Index of Biological Integrity (IBI)
The
Index of Biological Integrity, or IBI, is a scoring system used to measure strong responses to human disturbance, or pollution,
in wetlands. WHEP focuses on two biological communities: plants and macroinvertebrates (small organisms in the water
without a backbone: insects, leeches, snails, etc.).
The Minnesota Pollution Control Agency selected a variety of metrics (measurements)
which focus on those organsims which best reflect wetland quality or health. Each metric is evaluated based on the identified
specimens and their abundance. They reflect organism presence and relative abundance. Depending on the result of the
metric, each is awarded a score of one, three or five. The scores for each metric are combined to calculate a total
score, this is the IBI. The higher the score, the higher the likelihood of a healthy wetland.
The IBI score
is then converted to an overall rating to give the wetland a qualitative description (poor, moderate, excellent). A wetland
described as poor has a minimal variety of organisms and a large number of them would likely not be sensitive
to pollution. A wetland of excellent quality would have a higher variety of organims and contain those species
that are more sensitive to human disturbance or pollution.
The two IBIs (macroinvertebrates
and vegetation) have slightly different ratings based on the scoring range. This is due, in part, to the number of metrics
evaluated in each IBI; six for the macroinvertebrate and seven for the vegetation IBI.
Refer to the links below for a complete list and
description of the metrics used in the macroinvertebrate and vegetation IBIs.
