measuring the vulnerability of a community of species to a given pressure: benthos and bottom trawl...
TRANSCRIPT
Measuring the vulnerability of a community of species to a given pressure:
Benthos and bottom trawl in the Barents Sea.
Jørgensen, LL, Certain G, Thangstad T, Planque B
Spatial workshop outputs: Annual meeting Paris 3-7 Dec 2012
How environmental disturbance affects a community of species
Benthic community delivering ecosystem goods and services
Benthic end member community with opportunistic species
Mixture where S, A and B increase
Disturbance
Pearson & Rosenberg 1978
Classical, experimental approach to measure disturbance effect on biodiversity:
Benthic community
Environmental noise Directed disturbance (”Pressure a, b or c”)
Natural fluctuations difficult to separate from pressure induced
Need to make the link between pattern and pressure more explicit
Pointing toward the species showing the ”effect”
qS
i
qi
q pD
1/1
1
qS
i
qiiz
q ZpD
11
1
1
Hill Leinster & Cobbold (2012)
Zi = the ”average” similarity of species i with
the remaining species
All species differs in the same way
Coding species in accordance to the effect from a defined pressure
Sp
ecie
s
Traitssize growth
Sp. 1
Sp. 2
Sp. 3
3 1 11 3 3
3 2 1
mobility
Theoretical indicator species:3 3 3
4
2
3
A similarity measure is convenient if the theoretical species has some meaning ex:
”the most vulnerable species”
0
Trawling impact 2
93 B
aren
ts S
ea S
pec
ies
6 TraitsMobility Speed Strata Body shape Body Texture Mean weight
A theoretically super-vulnerable species
From an given community sample, we can measure the
community vulnerability
V = community vulnerabilityv= species vulnerabilityP = frequencyi=1...S speciesj=1...L locations
S
i i
ijj v
pV
1 1
Application to Benthic communities in the Barents Sea (1)
Trawled area (VMS)
Benthos station
Norwegian coast Bear Island Hopen deep Front Svalbard
Co
mm
un
ity
Vu
lner
abili
ty
2
4
6
Application to Benthic communities in the Barents Sea (2)
T nT T nT T nT T nT T nT
Statistical distribution of community vulnerability in Hopen Deep area:
Expected vulnerability
Fre
qu
ency
Benthos communities in trawled area
Benthos communities in untrawled area
HighLow
Conclusion
This general method estimate the community vulnerability if a species vulnerability to a given
pressure can be assessed.
•The geographical borders of the used polygons needs more evaluation
•Other covariates potentially affecting a community vulnerability ?
•New more exhaustive datasets will be included
Way forward