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Biodiversity Target (B module)

Status: Not yet implemented in TargetEcon 2026. Present in other model versions.

var_B = 0 in the current model — the scalar exists but no constraints or equations activate when set to 1.

What it would do

A biodiversity target would add a constraint requiring a minimum area of habitat or nature measures — in addition to (or instead of) water quality targets. In the spirit of the model structure, it would likely take the form:

BiodiversityTarget(b_unit)..  Sum(i$b_unit_i(b_unit, i), Sum(j$bio(j), PotV(i,j)*x(i,j))) + exceed_b(b_unit) >= var_B * B_targets(b_unit)

Where bio(j) is a set of measures that deliver biodiversity value (e.g. WL, FO, LRl, SA, BZ).

Relevant measures

Several existing measures deliver biodiversity co-benefits without needing new parameterization:

Measure Biodiversity relevance
WL Wetland habitat creation — high value
FO Forest habitat creation — high value
LRl Low-lying nature area — high value
BZ10/20 Semi-natural riparian strips
SA Temporary fallow — moderate value
LRh High-land nature area
MW Wetland habitat (small-scale)

Data needed to activate

  • Biodiversity value scores per measure (ha of "equivalent nature area" or biodiversity index)
  • Target definition (minimum area of habitat type? minimum biodiversity index score?)
  • Spatial unit for the target (national? regional? watershed?)

Connection to Tripartite Agreement

The Tripartite Agreement's area floors (LRl, FO, WL, etc.) can be seen as a proxy biodiversity target — they mandate nature-type land uses without explicitly optimizing for biodiversity. When the B module is implemented, the tripartite floors may become redundant or may be replaced by the biodiversity constraint.

Open questions / to document when ready

  1. Which model version has the B module implemented? Can it be ingested?
  2. What biodiversity metric is used (area, species richness, Natura 2000 equivalents)?
  3. Are B targets defined at national, regional, or catchment level?
  4. What is the relationship between var_B and the tripartite floors in the full model?