The article discusses the widespread loss of animal species and populations, known as "defaunation," which is a major driver of global environmental change. Since the 1500s, 322 vertebrate species have gone extinct, and many others show significant population declines. Invertebrates also face severe declines, with 67% of monitored populations showing a 45% average decline. These losses have cascading effects on ecosystem functioning and human well-being. Defaunation is a key component of the sixth mass extinction and is driven by factors such as overexploitation, habitat destruction, and invasive species. Climate change is also emerging as a major threat. The impacts of defaunation are far-reaching, affecting ecosystem services like pollination, pest control, nutrient cycling, and water quality. It also influences human health by affecting disease transmission and food security. The loss of large animals has significant ecological consequences, including changes in plant-animal interactions and ecosystem functions. Defaunation also has evolutionary implications, as it can lead to changes in species morphology and life history traits. The article emphasizes the need for urgent action to mitigate defaunation, including reducing overexploitation and addressing climate change. It calls for a focus on predicting the patterns of winners and losers in the Anthropocene to better understand and manage the impacts of defaunation on ecosystems and human well-being.The article discusses the widespread loss of animal species and populations, known as "defaunation," which is a major driver of global environmental change. Since the 1500s, 322 vertebrate species have gone extinct, and many others show significant population declines. Invertebrates also face severe declines, with 67% of monitored populations showing a 45% average decline. These losses have cascading effects on ecosystem functioning and human well-being. Defaunation is a key component of the sixth mass extinction and is driven by factors such as overexploitation, habitat destruction, and invasive species. Climate change is also emerging as a major threat. The impacts of defaunation are far-reaching, affecting ecosystem services like pollination, pest control, nutrient cycling, and water quality. It also influences human health by affecting disease transmission and food security. The loss of large animals has significant ecological consequences, including changes in plant-animal interactions and ecosystem functions. Defaunation also has evolutionary implications, as it can lead to changes in species morphology and life history traits. The article emphasizes the need for urgent action to mitigate defaunation, including reducing overexploitation and addressing climate change. It calls for a focus on predicting the patterns of winners and losers in the Anthropocene to better understand and manage the impacts of defaunation on ecosystems and human well-being.