MOF, Alm.del - 2017-18 - Bilag 35: Rapporten fra det internationale ekspertpanel om evaluering af de danske marine modeller

Miljø- og Fødevareudvalget 2017-18
MOF Alm.del Bilag 35
Offentligt

Executive summary

- International evaluation of the Danish marine models

To be published after the heari ng of the evaluati on report

10. oktober 2017

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MOF, Alm.del - 2017-18 - Bilag 35: Rapporten fra det internationale ekspertpanel om evaluering af de danske marine modeller

Table of contents

Introduction .......................................................................................................... 1

Overall assessment and conclusions ................................................................... 4

Recommendations for going further ..................................................................... 5

MOF, Alm.del - 2017-18 - Bilag 35: Rapporten fra det internationale ekspertpanel om evaluering af de danske marine modeller

Introduction

This report presents a scientific review of the Danish management approach regarding

coastal waters in relation to the implementation of the European Water Framework

Directive (WFD) in Denmark. The parties to the Agreement on Food and Agriculture

Package (22 December 2015) have decided to evaluate the modelling tools (pressure-

impact models) used to calculate the mitigation demands for nitrogen (N) runoff from

land in the Danish River Basin Management Plans. The results of the evaluation will be

utilised towards the development and application of models in the 3

generation water

plans valid for 2021-2027.

Task description by t he M inistry of Food and Agriculture

The task of the evaluation panel is to perform a thorough evaluation of the marine

modelling tools that form the basis for the mitigation demands for land-based nitrogen

(N) runoff in the Danish River Basin Management Plans with regards to the importance

of N as well as other relevant pressures such as phosphorous, fisheries etc. In particular,

the evaluation panel has to:

Evaluate the use of models for determination of type-specific reference values

(according to the Water Framework Directive, Annex 2) for the water quality

element phytoplankton (chlorophyll).

Evaluate the use of models to determine environmental targets (Maximum

Allowable Inputs (MAI) of nitrogen)) and mitigation needs to achieve good

environmental status and evaluate differences and similarities between the use

of different methods and model types for coastal waters with different typology.

Evaluate the estimated nitrogen target loads and mitigation needs in the Danish

River Basin Management Plans and evaluate the method for determining the

Danish proportion of total mitigation needs. How is the current environmental

status in Danish coastal waters determined by N runoff from Danish land areas

in relation to other pressures such as N released from sediments and N loads

from catchments in neighbouring countries and airborne N deposition (the

Danish share of the total mitigation needs related N)?

ii.

iii.

Further, the Panel is expected to address the technical questions and comments from

the stakeholders.

Recruitment of experts

The Danish Ministry of Environment and Food has been responsible for the recruitment

of an international panel of five experts to carry out the evaluation. The recruitment of

experts has been conducted by a nomination process where the Danish Ministry of

Environment and Food has requested water management authorities in other countries

(Sweden, Finland, Poland, Germany, The Netherlands and England) and the European

Environment Agency, Joint Research Centre (JRC) and the European Commission (DG

Environment) to nominate experts to conduct the evaluation. It has been stated in the

request that the nominees should have expert knowledge in the following areas: marine

ecology, marine ecosystem models, statistical methods and experience in marine water

management in relation to the Water Framework Directive.

The request by the Ministry resulted in the nomination of 14 experts of which 9 experts

subsequently indicated that they were interested in being part of an expert panel. Of

these, the Ministry has selected the following five experts to conduct the evaluation:

MOF, Alm.del - 2017-18 - Bilag 35: Rapporten fra det internationale ekspertpanel om evaluering af de danske marine modeller

•

Professor Peter Herman, Deltares, Institute for applied research in the field of

water and subsurface, the Netherlands.

Professor Alice Newton, NILU – Norwegian Institute for Air Research

Professor Gerald Schernewski, Leibniz Institute for Baltic Sea Research,

Warnemunde

Director Bo Gustafsson, Baltic Nest Institute (BNI), Stockholm University,

Sweden

Senior Researcher Olli Malve, Finnish Environment Institute SYKE

Professor Peter Herman was chosen as chairman of the Panel

•

The five experts were chosen according to an assessment of their qualifications with

regards to experience with and competences in the following fields of study:

marine

ecology/coastal ecology,

coastal

ecosystem modelling, use of statistics in environmental

science

and

marine management experience related to the implementation of the Water

Framework Directive.

