link to page 2 
July 8, 2021
Biodiversity
Biodiversity refers to the variety of life on Earth, and
million and 15 million, though estimates have ranged from
definitions of biodiversity generally encompass measures of
below 5 million to over 100 million species.
diversity at the genetic, species, and ecosystem levels.
Assessing changes in biodiversity—including both losses
In addition to assessing species diversity, biodiversity often
and gains—at all three of these levels and the causes, or
incorporates concepts of genetic and ecosystem diversity.
drivers, of these changes is of interest to many scientists
Genetic diversity is a measure of genetic variation among
and other stakeholders. Addressing biodiversity, including
individuals of the same species. Ecosystem diversity is a
biodiversity loss and the potential consequences for
measure of the variety of ecosystems, defined as the
humans, is also of interest to some Members of Congress.
community of organisms and their physical environments
Some Members have introduced legislation in the 117th
interacting together, in a given location.
Congress that aims to conserve species and ecosystems.
Changes in Biodiversity
Definition of Biodiversity
The number of species on Earth is not static, and
There are many definitions of biodiversity. Many
extinctions and speciation constantly occur through natural
include similar concepts to the definition provided by
processes. Humans also influence biodiversity, and many
the United Nations Convention on Biological Diversity
scientists assert that biodiversity is currently being lost at a
(CBD): biological diversity is “the variability among living
rate unprecedented over human history. Some counter this
organisms from al sources including, inter alia,
assertion by arguing that extinction is part of evolution and
terrestrial, marine and other aquatic ecosystems and
that all species are somewhere on the road to extinction;
the ecological complexes of which they are part; this
they note that there have been five mass extinctions in
includes diversity within species, between species and
Earth’s history without anthropogenic pressure.
of ecosystems.” Some definitions also consider
Status of Biodiversity
fluctuations to levels of biodiversity. For example, the
Intergovernmental Science-Policy Platform on
The IPBES published a 2019 study on global biodiversity
Biodiversity and Ecosystem Services (IPBES) definition
that assessed past, present, and potential future trends in
of biodiversity includes both concepts of biotic variety
biodiversity and ecosystem services. In the study, scientists
and “changes in abundance and distribution over time
found that societal effects on land, freshwater, and oceans
and space within and among species, biological
have accelerated in the past 50 years and are contributing to
an increase in the number of species threatened with
communities and ecosystems.”
extinction and the alteration of ecosystems and the services
they provide to humans. Some scientists, however, argue
Biodiversity decline is a concern for many stakeholders and
that changes in biodiversity at the global scale may not
policymakers due to the relationship between biodiversity,
reflect changes at the local scale, where biodiversity could
ecosystem services, and human welfare. For example,
be stable or increasing in some regions.
agricultural crops can be derived from wild species; plants
are often sources of natural medicines and contribute to
By analyzing the proportion of known species currently
prescription drug development (e.g., the rosy periwinkle
threatened by extinction (see Figure 1), the IPBES
found in Madagascar is the basis for medicine treating
extrapolated that roughly 1 million species—including both
Hodgkin’s disease and childhood leukemia); wildlife
known and unknown species—could be threatened with
provides essential nutrition and recreation; and ecosystems
extinction. The IPBES estimated that 25% of noninsect
provide services for humans (e.g., flood control, carbon
plants and animals and 10% of insects, which account for
sequestration, pollination, and water filtration).
75% of all species, could be threatened with extinction; it
Measuring Biodiversity
used 8.1 million as the estimate for total species. Some
stakeholders contend this figure may be overinflated,
How many species of plants, animals, fungi, and
because it is based on an inflated estimate of the total
microorganisms exist on Earth is a fundamental, yet
number of species on Earth. Other research also has
complex, question. As it is not currently possible to
quantified currently threatened species and potential
quantify every living species, scientists have used
biodiversity loss, though these findings have varied in
extrapolations to estimate total species richness. Due to
extent and severity. For example, one study estimated that
different scientists’ different methods and assumptions,
nearly 40% of wild plants were threatened with extinction.
estimates for the number of species on Earth have varied,
Another study estimated that some vertebrates’ population
sometimes widely. To date, scientists have directly
sizes had declined by an average of 68% over the last five
described approximately 1.5 million species. Many
decades. Further, a 2017 study concluded that, out of 177
estimates place the actual number of species between 8
https://crsreports.congress.gov
Biodiversity
mammal species studied, more than 40% had experienced
“severe population declines.”
