Biodiversity refers to the variety of life on Earth, and definitions of biodiversity generally encompass measures of diversity at the genetic, species, and ecosystem levels. Assessing changes in biodiversity—including both losses and gains—at all three of these levels and the causes, or drivers, of these changes is of interest to many scientists and other stakeholders. Addressing biodiversity, including biodiversity loss and the potential consequences for humans, is also of interest to some Members of Congress. Some Members have introduced legislation in the 117th Congress that aims to conserve species and ecosystems.
The number of species on Earth is not static, and extinctions and speciation constantly occur through natural processes. Humans also influence biodiversity, and many scientists assert that biodiversity is currently being lost at a rate unprecedented over human history. Some counter this assertion by arguing that extinction is part of evolution and that all species are somewhere on the road to extinction; they note that there have been five mass extinctions in Earth’s history without anthropogenic pressure.
Scientists found that societal effects on land, freshwater, and oceans have accelerated in the past 50 years and are contributing to an increase in the number of species threatened with extinction and the alteration of ecosystems and the services they provide to humans. Some scientists, however, argue that changes in biodiversity at the global scale may not reflect changes at the local scale, where biodiversity could be stable or increasing in some regions.