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Dieren en planten

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Nature policy   Ecosystem goals North Sea   Nature value map North Sea   

Ecosystem goals for the North Sea

In order to protect nature at sea, you must know where the valuable nature is located, what the present quality of the nature is and what kind of quality is desired. Partly on behalf of the results of the nature policy and the spatial planning of the North Sea (see the Fifth Note Environmental Planning), this kind of knowledge has been brought together in the project 'Ecosystem goals for the North Sea'. One effect of these goals has led to the nature value chart for the Dutch section of the North Sea.

  • Goal 1: Maintain natural dynamic processes

    Sea currents and the resulting transportation of sand and mud at sea will only be disrupted by large-scale sand exploitation in deep pits. This is not taking place momentarily, however there are plans in this direction (exploiting concrete sand in the North Sea). Current patterns along the coast (the 'coastal river') can be disturbed due to the construction of the Second Maas Plain, maintenance of piers and channels, coastal defence works and, in a limited manner, from fisheries.
    The suggested scales for these goals are summerized in the underlying table.

    parameter present value target value
    larvae flow to coast and Wadden Sea unobstructed unobstructed
    mud transportation to the Wadden Sea (106 tons/year) 20 20
    Source: Parameters Ecosysteemdoelen Noordzee, Expertisecentrum LNV 2002
  • Goal 3: Enlarge the estuarine character (particularly for delta regions)

    The quality of the ecosystem in the delta waters is particularly under pressure due to continuing high concentrations of contaminated materials in the Schelde water. The concentrations of nutrients is also too high, which can lead to blossoms of toxic or plague algae. Furthermore, cockle fisheries forms a threat for the bird populations and the shellfish farming brings risks of introducing system-foreign species into the delta waters (as happened with the Pacific oyster in past decades). The construction of the Second Maasvlakte means a major intervention on the existing intertidal region.
    In the large tidal waters of the Delta, the tide has been tremendously tempered by the Delta Works. Increase in the difference between high and low tide (the fall) could lead to a large increase in the areal of exposed banks.
    The proposed indicators for reaching this goal are summarized in the table below:

    parameter present value target value
    Exposed banks (in ha) 20,000 40,000
    Fall (m) decrease increase
    boundaries fresh/brackish/saline disturbed historical positions
    Source: Parameters Ecosysteemdoelen Noordzee, Expertisecentrum LNV 2002
  • Goal 5: At most, take incidental action against algae blooms; preserve and where necessary restore natural diversity among the plankton

    Reaching this goal is hindered in particular by the continuing high supply of nutrients to seawater. The blossoming of non-toxic organisms, such as phaeocystis and Noctiluca scintillans can cause disorder in the ecosystem locally. Blossoming of toxic algae, such as dinophysis brings dangers for all plankton consumers, but especially for man (via shellfish). New toxic algae can end up in the North Sea ecosystem via ballast water from ships. Furthermore, one expects so much turbidity from large-scale sand exploitation that it will influence the plankton.
    The proposed indicators for reaching this goal are summarized in the table below:

    parameter present value target value
    Nurtrients (coast) in the winter
    . level N and P (-mol/l)
    . proportion N and P
    . emission N and P (ton/year)
    N 60-90; P 1.4-3.0
    23
    N 400; P24
    N 14-24; P 0.6-0.7
    16
    0
    Chlorophyll a (mg/m3) 15-20 7
    presence plague algae (cells/liter)
    . Karenia mikimotoi
    . Alexandrium spp.
    . Dinophysis spp.
    . Pseudonitzschia spp.

    1110,00010,000,000

    111001000
    presence Pheaocystis (number days > 106 cells/liter) 40 10
    oxygen level (mg O2/l) 5 6
    ballast water (%treated) 0 100
    Source: Parameters Ecosysteemdoelen Noordzee, Expertisecentrum LNV 2002
  • Goal 6: Maintain and where necessary restore the diversity of the bottom fauna, including populations of long-living and slowly reproductive species

    The benthic fauna in the North Sea suffers in particular from beam trawl fisheries with tickler chains. Long-living animal species, such as the quahog and the red whelk, are declining rapidly in areas where intensive flatfish fisheries take place. Other shellfish, echinoderms, crabs, lobsters and benthic fish are also disappearing to make room for a fauna consisting mostly of worms. In addition, the benthic fauna is also influenced by pollution. Eutrophication in particular can lead to disturbances or a different composition of the fauna.
    The construction of the Second Maasvlakte means the disappearance of a large surface area of biotopes in a shallow coastal zone.
    Oil and gas exploitation platforms have a positive effect on the benthic fauna indirectly. There is a safety zone of a radius of 500 meters around every installation, in which shipping, fisheries and activities such as sand extraction is not allowed. In these zones, the benthic fauna is not disturbed as much than elsewhere at sea. Locally, the discharge of drilling mud can lead to disturbance.
    (Future) wind parks and possible placement of transmitting installations will also be surrounded by a safety zone which is favorable for benthic fauna.
    The proposed indicators for reaching this goal are summarized in the table below:

    parameter present value target value
    population size quahog in the northern NCP (number animals/m2) 10-50 50
    population size whelk in the northern NCP (number animals/m2) 0,01 0.05-1.5
    imposex whelk (open sea) and dog whelk (coast) (% of females) 25-100 <10
    Diversity index (Shannon-Wiener) region-dependent 1.1-3.0 increase
    Areal without bottom agitation (percentage NCP less than 1x per 10 years fished) 9 15
    Oysterbanks (ha) 0 15
    Source: Parameters Ecosysteemdoelen Noordzee, Expertisecentrum LNV 2002
  • Goal 7: Promote diversity of the fish fauna