Ai m and f ocus of the evaluati on

This section presents the aim and focus of the evaluation according to the international

panel (hereafter referred to as the Panel) and should therefore be seen as the Panel’s

further operationalisation of the task description.

The evaluation will answer questions related to points (i)-(iii) in the task description

above and is therefore focused on the scientific underpinning of the plans, in particular

the modelling tools. The evaluation must take into account the internationally agreed

goals of achieving Good Ecological Status in the Water Framework Directive.

The main aim of the evaluation

The main aim of the evaluation is to review whether the marine models – as

presented in the Scientific Documentation Report and as commented by the

researches and stakeholders –

provide solid and robust scientific evidence that the

proposed reductions in land-based N runoff will be both necessary and sufficient to

reach Good Ecological Status as defined in the Water Framework Directive.

•

By “solid”, the Panel means well based in international scientific literature, well

performed, credible

By “robust”, the Panel means not unduly dependent on arbitrary details, reliable

with acceptable precision

By “necessary”, the Panel means that by doing less the goals would not be

reached

By “sufficient”, the Panel means that by executing the plans, there is a high

probability of reaching the goals

•

The scope of the evaluation does not include other models than the marine model and

other environmental targets than those applying to coastal areas. The scope of the

evaluation does not include the societal costs and benefits of the measures that would

be needed to fulfil the environmental targets.

MOF, Alm.del - 2017-18 - Bilag 35: Rapporten fra det internationale ekspertpanel om evaluering af de danske marine modeller

The basis for the ev al uation

The basis on which the Panel has made the final evaluation consists of the following

materials:

•

The Scientific Documentation Report written by Aarhus University (DCE) and

DHI in June 2017, which documents the model tools and calculated MAI that

were developed for the Ministry over the period 2013-2015.

Questions and comments from the stakeholders to the Scientific Documentation

Report (see Annex 1 of the evaluation report)

Answers from the researchers to questions and comments which were

formulated by the Panel after the members of the Panel read and considered

the report as well as the questions and comments from the stakeholders (see

Annex 2a and 2b of the evaluation report).

Answers from the Panel on how they took into account each of the technical

questions and comments from the stakeholders (see Annex 3 of the evaluation

report).

Selected background materials cited by the researchers, the stakeholders and

the Panel

•

The eval uation pr ocess

It is considered crucial that the evaluation of the Danish marine models be performed by

independent scientists. In order to guarantee independence, it was decided that the

Ministry of Environment and Food, the scientists from AU and DHI and the stakeholders

should keep arm’s length to the Panel throughout the process of the evaluation.

Implement Consulting Group (Implement) was engaged by the Ministry to facilitate the

process.

The evaluation process started in June 2017. It resulted in an evaluation report on 19

September, which was finalised after a writing workshop in Helsingør which took place

between 11-15 September. After the hearing process between 19. September and 2

October some minor corrections were made to the final report which was completed on

10 October.

The heari ng proc ess

A hearing of the evaluation report among stakeholders from Blåt Fremdriftsforum and the

scientists from AU and DHI took place between 19 September and 2 October. Three

stakeholder organisations plus AU and DHI submitted additional comments and

questions which were answered by the Panel between 2 and 9 October. The additional

comments, questions, and answers are listed in the document

Høringsbilag

which was

completed 10 October.

When studying the reactions of researchers and stakeholders, the Panel realized that a

few factual errors occurred in its report, and that furthermore the choice of wording was

not always entirely precise and consistent, with respect to the difference between water

body specific, type-specific, and regionalized references, targets and MAIs. In order to

avoid further confusion with other readers of the report, the Panel decided to slightly edit

the report and the final version was therefore submitted on 10. October. The changes in

the final version, compared to the version commented upon by the stakeholders and

researchers, have been summarized in the first Table in the document

Høringsbilag.

MOF, Alm.del - 2017-18 - Bilag 35: Rapporten fra det internationale ekspertpanel om evaluering af de danske marine modeller

The Panel hopes that the attention given to the views of the stakeholders and the

responses of the researchers during the scientific scrutiny of the Scientific

Documentation Report will help to build trust between the parties and contribute to a

successful outcome.

