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ASSESSMENT REPORT
The State of the Wadden Sea and the Implementation of the Esbjerg
Declaration
The 7th Trilateral Governmental
Conference of the Wadden Sea
Leeuwarden, November 30, 1994
Table of Contents:
Part I:
1 Introduction
2 Status of the Wadden Sea Ecosystem
2.1 Introduction
2.2 Pollution
2.3 Disturbance
2.4 Habitat changes and destruction
2.5 Combined effects
2.6 Status of important species
Part II:
3 Status of the Implementation of the Esbjerg Declaration
3.1 Introduction
3.2 Common principles
3.3 Common objectives
4 Conclusions
4.1 Assessment of the ecological state of the Wadden Sea
4.2 Progress in the implementation of the Esbjerg Declaration
ASSESSMENT REPORT
Part I:
Chapter 1 and 2
1 INTRODUCTION
The Trilateral Wadden Sea cooperation
is based on the Joint Declaration on the Protection of the
Wadden Sea, which was signed at the 3rd Trilateral Governmental
Conference on the Protection of the Wadden Sea in Copenhagen
in 1982. In the Declaration, the three countries declared their
intention to consult each other in order to coordinate their
activities and measures for implementing the obligations resulting
from international legal instruments in the field of nature protection,
in particular the Ramsar, the Bonn and Bern Conventions, the
EC Bird Directive and other relevant EC Directives with regard
to the comprehensive protection of the Wadden Sea region as a
whole including its flora and fauna.
The Ministerial Declaration, adopted at the last Trilateral Governmental
Wadden Sea Conference in Esbjerg in 1991 (Esbjerg Declaration),
initiated a new era in the trilateral Wadden Sea cooperation.
The Esbjerg Declaration entails a guiding principle for the trilateral
Wadden Sea cooperation, common principles and common objectives
for the human use of the area based on the common principles.
The adoption of the Esbjerg Declaration resulted in a momentous
input into the protection of the Wadden Sea as an ecological
entity unprecedented in the trilateral cooperation. In the period
since the adoption of the Declaration, the three countries have
been engaged with the implementation of the principles and objectives.
The Assessment Report is an evaluation, prepared for the 7th
Trilateral Governmental Conference on the Protection of the Wadden
Sea, which summarizes
- the progress with respect to the implementation of the Esbjerg
Declaration based on, in particular, the national implementation
reports and
- the status of the Wadden Sea ecosystem based on the Quality
Status Report of the Wadden Sea, where appropriate supplemented
with recent findings.
On the basis of the evaluation in the Assessment Report, the
7th Trilateral Governmental Conference defined the progress and
main common shortcomings with respect to the protection of the
Wadden Sea and determined the main common issues which should
be addressed in the elaboration of the coordinated management
plan.
2. STATUS OF THE WADDEN SEA ECOSYSTEM
2.1 Introduction
In the following, the main conclusions of the 1993 Wadden Sea
Quality Status Report (QSR) are given, where appropriate supplemented
with recent findings.
The anthropogenic impact on the Wadden Sea ecosystem has been
assessed for the impact categories Pollution, Disturbance and
Habitat Changes and Destruction, followed by an evaluation of
their combined effects.
For the assessment, a number of criteria were used which are
listed below:
- the degree of achievement of policy goals for the ecosystem;
- possibilities for regeneration;
- the uncertainty as to effects;
- the risk of an activity;
- the acute or chronic impact;
- the size of the impact.
These criteria have been addressed and specified in the Ministerial
Declaration of the 6th Trilateral Governmental Wadden Sea Conference
(Esbjerg, 1991) by means of a Guiding Principle and a number
of common management principles.
2.2 Pollution
2.2.1 Introduction
The assessment of the pollution status of the Wadden Sea is based
on the evaluation of data on concentrations of substances in
water, sediment and biota. In many cases, data were only available
for a limited period of time. Furthermore, data of different
time periods and/or locations were in many cases not, or only
partly comparable due to differences in monitoring and analysis.
