This book focuses on biological diversity, or "biodiversity", which refers to the variety of all life on earth, and the complex relationships among living things, and between living things and their environment. Biodiversity includes genetic variety, species diversity, and variability in communities, ecosystems and landscapes. Biodiversity sustains the environments in which we live and on which our lives and those of every other living creature on Earth depend. Thanks to biodiversity, we are able to obtain such necessary goods as food, clothing, medicine, and fuel. Equally important are the ecosystem services that biodiversity provides, such as clean air and drinkable water. Conservation scientists have identified a number of universal threats to biodiversity: habitat loss and degradation, invasive species, pollution, overpopulation, overexploitation and consumption, and global climate change.