2. Overall assessment and conclusions

The Water Framework Directive aims at restoring Good Ecological Status in surface

waters in Europe. The Scientific Documentation Report proposes measures of nutrient

load reduction to reach this Good Ecological Status in Danish transitional and coastal

waters. The Panel fully endorses the importance attached to nutrient reductions as a

necessary requirement to reach this Good Ecological Status and stresses the

importance of nutrient conditions as a modulating factor interacting with any additional

measures taken to improve the state of the system.

In comparison with many other European countries, Denmark has excellent databases,

models and scientific expertise as a basis for the implementation of the Water

Framework Directive. The Panel was delighted to see that these resources have been

mobilised to achieve a leading position at the European scale. The Panel was impressed

by the openness and transparency of the interaction between government, researchers

and stakeholders as well as by the high intellectual level of the discussions. This open

exchange of ideas and opinions is a perfect basis for a further improvement of the

scientific basis for the WFD implementation.

The Panel has reviewed the choice of indicators and procedures, in the context of the

WFD requirements and specifications, and found that the indicators, the methods to

determine reference conditions and the methods to determine required actions were

WFD compliant. The Danish implementation is based on either direct historical

observation or model determination of reference conditions. Little or no uncontrollable

“expert judgement” is involved. In that respect, the Danish models are attaining the

highest possible standard of WFD implementation.

The Panel has analysed the consequences of using a relatively coarse typology of

coastal waters for calculating reference conditions, targets and Maximum Allowable

Inputs of nitrogen. The Panel concludes that the use of a coarse typology has led to

reduction requirements that are not optimal for each of the individual water bodies. The

Panel is convinced that the full use of available data and models would allow Denmark to

forego the typology and develop advanced, specific reduction targets for each water

body. The Panel recommends focusing on the water body scale of resolution throughout

the scientific process. The regional grouping of reduction measures should be decided

upon only at the stage of translating scientific advice into management action plans.

The Panel has analysed the indicators used and concluded that Chlorophyll a is a useful

intercalibrated indicator of phytoplankton, while Kd is less optimal as an indicator of

benthic angiosperms and macrophytes. The other indicators, used in the statistical

modelling only, currently present methodological problems and are not yet mature

enough for inclusion in the management plans. The Panel has identified promising

developments in the modelling with respect to angiosperm and macrophyte indicators

and made recommendations on how to extend and develop the indicator set in the

future.

In view of the large efforts in the past to remove P load from point sources, the Panel

endorses the emphasis placed in the Scientific Documentation Report on reducing N

loads from diffuse sources. However, at least in principle, there could be an additional

role for P load reduction and for seasonal regulation of the N load. The Panel is of the

MOF, Alm.del - 2017-18 - Bilag 35: Rapporten fra det internationale ekspertpanel om evaluering af de danske marine modeller

opinion that these options merit further scientific exploration, especially in watersheds

where high efforts for N load reduction are required.

Although the maintenance of two parallel modelling lines (statistical and mechanistic)

may seem redundant at first sight, the Panel strongly endorses maintaining these lines.

Given the wealth of data available, it provides unique possibilities for evidence-based

checking of mechanistic model results. The Panel assesses the mechanistic model as a

state-of-the-art, very comprehensive tool, but emphasises that independent checking on

data as well as uncertainty analysis remain necessary and can be performed by the

statistical approach. This coherence can be optimised by improving the approach and

methods of the statistical modelling.

The Panel endorses the general logic of the methodology to derive reference and target

values from the models and to calculate the required N load reduction to reach the

targets. The Panel has identified several points in the workflow where averaging is

performed. This results in interdependence of model types, loss of indicator resolution

and loss of spatial resolution. It also adds complexity to the procedure and makes it very

difficult to understand. None of these losses are necessary since the model results and

database do permit a fully transparent derivation of water body-specific required nutrient

reduction.

Summing up these different aspects of the work, the Panel positively evaluates that

nutrient load reductions are based on

solid

scientific evidence and generally high-level

modelling approaches. The Panel is very positive about the near lack of expert judgment

in the work and is of the opinion that in the few places where it does occur, it is not

necessary and can be removed. The general (country-averaged) level of required

nutrient load reduction compares favourably with independent efforts in similar areas and

seems a

robust

measure of what is needed. At the same time, the Panel assesses the

spatial resolution of the required efforts as

unnecessarily coarse.

