Biological integrity
Biological integrity is associated with how “pristine” an environment
Natural environment
The natural environment encompasses all living and non-living things occurring naturally on Earth or some region thereof. It is an environment that encompasses the interaction of all living species....

 is and its function relative to the potential or original state of an ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

 before human alterations were imposed. Biological integrity is built on the assumption that a decline in the values of an ecosystem's functions are primarily caused by human activity or alterations. The more an environment and its original processes are altered, the less biological integrity it holds for the community
Community (ecology)
In ecology, a community is an assemblage of two or more populations of different species occupying the same geographical area. The term community has a variety of uses...

 as a whole. If these processes were to change over time naturally, without human influence, the integrity of the ecosystem would remain intact. The integrity of the ecosystem relies heavily on the processes that occur within it because those determine what organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...

s can inhabit an area and the complexities of their interactions.


The concept of biological integrity first appeared in the 1972 amendments to the U.S. Federal Water Pollution Control Act, also known as the Clean Water Act
Clean Water Act
The Clean Water Act is the primary federal law in the United States governing water pollution. Commonly abbreviated as the CWA, the act established the goals of eliminating releases of high amounts of toxic substances into water, eliminating additional water pollution by 1985, and ensuring that...

. The United States Environmental Protection Agency
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...

 (EPA) had used the term as a way to gauge the standards to which water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 should be maintained, but the vocabulary instigated years of debate about the implications of not only the meaning of biological integrity, but also how it can be measured. The first conference about the term occurred in March 1975 called "The Integrity of Water" and provided the first accepted definition of biological integrity (see below). In 1981, EPA assembled a field of experts from the U.S. Fish and Wildlife Service, academia, and its own staff to further refine the definition and identify key indicators
Biological indicators are species used to monitor the health of an environment or ecosystem. They are any biological species or group of species whose function, population, or status can be used to determine ecosystem or environmental integrity. An example of such a group are the copepods and other...

 to quantitatively measure biological integrity. The conference not only identified a definition, but also methods to evaluate the community, and they established that multiple sites should be used to determine the condition of the environment


Today, the accepted definition is “the capability of supporting and maintaining a balanced, integrated, adaptive community of organisms having a species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 composition, diversity
Species diversity
Species diversity is an index that incorporates the number of species in an area and also their relative abundance. It is a more comprehensive value than species richness....

, and functional organization comparable to that of the natural habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...

 of the region.” This definition was adapted from Frey (1977). The implications of this definition are that living systems
Living systems
Living systems are open self-organizing living things that interact with their environment. These systems are maintained by flows of information, energy and matter....

 have a variety of scales relative to which they exist, that one can quantify the parts that sustain or contribute to a system's functioning and that all systems must be seen in the context of their environments and evolutionary history. This term primarily refers to aquatic environments
Aquatic ecosystem
An aquatic ecosystem is an ecosystem in a body of water. Communities of organisms that are dependent on each other and on their environment live in aquatic ecosystems. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems....

 because the vocabulary is derived from the Clean Water Act, but the concepts can be applied to other ecosystems.

Evaluation methods

In order to quantify and evaluate the biological integrity of a system, the Index of Biological Integrity
Index of biological integrity
An Index of Biological Integrity , also called an Index of Biotic Integrity, is a scientific tool used to identify and classify water pollution problems...

was created. In this index the baseline biological integrity (its function before human influence) and the current functions of an ecosystem are measured against one another to evaluate how much of ecosystem’s function has been preserved. The IBI evaluates the ecosystem by utilizing biosurvey
A biosurvey, or biological survey, is a scientific study of organisms to assess the condition of an ecological resource, such as a water body.-Overview:...

s and comparing species richness
Species richness
Species richness is the number of different species in a given area. It is represented in equation form as S.Species richness is the fundamental unit in which to assess the homogeneity of an environment. Typically, species richness is used in conservation studies to determine the sensitivity of...

, indicator taxa
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...

, hybrids, and invasive species
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....

. IBIs are used primarily to evaulate aquatic ecosystem
Aquatic ecosystem
An aquatic ecosystem is an ecosystem in a body of water. Communities of organisms that are dependent on each other and on their environment live in aquatic ecosystems. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems....

s even though one could technically apply any measurement of biological integrity to any natural ecosystem.

External links

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