BSEP116B Biodiversity in the Baltic Sea - Helcom

Figure 7.8.a. MARXAN ’best portfolio‘. This set of selected areas provides the best fit to the targets chosen for the
network. b. MARXAN selection frequency. The deeper red colours indicate areas that were selected more often than others
(more yellow), indicating the importance of selecting them for inclusion in the MPA network. Technical details: The figures
reflect targets set to represent a minimum of 20% of all benthic marine landscapes and IBAs, 60% of all grey seal haul-out
sites and 100% of all cold-water coral occurrences (60% of the dead structures). The portfolio adds complementary sites
to Natura 2000 SACs, using BLM=2.5 (Boundary Length Modifier that determines the level of clustering of planning units
into conservation areas to improve spatial cohesion of the portfolio), stratified targets and a measure of suitability. The
selection was conducted using simulated annealing with iterative improvement using 2 million iterations in 100 runs and a
‘penalty value’ of 1.1 for all features. All targets were met. From: Liman et al. (2008).
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factors 14 and the suitability of sites were also taken
into account, meaning that the conservation targets
should be met with a minimum impact on other
interests and that the relative suitability of potential
conservation sites should be considered. The size of
the sites selected should also reflect the broad-scale
objective of the exercise, meaning that relatively
large sites should be selected for protection of the
ecosystem on a regional scale.
Results
The scenario presented here was developed with
the aim of demonstrating a systematic approach
to selecting sites that represent the broad-scale
variation in the Baltic Sea. It should therefore be
emphasized that the results presented below are
only examples of what a representative MPA
14
Socio-economic factors in the analysis were oil terminals,
harbours, potential ship accident areas, major shipping
lanes, recommended shipping routes and human population
density.
network in the Baltic Sea could look like given
the specific criteria applied in this assessment.
The results presented in Figure 7.8 relate to the
scenario representing a minimum of 20% of all
benthic marine landscapes. To view results of the
other scenarios, namely, the 10% and 30% scenarios,
see Liman et al. (2008).
Figure 7.8a shows the one set of sites (selected
during repeated MARXAN runs) that meets all the
above-mentioned conservation targets and principles
in the most efficient manner. According to this
particular analysis, the area of the additional sites
needed, as a complement to the existing sites, to
fulfil the recommended 20% representation target
corresponds to approximately three times the
area of the existing SACs 15 . The selected network
of sites in Figure 7.8a, with its combination of
selected and already existing sites, covers an area
15
It must be kept in mind that marine features protected
under the Habitats Directive do not include most of the
benthic marine landscapes.