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1 1 (July 8, 2021)

handle is hein.crs/govedyn0001 and id is 1 raw text is: C r~ps~ion~I ~s~sr~h $arvk~a ~ ~ 9 July 8, 2021 Biodiversity Biodiversity refers to thevariety of life on Earth, and definitions of biodiversity generally encompass measuies of diversity at thegenetic, species, andecosystemlevels. Assessing changes in biodiversity-including both losses and gains-at all three ofthese levels and the causes, or drivers, ofthese changes is ofinterestto many scientists and other stakeholders. Addressing biodiversity, including biodiversity loss and the potentialconsequences for humans, is also ofinterestto some Members of Congress. Some Members have introduced legislationin the 117'h Congress that aims to conserve species and ecosystems. Definition of Biodiversity There are many definitions of biodiversity. Many include similar concepts to the definition provided by the United Nations Convention on Biological Diversity (CBD): biological diversity is the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems. Some definitions also consider fluctuations to levels of biodiversity. For example, the Intergovern mental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) definition of biodiversity includes both concepts of biotic variety and changes in abundance and distribution over time and space within and among species, biological communities and ecosystems: Biodiversity decline is a concern for many stakeholders and policymakers due to the relationship between biodiversity, ecosystemservices, and human welfare. Forexample, agricultural crops canbe derived fromwild species;plants are often sources of natural medicines and contribute to prescription drug development (e.g., theros y periwinkle found in Madagascar is the basis for medicine treating Hodgkin's disease and childhood leukemia); wildlife provides essentialnutrition and recreation; and ecosystems provide services forhumans (e.g., flood control, carbon sequestration, pollination, and water filtration). Measuring Biodiversity How many species of plants, animals, fungi, and microorganisms exist on Earth is a fundamental, yet complex, question. As it is not currently possible to quantify every living species, scientists have used extrapolations to estimate total species richness. Due to different s cientis ts' different methods and assumptions, estimates for the number of species on Earth have varied, sometimes widely.To date, scientistshave directly described approximately 1.5 million species. Many estimates place the actual number ofspecies between 8 million and 15 million, thoughestimates have ranged from below 5 million to over 100 million species. In addition to assessing species diversity, biodiversity often incorporates concepts of genetic and ecosystemdiversity. Genetic diversity is a measure of genetic variation among individuals of the same species. Ecosystem diversity is a measure of the variety of ecosystems, defined as the community of organisms and their physicalenvironments interacting together, in a given location. Changes in Biodiversity The number of species onEarth is not static, and extinctions and speciation constantly occur through natural processes. Humans also influence biodiversity, andmany 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 ofevolution and that all species are somewhere on the road to extinction; they note thatthere have been five mass extinctions in Earth's history without anthropogenic pressure. Status of Biodiversity The IPBES published a 2019 study on globalbio diversity that as sessedp ast, present, and potential future trends in biodiversity and ecosystems ervices. In the study, scientists found that societal effects on land, freshwater, andoceans have accelerated in the p ast 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 bio diversity could be stable or increasing in some regions. By analyzing the proportion of known species currently threatened by extinction (see Figure 1), the IPBES extrapolated that roughly 1 million species-including both known and unknown species-couldbe threatened with extinction. The IPBES estimated that 25% ofnoninsect plants and animals and 10% of insects, which account for 75% of all species, could be threatened with extinction; it used 8.1 million as the estimate fortotal species. Some stakeholders contend this figure may be overinflated, because it is based on an inflated estimate of the total number of species on Earth. Other research also has quantified currently threatened species and potential biodiversity loss, though these findings have varied in extent and severity. For example, one study es timated that nearly 40% of wild plants were threatened with extinction. Another study estimatedthat some vertebrates' population sizes had declinedby an average of 68% over the last five decades. Further, a 2017 study concluded that, outof 177 https://crsrepc

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