Calculating biologically accurate mitigation credits: Insights from the California tiger salamander

Christopher Searcy, H. Bradley Shaffer

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

Current conservation mitigation plans often fail to ensure full in-kind habitat replacement for endangered species, which suggests the need for improved methods for calculating mitigation credits. A simple, yet biologically meaningful method for calculating mitigation credits would be to let the number of mitigation credits assigned to a parcel of land scale with the reproductive value of the individuals occupying that parcel. This can be accomplished by dividing the population into 2 or more subdivisions with different reproductive values, calculating the densities of these subdivisions as a function of one or more habitat parameters, and then forming a weighted sum of these densities such that each density distribution is weighted by the reproductive value of its respective subdivision of the population. This weighted sum is the density distribution of reproductive value, and by integrating it over a particular parcel, one can determine the mitigation value of that parcel. We carried out this procedure for a population of California tiger salamanders (Ambystoma californiense), with distance from breeding site as our habitat parameter and the 3 visually identifiable age classes (adults, juveniles, and metamorphs) as our population subdivisions. This led to a density distribution of reproductive value that decreased exponentially with increasing distance from a breeding site. Mitigation strategies derived from this function will be more likely to ensure the persistence of California tiger salamander populations than current approaches, which assign all land within 1.6 km of a breeding site the same mitigation value. Use of the density distribution of reproductive value as a basis for mitigation plans is a procedure that can be applied to all endangered species, and it should improve the quality of mitigation decisions.

Original languageEnglish (US)
Pages (from-to)997-1005
Number of pages9
JournalConservation Biology
Volume22
Issue number4
DOIs
StatePublished - Aug 1 2008
Externally publishedYes

Fingerprint

credit
mitigation
breeding sites
founder effect
breeding site
endangered species
Conservation
habitats
habitat
age structure
Ambystoma californiense
salamander
age class
persistence
replacement
methodology
distribution

Keywords

  • Ambystoma californiense
  • California tiger salamander
  • Density distribution
  • Mitigation credit
  • Pond-breeding amphibian
  • Reproductive value
  • Survivorship value

ASJC Scopus subject areas

  • Environmental Science(all)
  • Ecology
  • Environmental Chemistry
  • Nature and Landscape Conservation

Cite this

Calculating biologically accurate mitigation credits : Insights from the California tiger salamander. / Searcy, Christopher; Shaffer, H. Bradley.

In: Conservation Biology, Vol. 22, No. 4, 01.08.2008, p. 997-1005.

Research output: Contribution to journalArticle

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