    The safety zone around offshore platforms and wind energy parks is also a refuge for benthic fish. Pollution from the offshore and shipping can form a threat. Gravel excavation is damaging for species that lay their eggs on gravel substrates (such as herring)
    The fisheries has a major influence on the fish populations. The target species threaten to be overfished and unintended by-catch species, such as sharks and rays, have declined strongly in number. Sharks and rays are also sensitive to electromagnetic fields which are generated by electricity and telephone cables.
    The construction of the Second Maasvlakte will probably have a significant effect on the migration of fish larvae to the nursery in the Wadden Sea, due to repositioning the coastal river.
    The proposed indicators for reaching this goal are summarized in the table below:

    parameter present value target value
    average size of the fish community (%>25 centimeters) 28 40
    presence of long-living species (number/km2)
    . thornback ray
    . greater weever

    0.1-0.3
    0

    6
    50
    spawning biomass commercial species above the precautionary level (million kilograms)
    . herring
    . cod
    . plaice
    . lesser sandeel
    . sole
    . whiting


    772
    54
    289
    706
    40
    257


    1300
    150
    300
    600
    35
    315
    discards (% weight of catch)
    . fish
    . benthic animals

    27
    46

    minimalize
    minimalize
    Diversity (numbers and species) unknown increase
    Source: Parameters Ecosysteemdoelen Noordzee, Expertisecentrum LNV 2002
  • Goal 8: Preserve and where necessary restore the living conditions for sea and coastal birds

    Lighted drilling platforms can have negative effects on migrating birds. Birds can also be victims of gas flames during burn off of gas which is released during trial drills. Even more serious is the risks of discharges from mineral and vegetable oil from shipping.
    The fisheries have positive as well as negative influence on birds. A number of sea and coastal birds become entangled in standing rigging. The shellfish fisheries in tidal and coastal regions perform an attack on the supply of staple food, such as cockles and spisula. Positive is the effect of by-catch which is thrown overboard. Gulls and petrels in particular profit.
    The influence of pollution on birds is thought to be less serious. Effects of materials such as PCBs on the immune system of the birds has not been sufficiently studied.
    Wind parks and future transmission installations bring birds the risk of collisions. Military activities disturb resting and foraging birds.
    Recreation on the beach and in coastal waters can disturb foraging birds and result in the disappearance of nesting places. The construction of the Second Maasvlakte could mean the loss of a large foraging area.
    The proposed indicators for reaching this goal are summarized in the table below:

    parameters present value target value
    nesting pairs little terns (number) Wadden Sea 150
    Delta 350    		 Wadden Sea 200
    Delta 500
    nesting pairs Kentish plover (number) Wadden Sea 60-80
    Delta 200    		 Wadden Sea 150
    Delta 300
    common scoter (number) 100,000 same
    guillemot and auk (number) NCP 200.000
    Bruine bank >1/km2    		 same
    areal nesting area little tern and Kentish plover (ha) 2000 4000
    presence staple food and small fish
    . lesser sandeel
    . herring
    . sprat
    . shellfish

    1145
    825
    unknown
    10-225

    1300
    600
    depending upon year advice
    to be determined
    oil victims (% dead birds covered in oil on the beach)
    . guillemot (open sea)
    . common scoter (coast)


    70-80
    70-80


    0
    0
    Source: Parameters Ecosysteemdoelen Noordzee, Expertisecentrum LNV 2002
  • Goal 9: Preserve and where necessary restore the living conditions for populations of marine mammals

    Because they are at the top of the food chain, marine mammals have relatively the most hinder from pollution in sea, whether it comes from offshore, shipping or from land. Reproduction and health problems can result.
    Standing rigging causes problems for marine mammals. Porpoises can drown in the nets of cod fishermen, seals can drown in the fykes lacking retaining nets.
    Finally, disturbance of resting seals is a problem. This can be caused by recreationists (on the beach or in tidal regions), from shipping or from military activities.
    The proposed indicators for reaching this goal are summarized in the table below:

    parameter present value target value
    harbour seal (number) Wadden Sea 5000
    Voordelta 130    		 Wadden Sea >6500
    Voordelta 300
    porpoise (number) NCP 20,000
    Voordelta 30    		 NCP 50,000
    Voordelta > 250
    areal rest and nursing area for seals (ha)
    . Wadden
    . Delta

    maintain
    20,000


    40,000
    presence staple food and small fish
    . lesser sandeel
    . herring
    . sprat

    1145
    825
    unknown

    1300
    600
    depending upon year advice
    by-catch marine mammals (% of the population) 2.7 (North Sea) <1.7
    Source: Parameters Ecosysteemdoelen Noordzee, Expertisecentrum LNV 2002
  • Goal 10: Maintain the possibilities for experiencing the dynamics of the forces of nature, wind, water, sand and salt at the transitions from open water to dry coastal zones.

    One has not been able to establish any clear effects of human activity as far as this goal is concerned.

  • Goal 11: Maintain the openness, splendour, quietness and obscurity; this holds true for the whole coastline in the north-south direction and perpendicular to the beach up to the line of visibilty ('clean horizon').

    Static constructions such as drilling platforms and windmill parks disrupt the open horizon. On the other hand, ships at sea enlarge the feeling of an openness. Military practices and noisy forms of aquatic recreation disturb the stillness.
    The proposed scale for this goal has been summerized in the underlying table.

    parameter present value target value
    unhinderd view unknown maintain present situation
    Source: Parameters Ecosysteemdoelen Noordzee, Expertisecentrum LNV 2002
  • Goal 12: Maintain and where necessary promote opportunities for being in the presence of various fauna, such as birds and fish

    Pollution plays a prominent role in this goal. Oil victims and marine litter substantially reduce the value of experiencing nature along the coast. In addition, disturbance due to recreation and military activities also play a role.