Mass extinction of Earth's wildlife is closer than we think - study

Human destruction of global wildlife is occurring at an alarming rate, according to a new study published in the journal Biological Reviews last week. 

Defaunation, defined as "the global-scale decline of animal biodiversity" is a disturbing consequence of human life on Earth, the authors of the peer-reviewed study posited. 

Extinction has traditionally been tracked by the International Union for the Conservation of Nature's (IUCN) Red List conservation categories. 

IUCN Red List of Threatened Species

The IUCN Red List of Threatened Species was established in 1964 to be a widely-accessible and reliable indicator of the health of global biodiversity. Per the IUCN website, the Red List is used by government agencies, wildlife departments, conservation-driven nonprofits, educational organizations, students and businesses. It is also cited in peer-reviewed journal articles about wildlife conservation. 

According to the IUCN, approximately one-quarter of the world's animal species are under threat of extinction and about 1% have been declared extinct. However, the new study claims that the IUCN report does not show the full picture. 

Extinctions are preceded by progressive species population declines over time, which leave traces - "demographic footprints" that can alert scientists to the possibility of imminent extinction, study authors claim. Thus, only using IUCN data without considering population trends may result in a gross underestimate of how many populations are going extinct.  

Using population data from over 70,000 species of animals spanning all five vertebrate groups (mammals, birds, reptiles, amphibians, fish), study authors were able to demonstrate a large-scale erosion of species across the board. 

Per the data, 48% of species examined are currently undergoing population decline, 49% are stable and 3% are increasing. It was also found that 33% of species defined by the Red List as "non-threatened" are actually in decline.  

Extinction and how to protect endangered species 

Extinctions, per the study, are the result of a progressive population decline which eventually reaches a "tipping point" after which time it cannot recover.

"The circumstances that trigger the onset of these processes of decline can be multiple," explained authors, "but they have in common an alteration in the interactions between environmental conditions and the traits that species have evolved to face those conditions - i.e., when patterns of natural selection change at rates that exceed a species' ability to respond or adapt to such changes."

Tracking population changes can therefore prove an indispensable tool to predict the future of a species and can lend a much more nuanced understanding of a species' standing than a Red List categorization alone can provide.

Focusing on and publicizing the rate of biodiversity decline must be a universal priority, concluded the study. "Now is a critical time to increase effort toward preemptive conservation – protecting species before they become threatened." 

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