Therefore, conclusions regarding trends in inputs and concentrations,
as well as overviews of geographical differences in concentrations,
should be treated with some caution.
2.2.2 Nutrients
Riverine inputs of phosphorus generally decreased in the
period 1980-1990. Inputs of total nitrogen from the IJsselmeer
did not decrease, whereas Elbe inputs did from 1988-1991. The
latter is, however, most probably a result of the very low flows
in these years. This pattern was confirmed by data from 1991-1993
(compare figure).
Elbe and IJsselmeer inputs (left hand side) and concentrations
(right hand side) of phosphorus (PO43-) and nitrate (NO3-).
(GRAPHICS - under construction)
The pattern of nutrient inputs is reflected in the concentrations
of nutrients in the water column: concentrations of o-phosphate
are slowly decreasing in most parts of the Wadden Sea. Nitrate
concentrations are relatively stable in the western Wadden Sea
and decreasing in the Elbe estuary. As a result, the N/P ratio
increased in the western Wadden Sea and the northeastern Wadden
Sea (Danish part) and decreased in the eastern, Elbe-influenced
Wadden Sea. The biological effects of changing N/P ratios are
still under debate. There are, however, indications that an increase
of toxic algae may occur. Furthermore, changes in algal species
composition may result from the N/P ratio, which deviates substantially
from the natural situation. These changes will probably have
their effects on the whole food chain.
There are strong indications that hyperconcentrations of nutrients
have caused a shift in plankton composition, an increase in primary
and secondary production, and a shift in benthos composition
into the direction of short-lived species. In recent years, an
increase in macroalgae has been observed in the Wadden Sea. This
phenomenon is thought to be caused by eutrophication but further
research is needed. The same can be said for the black spots
on sandy sediment which have increased in size and frequency.
2.2.3 Micropollutants
Contrary to nutrients, micropollutants occur in relatively small
amounts in the marine environment. Two types of micropollutants
can be distinguished, substances of natural origin and man-made
substances or xenobiotics. The heavy metals and many polycyclic
aromatic hydrocarbons (PAHs)belong to the first category. The
second group contains substances like PCBs and pesticides.
The rivers are the main source of inputs of micropollutants into
the Wadden Sea. Little is known about the influx of contaminants
coming from the open North Sea. From the available data on riverine
inputs of heavy metals, no clear trend can be concluded for the
period 1980-1990. However, concentrations of cadmium,
copper and zinc in sediment generally show a decreasing
trend. Despite this decrease, concentrations are still elevated:
in 1990 concentrations of cadmium, zinc and lead in sediment
were 2 to 3 times higher than their background levels. In the
same year, the concentrations of mercury in sediment were up
to 5 times higher than their background level.
The concentrations of the above heavy metals in blue mussels,
show no decreasing trend. Average concentrations of cadmium and
copper are, with the exception of the Elbe estuary, around background
level. Concentrations of mercury and lead are in most cases above
background level
The concentrations of the anti-fouling compound tributyltin (TBT)
in the water of the open western Wadden Sea are below 1 ng/l.
TBT concentrations in dogwhelk, transplanted to harbors and marinas
in the Wadden Sea in 1992, ranged from 0.02 to 0.39 mg kg wet-weight,
and total tin concentrations from 0.07 to 0.69 mg/ kg wet-weight.
Sterility in females may occur already at a total tin concentration
of 0.02 mg/kg wet-weight.
Data on concentrations of the organic micropollutants -PCBs,
PAHs, dioxins- are too limited and patchy to be able to draw
conclusions on trends.
For many other organic micropollutants -a.o. pesticides- there
is hardly any information. A Dutch study has shown that many
of these substances can be identified in the Wadden Sea. Most
of them are not part of the regular monitoring programs.
Only for lindane, more data are available. The concentrations
of this pesticide in water in the eastern Wadden Sea show a decreasing
trend which reflects decreasing inputs from the Elbe as of 1987.
Dutch lindane inputs have remained at the same level in this
period, which is about 50% of the Elbe input figure of 1991.