The Panel is

convinced that the rich database, combined with an

improved statistical approach

and

the high-resolution mechanistic modelling tools, are able to derive improved, water body-

specific MAI values. Current scientific insight endorses the view that the overall

reductions proposed are

necessary,

but cannot guarantee that they will be

sufficient.

Especially for benthic angiosperms and macrophytes, additional measures may be

needed.

3. Recommendations for going further

Monitoring:

The Danish national monitoring programme used in the Scientific

Documentation Report includes more than 90 stations along the coast and in the sea. It

is very comprehensive and is generally well adjusted to the WFD requirements. It forms

the basis for the further development of models, for most calculations and is required to

evaluate the success of measures and whether the targets of the WFD are met. The

Panel recommends maintaining this monitoring system at full strength and assessing if

additional monitoring stations will be required for a water body-specific management.

Typology:

The typology has weaknesses in reflecting the individual properties of fjordic

water bodies. Instead of suggesting a refinement of the existing typology, we

recommend calculating reference conditions and targets for each of the 119 water

bodies in Denmark. Denmark is one of the few countries in Europe, where the necessary

data, expertise and models are available for such a comprehensive approach. By taking

specific conditions and individuality of every water body into account, the calculated

targets and water body-specific Maximum Allowable Inputs will be optimised and lead to

MOF, Alm.del - 2017-18 - Bilag 35: Rapporten fra det internationale ekspertpanel om evaluering af de danske marine modeller

minimal waste of resources. For purposes of intercalibration, a robust typology can be

based on the results of the water body-specific analyses.

Choice of indicators:

Chlorophyll a is a generally accepted and intercalibrated indicator

of phytoplankton. Kd, as a measure for macrophytes and angiosperms, has certain

limitations. The Panel recommends building on recent efforts towards comprehensive

modelling of eelgrass in order to derive a better indicator of macrophytes, but to keep Kd

as a proxy meanwhile. The other indicators used in the statistical modelling address

important ecological questions, but are not mature in the sense that they lack a clear

quantitative relation with nutrient loading. The Panel recommends leaving them out of

the present modelling and developing targeted modelling directed at their incorporation

into the indicator system.

Statistical modelling:

The Panel sees great merit in the strategy to maintain two

independent lines of modelling, one based on statistical data analysis and the other

based on mechanistic modelling. The Panel recommends reorienting the statistical

modelling towards optimal estimation of the long-term slopes of the indicators on nutrient

loading in a cross-systems analysis way and keeping in principle both N and P loading

as explanatory variables. The Panel recommends elaborating the uncertainty analysis in

the statistical modelling and suggests that this will be facilitated when a single cross-

system advanced modelling approach is chosen.

Mechanistic models:

The mechanistic models are state-of-the-art, both in terms of

numerical technique and included processes. They are powerful tools for providing a

sound scientific basis for the implementation of the WFD in Denmark. A shortcoming is

that they do not cover all water bodies. As a consequence, different approaches were

used for the definition of reference conditions, targets and MAI in different water bodies.

We recommend extending a mechanistic modelling approach to as many water bodies

as possible to ensure that, in future, a uniform methodology can be used for the

definition of water body-specific MAI.

Methods to derive targets and MAI from the models:

The Panel recommends

simplifying the calculation procedure by removing the averaging steps between models,

between indicators, between water bodies within types and between water bodies on a

regional basis. In this way, the differences and correspondences between modelling

approaches, indicators and water bodies will become clear and can be further analysed.

Cross-checking of results of the statistical and mechanistic model approaches in

systems, where both are available, will form a basis for extrapolation to all systems. The

Panel recommends deriving one MAI per water body in this way and only deciding in a

later phase on regional averaging or lumping, when scientific results are translated into

management actions.

River basin interactions:

River basin models allow calculating the load reduction

potential of nitrogen and phosphorus for each river basin, the development of water

body-specific nitrogen and phosphorus load reduction scenarios and cost estimates.

Further, they allow addressing seasonal load and limitation patterns. The Panel

recommends a combination of river basin and coastal water models to enable the

development of water body-specific optimised management concepts that consider both

nitrogen and phosphorus.

International approach:

The technical WFD implementation guidelines force similar

approaches in all member states. As a consequence, requirements, modelling and

challenges are similar in different countries. Further, the WFD asks for an intercalibration

and harmonisation of targets with neighbouring countries. Therefore, the Panel

recommends a co-ordinated joint scientific approach, especially between Denmark,

Germany and Sweden.