculations
John Alroy, an associate professor in the Department of Biological Sciences at Macquarie University in Australia, warns that it's virtually impossible to calculate modern extinction rates accurately. He advises caution when interpreting these figures, stating "We should be supercautious about trying to nail a number down based on the existing literature." Alroy emphasizes that understanding the overall extinction rate requires knowledge of how many species exist initially, a fact often unknown due to understudied regions and poorly understood animal groups.
Human impact on rising extinction rates
Despite the challenges in calculating exact extinction rates, both Alroy and Cowie agree that human activities have significantly worsened the situation. Alroy asserts that the number of extinctions is much higher than the 777 recorded on the IUCN Red List. Cowie echoes this sentiment, stating "whether the extinction rate is 100 E/MSY or 20 E/MSY or 200 E/MSY, it's still a lot and it's still really bad." This consensus underscores the urgent need for conservation efforts to mitigate human-induced extinctions.