Figure 1. Endangerment of Selected Groups of Species
Source: IPBES, Summary for Policymakers of the Global Assessment Report on Biodiversity and Ecosystem Services, 2019, p. 26.
The IPBES assessment also reported that ecosystems’
resources. There are 196 parties to the CBD; the United
ability to provide services is declining. For example, the
States is not a party. Other international agreements address
assessment stated that human beings have severely altered
biodiversity, including the International Union for the
75% of the land-based environment and approximately 66%
Conservation of Nature and the Convention on International
of the marine environment, which has resulted in a decline
Trade in Endangered Species of Wild Fauna and Flora.
of ecosystem services. The assessment noted that, absent
transformative changes, the negative trends in biodiversity
The United States does not have a federal program to
and ecosystem function and services are expected to
address biodiversity holistically, and there is no national
biodiversity assessment for the United States. Several
continue through 2050 and beyond.
federal agencies track and compile data on certain species
Drivers That Affect Biodiversity
and ecosystems, including the U.S. Geological Survey and
Several factors may affect biodiversity. The IPBES
U.S. Fish and Wildlife Service (FWS), among others.
assessment stated that changes in land and sea use, direct
Internationally, the United States provides funding for
exploitation of organisms , climate change, pollution, and
biodiversity through several international conservation
invasion of alien species all can lead to declines in
programs run primarily through the U.S. Agency for
biodiversity. Another study linked declining marine
International Development and FWS.
biodiversity with overfishing and climate change. The
Role of Congress
IPBES and the Intergovernmental Panel on Climate Change
reported that climate change also alters biodiversity and can
Some in Congress argue that existing U.S. laws and policies
exacerbate the negative effects of other drivers.
are sufficient to address biodiversity issues. Others call for
new authorities or additional funding to address these
Some scientists argue that land use change, including
issues. Stakeholders and policymakers note several avenues
agricultural expansion and deforestation, is the primary
that Congress might consider:
driver of biodiversity decline. For example, the IPBES
assessment found that over one-third of the world’s land
Conducting oversight over the implementation and
surface and three-fourths of its freshwater resources are
funding of existing laws and programs that address
dedicated to crop or livestock production.
biodiversity, such as the Endangered Species Act
Establishing a biodiversity program to holistically
Some scientists note that certain drivers could benefit
address biodiversity in the United States that includes a
biodiversity. For example, one study found that non-native
biodiversity strategy, as called for in H.Res. 69 in the
plant species may contribute to biodiversity. Other
117th Congress, and a national biodiversity assessment
scientists note that climate change may alter ecosystems
and may result in species geographically shifting, which
Considering ratifying the CBD and other agreements,
could increase biodiversity in some locations.
such as the Convention on Migratory Species
Enacting and funding the America the Beautiful
Global and U.S. Efforts to Address Biodiversity
initiative, which aims to conserve at least 30% of U.S.
Global efforts to address biodiversity are organized, in part,
lands and waters by 2030
under the CBD. The CBD’s main objectives are conserving
biological diversity, sustainably using components of
Enacting biodiversity-related legislation in the 117th
Congress, such as the Critically Endangered Animals
biological diversity, and ensuring the fair and equitable
sharing of benefits arising from the use of genetic
https://crsreports.congress.gov
Biodiversity
Conservation Act of 2021 (H.R. 1569 ) and the Protect
Kezee Procita, Senior Research Librarian
the Global Amphibians Act (H.R. 2026)
R. Eliot Crafton, Analyst in Natural Resources Policy
IF11871
Pervaze A. Sheikh, Specialist in Natural Resources Policy
Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff to
congressional committees and Members of Congress. It operates solely at the behest of and under the direction of Congress.
Information in a CRS Report should not be relied upon for purposes other than public understanding of information that has
been provided by CRS to Members of Congress in connection with CRS’s institutional role. CRS Reports, as a work of the
United States Government, are not subject to copyright protection in the United States. Any CRS Report may be
reproduced and distributed in its entirety without permission from CRS. However, as a CRS Report may include
copyrighted images or material from a third party, you may need to obtain the permissio n of the copyright holder if you
wish to copy or otherwise use copyrighted material.
https://crsreports.congress.gov | IF11871 · VERSION 1 · NEW