LCA Food 2012 in Saint Malo, France! - Manifestations et colloques ...

PLENARY SESSION 3: METHODS FOR BIODIVERSITY AND SOIL QUALITY 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
2. Methods
We calculated land use impacts on biodiversity according the UNEP/SETAC Life Cycle Initiative
Framework (Koellner et al., 2012a; Milà i Canals et al., 2007), and distinguished between occupation (land
use), transformation (land use change) and permanent impacts (irreversible changes in ecosystems, see Fig
1). Occupation and transformation impacts were calculated based on regional extinction risk of non-endemic
species. Permanent impacts were based on the extinction risk of species endemic to that ecoregion. Below,
we outline how the number of potentially extinct species was estimated and how we derived regional characterisation
factors for the three land use impacts (occupation, transformation, and permanent impacts).
Figure 1. Graphical illustration of occupation, transformation and permanent impacts (adapted from Koellner
et al., 2012a)
2.1 Calculating potential regional mammal species extinctions due to land transformation and occupation
As in earlier land use LCIA studies, we based our assessment on changes in the predicted species numbers
according to the species-area relationship (SAR), a model often used to predict extinction rates due to
habitat loss. The SAR is derived from island biogeography theory, which describes a non-linear (often
power) function between species richness S and area A of island ecosystems (Rosenzweig 1995):
S= cA Eq. 1
with two constants c (species richness of area A=1) and z (species accumulation rate). If the area of primary
habitat is reduced from an original area to an area , and if we assume , then the
relative number of species S remaining can be calculated as (Koh and Ghazoul 2010):
z
A A c org new new = corg z
Snew Sorg =
Eq. 2
The number of species lost in an ecosystem due to habitat loss is given as (Koh and Ghazoul 2010):
A æ ö
new
ç
è A
÷
org ø
æ A ö
new
Slost = Sorg - Sorg ç
A
÷
è org ø
Eq. 3
As SAR models tend to overestimate extinction rates, we base our method on an adapted SAR model, the
matrix-SAR developed by Koh and Ghazoul (2010), which gave more realistic estimates of species extinction
rates than the conventional SAR model. Unlike the conventional SAR, the matrix-SAR model considers
that the human-modified area (i.e. the land use matrix) is not void of species, but provides a certain habitat
quality for different species groups. This is accounted for by adapting z, the exponent of Eq. 3, depending on
the composition of the matrix (i.e. the area share of different land use types pi) and the sensitivity of each
taxonomic group to different land use types i (Koh and Ghazoul 2010):
å
n
z
S lost
z ¢ = z* pis i ; with Eq. 4
i
A i
pi =
Aorg - Anew s i
Eq. 5
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