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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.

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Presentation on theme: "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."— Presentation transcript:

1 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

2 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

3 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

4 Pointing toward the species showing the effect HillLeinster & Cobbold (2012) Zi = the average similarity of species i with the remaining species All species differs in the same way

5 Coding species in accordance to the effect from a defined pressure Species Traits sizegrowth Sp. 1 Sp. 2 Sp mobility Theoretical indicator species: A similarity measure is convenient if the theoretical species has some meaning ex: the most vulnerable species 0

6 Trawling impact 293 Barents Sea Species 6 Traits MobilitySpeedStrataBody shapeBody TextureMean weight A theoretically super-vulnerable species

7 From an given community sample, we can measure the community vulnerability V = community vulnerability v= species vulnerability P = frequency i=1...S species j=1...L locations

8 Application to Benthic communities in the Barents Sea (1) Trawled area (VMS) Benthos station

9 Norwegian coast Bear Island Hopen deepFrontSvalbard Community Vulnerability Application to Benthic communities in the Barents Sea (2) T nT

10 Statistical distribution of community vulnerability in Hopen Deep area: Expected vulnerability Frequency Benthos communities in trawled area Benthos communities in untrawled area HighLow

11 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


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