When the term biodiversity is used, it usually refers to the variety of living organisms on Earth and the ecosystems they form. Humans rely on biodiversity for food, water and other necessities of life, as well as a wide range of cultural and recreational activities. Biodiversity provides an important source of scientific information about the natural world and its origins, and it contributes to sustainable development in many ways. But it is also becoming increasingly clear that the extinction of species and the degradation of ecosystems threaten human survival.

Humans are rapidly changing the planet’s natural habitats, triggering a global loss of biodiversity at an unprecedented pace. Major direct threats to biodiversity include habitat loss and fragmentation, unsustainable resource use, invasive species, pollution, and global climate change. These changes are occurring at a time when the world’s population is growing and demands on the natural environment are increasing. Moreover, the impacts of global climate change are intensifying and compounding these other pressures.

Despite its importance, biodiversity remains poorly understood. This lack of understanding is partly due to a difficulty in agreeing on how to define biodiversity. A number of different definitions exist, and even within conservation biology the term is often defined differently from one author to the next. A key problem is that biodiversity consists of a diverse set of interrelated factors, making it difficult to isolate and measure its individual components.

In addition, biological diversity encompasses a broad spectrum of activities, from genes to ecosystems, and these functions are complex and highly interrelated. As such, the value of biodiversity is derived from the whole and not simply the sum of its parts. For example, the symbiotic relationship between plants and their pollinators provide crucial support services such as primary production of new organic material, cycling of nutrients essential for growth, and reproduction. Without these critical supports, life would grind to a halt.

Scientists are also discovering that biodiversity is essential to the functioning of all ecosystems, including our own. A recent study found that greater species diversity in animal communities tends to decrease the occurrence of disease. This is because disease-causing pathogens, like viruses or bacteria, are more likely to be defeated by genetically dissimilar organisms in a diverse community.

Millions of people rely on biodiversity for their livelihoods. Whether in a rural village in Kenya or a bustling city in Beijing, people are dependent on the many benefits that biodiversity provides. These benefits include water, fresh air, food, medicines and fuel sources. People are also dependent on biodiversity for spiritual and recreational reasons. For example, a visit to a forest or a beach can improve mental health and lower blood pressure. Furthermore, spending time in nature has been linked to increased life satisfaction and happiness. Nature-related tourism is also an important income generator for poorer nations. The preservation of biodiversity is therefore a vital economic and social imperative for humanity.