It is unclear what the effects of the presence of sublethal concentrations
of micropollutants on the ecosystem are. There is increasing
evidence for an impairment of the immune and reproductive systems
in seals and an increased disease frequency in fish. In general,
there is an adverse effect on immune functions, physical development
and reproduction, also in humans. There is not enough known to
conclude whether pollution is the primary cause for diseases
or whether it enhances the development of a disease.
2.2.4 Oil and dangerous substances from shipping and offshore
activities
The oiling rates of dead birds washed ashore have decreased along
the German coast. This was not the case for the Danish and Dutch
Wadden Sea coasts. Most of the oil originates from ships' bunkers.
In the beginning of 1994, an estimated number of 10,000 common
scooters (Melanitta nigra) died in the Schleswig-Holstein
Wadden Sea due to oiling.
It has not been possible to determine effects of the release
of the pesticide Apron-plus in the Wadden Sea ecosystem.
2.3 Disturbance
When comparing the different causes of disturbance, some types
of recreation -including hunting- and commercial fisheries are
regarded as having the biggest disturbance impact on the ecosystem.
Of the various types of disturbance, the negative effects of
interference with the food supply through fisheries have been
quite well documented. The combined visual and acoustical disturbance
caused by slow aircraft -both military and recreational- is considered
the most intensive form of disturbance.
There is, however, a general lack of knowledge about the effects
of other sorts of disturbance and about the effects of disturbance
on the population level.
To fill a part of this gap, the Dutch government has commissioned
a three-year research program (1993-1995) with the aim of developing
a more detailed insight in the interrelationships of water recreation
and nature in coastal waters. This knowledge is necessary to
develop and evaluate policies and management measures for these
waters.
Also in the German Ecosystem Research Project, disturbing effects
of tourism and recreation on natural values are being investigated.
2.4 Habitat changes and destruction
Embankments and coastal protection measures resulted in the
permanent destruction of natural habitats. The salt marsh area
has decreased considerably (see table) and there are hardly any
salt-fresh water transitions left over.
Salt marsh area in 1987 and embanked salt marshes in the past
50 years (source:QSR 1993)
Salt marsh area in 1987 and embanked salt marshes in the past
50 years (source:QSR 1993)
|
region |
salt marsh area 1987 (km2) |
embanked salt marshes in the past 50 years (km2) |
|
The Netherlands |
77 (including summerpolders: 85) |
22 (22%) |
|
Niedersachsen |
85 (including summerpolders: 117) |
20(19%) |
|
Schleswig-Holstein |
51 (including summerpolders: 63) |
107(68%) |
|
Denmark |
81 |
8 (9%) |
|
TOTAL |
294
(including summerpolders:346) |
157 (35%) |
A new threat to the Wadden Sea is the possible sea level rise,
which might result from the green-hous e effect. It is expected
that large areas of tidal flats and salt marshes might disappear.
A subsidence of the bottom caused by the exploitation of gas
may enhance this phenomenon.
Fishery of blue mussels and, in particular, cockles has caused
considerable damage to the Wadden Sea ecosystem, especially the
benthic communities. Many, in some parts all, natural mussel
beds have been destroyed by blue mussel fishery and seed mussel
fishery practices (see table).
There are indications of negative effects of shrimp fisheries
as well.
Present distribution of intertidal mussel beds in the trilateral
Wadden Sea:
|
region |
present area
(km2) |
changes |
number of banks |
source |
|
The Netherlands |
0.2-0.3 |
95% referred to before 1988 |
2 (little parts, little structure) |
Dankers (pers.com.) |
|
Germany-Niedersachsen |
27 |
30 to 50 % |
137 |
Michaelis, 1993 |
|
Germany- Schleswig Holstein |
25 |
stable |
to follow |
Ruth (1994) |
|
Denmark |
8.7 |
105% referred to 1988 |
to follow |
Dahl (1994) |
|
TOTAL |
61.0 |
- |
to follow |
|
The bad recovery of eel-grass from the wasting disease in the
Dutch Wadden Sea is thought to have been caused, amongst others,
by cockle fishery. The distribution of eel-grass in the Wadden
Sea (see table) shows the very low abundance in the Dutch part.
