According to the International Union for Conservation of Nature (IUCN), as of 2021, there were 902 extinct species listed in their Red List of Threatened Species. The IUCN Red List is a comprehensive assessment of the conservation status of species, but it does not include all species on Earth.
The World Wildlife Fund (WWF) estimates that the current extinction rate is 1,000 times higher than the natural background extinction rate, which means that about 1,000 species are becoming extinct each year. This number might not represent all extinctions, as some may not be detected or recorded.
A study published in the journal "Science Advances" in 2019 suggested that the Earth is currently experiencing the sixth mass extinction event, which is caused by human activities. The study estimated that the extinction rate for land animals has increased 100- to 1,000-fold in the past century.
It's important to note that extinction is a natural process, but the current rate of extinction due to human activities is considered alarming, as it significantly impacts biodiversity and the functioning of ecosystems. Conservation efforts, habitat preservation, and sustainable practices are crucial in preventing further species extinctions.