Biodiversity, also known as biological diversity, refers to the variety of life on Earth in all its forms, encompassing all the species that share a defined habitat to form a community of interdependence. From a taxonomy standpoint, estimates suggest that between 80 and 90 percent of the actual living species on Earth are undiscovered or unnamed, as per a 2009 report by IUCN from 2009.

Biodiversity influences the organization of communities at all levels, from soil teeming with microbial life to a pasture seeded with grasses and forbs, to mature tropical rainforests. It shapes the characteristics and capacities of every species and creates the conditions under which all living creatures interact and evolve.

Early scientistsCharles Darwin and Alfred Wallace recognized the importance of biodiversity for ecosystems, suggesting that a diverse mixture of crop plants should be more productive than a monoculture. Understanding biodiversity involves analyzing its operation in three distinct levels in natural systems: genetic, species, and ecosystem biodiversity. Ecosystems with greater biodiversity are better suited to withstand disturbance and to recuperate from adverse impacts. Communities with greater biodiversity generate more biomass, are more resistant to environmental disturbances, and regenerate more quickly after disturbances.

Some studies, such as those conducted by R.F. Noss, suggest a more complex approach, including four levels: genetic, species, community/ecosystem, and landscape. The landscape level refers to the spatial complexity of multiple communities/ecosystems and their interactions in a mosaic landscape. Community/ecosystem refers to the species living in a reasonably homogenous area or ecosystem and the relation between them. Species level refers to examining a specific species in total or a limited area. The genetic level refers to internal attributes and changes within a species. The four levels of biodiversity are divided into three attributes. Composition refers to the assortment and diversity of elements encompassing species and genetic diversity; structure includes the tangible organization and configuration of the system, and function includes ecological and evolutionary mechanisms such as gene disturbances and nutrient cycles. This classification demonstrates the interconnection between different factors and the complexity and dependence of biodiversity on the balance of these factors.

Human activities heavily affect biodiversity, both directly and indirectly. The five primary direct drivers of biodiversity loss, as identified by IPBES (2019), include changes in land and sea use, direct exploitation of organisms, climate change, pollution, and invasion of alien species. Various human activities lead to alteration, destruction, or fragmentation of natural habitats, change in ecosystems processes, impacting the survival, reproduction, and health of different species composing biodiversity at broader levels, such as ecosystems and landscapes.

Biodiversity integrity is a component of the Planetary Boundaries framework. The functioning of the biosphere ultimately relies on its genetic diversity, inherited from natural selection not only during its dynamic history of coevolution with the geosphere but also on its functional role in regulating the state of the Earth system. Of an estimated 8 million plant and animal species (IPBES 2019), around 1 million are threatened with extinction, and over 10% of genetic diversity of plants and animals may have been lost over the past 150 years. Thus, the genetic component of the biosphere integrity boundary is markedly exceeded.