Present distribution of eelgrass in the Wadden Sea (Reise & Buhs
1991, in: QSR 1993):
|
region |
present area (km2) |
% of intertidal |
% of total |
|
The Netherlands |
1.0 |
|
0.1 |
|
0.4 |
|
|
Niedersachsen |
42.8 |
|
6.5 |
|
20.7 |
|
|
Schleswig Holstein |
131.3 |
|
15.1 |
|
63.4 |
|
|
Denmark |
32.0 |
|
8.8 |
|
15.5 |
|
|
TOTAL |
207.1 |
|
4.8 |
|
100 |
|
2.5 Combined effects
It is not possible to give
an indication of synergistic effects of the various human activities
on the ecosystem. It can be assumed, however, that the different
'stress factors' might at least be additive.
Indications of effects of a combination of stress factors come
from research into fish and seal diseases.
An increase in fish disease prevalence was observed in areas
with strong salt-fresh fluctuations (caused by coastal protection
activities). This type of stress, combined with pollution, may
increase the vulnerability for diseases.
The epidemic of the harbor seal in 1988 may have been enhanced
by a decreased resistance due to the state of contamination and
disturbance. The negative effect of contaminants on the seal
immune system was recently demonstrated in a research project.
Decreased immunity caused by stress and pollution makes animals
more vulnerable to a wide range of other threats, amongst which,
human activities.
2.6 Status of some important species
2.6.1 Harbor seal
With regard to the development of the harbor seal population
after the epidemic in 1988, the following conclusions can be
drawn:
- the seal sup-populations in all different parts of the Wadden
Sea have steadily increased since the collapse caused by the
epidemic in 1988;
- the increase in numbers observed for the different sub-populations
is higher after the epidemic than before (12 to 14 %, versus
approx. 9 %);
- the significant differences in pup production between different
sub-areas, which existed before the epidemic, are not observed
anymore;
2.6.2 Waterbirds
According to the recently published report on the evaluation
of numbers and distribution of 41 species of waterbirds, for
the period 1980-1991 (Meltofte et al., 1994), the Wadden Sea
is of outstanding importance to the well-being of a large number
of waterbird populations as a moulting, fattening and wintering
area. The estimated yearly total of individuals adds up to 10
to 12 million. All these species meet the Ramsar criterion, i.e.
more than 1% of their respective populations use the Wadden Sea.
However, in many cases more than 50%, and in some cases even
the whole population, occur in the Wadden Sea.
For breeding birds and quite a number of staging waterbird populations,
the islands and salt marshes, together with the adjacent polders
and nearby parts of the North Sea, make up an integrated part
of the Wadden Sea ecosystem.
During recent decades, considerable increases of total flyway
population sizes have occurred for cormorant (Phalacrocorax
carbo), dark-bellied brent goose (Branta bernicla),
barnacle goose (Branta leucopsis), eider (Somateria
mollissima), oystercatcher (Haematopus ostralegus)
and avocet (Recurvirosta avosetta). The increases are
attributed to improved protection -more sanctuaries, reduced
hunting pressure- and possibly improved feeding conditions due
to eutrophication.
Islandica knots, wintering in northwestern Europe, have
decreased considerably.
The breeding populations of kentish plover (Charadrius alexandrinus)
and little tern (Sterna albifrons) have decreased all over the
Wadden Sea due to disturbance from visitors on the beaches, where
these birds breed. Considerable increases in the Wadden Sea breeding
populations, over most of this century, are known for eider (Somateria
mollissima), oystercatcher (Haematopus ostralegus),
black-headed gull (Larus ridibundus), common gull (Larus
canus), lesser black-backed gull (Larus fuscus) and
herring gull (Larus argentatus) . These changes may be
attributed to the already above mentioned improved protection
and food situation.
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