jbs Notes:
tasken with regard to Natural England
Biodiversity Metric 3.1: User Guide


biodversity units

Calculate the losses and gains in biodiversity unit value 
resulting from changes or actions which affect biodiversity, 
such as from development or changing the conservation management 
of a land holding;

Predict the likely effectiveness of creating new or enhancing 
existing habitats; and

Compare different plan and project proposals for a site 
allowing more objective assessments of alternative approaches 
to be made.

The outputs of the metric are only as robust as the quality of 
data and professional input into the metric.

Biodiversity units are calculated using the size of a parcel8 
of habitat and its condition.The metric uses habitat area 
(measured in hectares) as its core measurement, except for 
linear habitats (hedgerows, lines of trees, rivers and streams) 
where habitat length (measured in kilometres) is used.

A competent person must carry out the habitat survey and assessment. 
They should be able to confidently identify the positive and negative 
indicator species for the range of habitats likely to occur in a 
given geographic location at the time of year the survey is undertaken.

the quality component of each sccore is generated by an expert 
based on site data and professional judgement: values are high, medium, 
or low

assigns scores for identifid segments of land or stetches of 
linear components (e.g., streams, windrows)

habitat parcels - divide areas intodistinguishable parcels.

quality score - assign a score indicating distinctiveness,
conditions, strategic significance 

caorlculate number that is product of area sixe x quality score 
to produce biodiversity unit value

compute baseline value (pre-intervention) by aggregations

the  compute post-invervention, either based on projections or 
as actually recalculated after investion

difference betweenthe two is regarded biodiversity change and 
can be viewed as amount of enhancement

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as per 3.1 guide:

Chapert 2:

biodeversity based on ecological services aimed at human benefit (6)

numericals needed to inform decesion-makingand(6)

metric used to calculate biodeversity units (6)

used to calculate change - e.g., pre-and post-intervention (7)

to meassure loss and gain (8)

3.1 uses habitats -> biodiversity units ->
calculation: size of units or length -> scores 
(distintiveness, condition, strategic significance) (10 + 11)

also notes risks and losses with respect to other areas (10)

calculation tool used to calculate measure for each area
andto aggregate scores (11) 
multiplies area by 3 factor values (11)

calculates baseline pre-intervention vqlue to be compared with post-intervention value
to evaluate retained, lost, or enhanced value

tool also tracks risk score: (difficulty of oprating on habitat, temporary risk, spatial risk) (12)

3,1 model example calculation (13)
3.1 model example application (14)
3.1 model example project planning (15)

3,1 model calculations (16-18)

chapter 3:


A competent person must carry out the habitat survey and assessment.
Must be able to identify positive and negative ndicator species. (22)

strategic significance (28)

field notes examples (31)

chapter 4:
how to use the calculation tool (33 - 47)

calculation tool guide details/examples (34- 35)

chapter 5:
Detailed description of metric (48 - 63)

chapter 6:
biodiversity are habitat unit calculations (64 -71)

chapter 7:
urban trees (72 - 76)

chapter 8:
linear habitats - hedgerows (77 - 82)
chapter 9: 
linear habitats - rivers and streams (83 - 98)

chapter 10:
using 3.1 with other metrics (99 - 101)