In leppott/BCGcalc: Biological Condition Gradient, calculator

knitr::opts_chunk$set(echo = FALSE
                      , results = 'asis'
                      , warning = FALSE
                      , message = FALSE)

Purpose

The BioDiversity Index was developed for moderate to high gradient, low to mid-elevation streams in the Pacific Northwest Maritime Region with coarse mineral substrates and extensive erosional habitat. It can be used to help identify sites with high habitat complexity and resilience to disturbance that support macroinvertebrate communities with high and/or unique taxa richness representative of a BCG level 1 stream. During preliminary evaluations, there was good correspondence between Biodiversity Index scores and BCG model outputs (index scores followed the expected pattern, with highest median index scores occurring in BCG level 2 samples and lowest in BCG level 5-6 samples). Practitioners can use both tools together to help to identify sites that harbor exemplary biodiversity and help inform prioritization of sites for protection.

The BioDiversity Index is a multi-metric index calculated with the metrics and scoring criteria shown in Table 1, and the accompanying narrative ratings in Table 2. For more information, view this PDF and contact Bob Wisseman ([e-mail]).

Table 1. BCG Level 1 Biodiversity Index (draft, version 1) - community composition metrics and scoring thresholds.

Scoring criteria (points )

|Metric | 0 | 1 | 2 | 3 | |:-------------------------------|:---:|:-------:|:------:|:----:| |Total taxa richness |<40 |40-49 |50-59 | ≥ 60| |EPT taxa richness |<20 | 20-24 |25-29 | ≥ 30| |BCG attribute 1i, 1m & 2 taxa |<2 | 2-5 |6-8 | ≥ 9| |Shannon-Weaver diversity (logex)|<2.75|2.75-2.99|3.0-3.24|≥ 3.25| |Long-lived taxa richness |<6 |6-8 |9-11 | ≥ 12| |Ephemerellidae taxa richness |<3 | 3 | 4 | ≥ 5| |Heptageniidae taxa richness |<3 |3 | 4 | ≥ 5| |Nemouridae taxa richness |<3 |3 |4 | ≥ 5| |Perlidae taxa richness | <1 | 1 | 2 | ≥ 3| |Rhyacophila taxa richness | <3 |3-4 | 5 | ≥ 6| |Predator taxa richness |<10 |10-12 |13-15 | ≥ 16|

Noteworthy taxa richness Add an additional score point for each noteworthy taxa present

Table 2. BCG Level 1 Biodiversity Index (draft, version 1) – overall scores and ratings, as well as recommendations.

|Rating |Score |Description| |:------|:------|:----------| |High |≥ 30 | Exemplary biodiversity and high habitat complexity and resilience probable. Acquire additional information and data on the site and watershed that is readily available. Alert stakeholders, including government and non-government organization conservation agencies.| |Medium |21-29 | Moderate habitat complexity/resilience and biodiversity indicated. Further evaluation of the site and watershed is recommended.| |Low |<20 | Unexceptional biodiversity indicated. Mostly widespread and common taxa present.|

Test File

Click here to download example R scripts and data (all functions).

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Last updated 2023-08-16

leppott/BCGcalc documentation built on May 17, 2024, 5:55 p.m.