In barely fifty years, wild animal populations have plummeted by more than 70 %. Behind this die off lies an unprecedented ecological crisis : runaway warming, habitat destruction, plastic pollution, over exploitation and invasive species. This book, based on the latest (2024-2025) data and on reliable international studies, provides an accurate picture of this alarming situation. It highlights the species most at risk (migratory fish, Arctic seals, birds) and analyses the drivers of their decline. Yet the work is not limited to a diagnosis : it shows that solutions exist and are already working. Success stories, such as the return of bison to Indigenous lands or the growth of tiger populations in Thailand, prove that a reversal is possible if emissions are reduced, ecosystems restored, poaching curbed and citizens mobilised. Clear and well documented, this essay invites readers to understand the reality of the ecological crisis and to act in defence of life.