Introduction

This chapter discusses the theoretical basis underpinning a functional classification that covers all wetland types within Europe and outlines the rationale behind its structure by relating the classification development to policy and management needs identified in the previous chapter.

The fimctional classification developed for this thesis uses four core components; biogeographical type, geomorphic setting, water source and hydrological regime. These describe both the hydrogeomorphic location of the wetland within the landscape and provide a user with an indication of the wetland’s potential to perform a certain function. The term user is defined within this study as any individual or institution, being either governmental or non-governmental, that has an interest in managing wetland ecosystems. It is envisaged that a user of the functional classification is interested in managing wetlands at a catchment or regional scale. The functional classification provides pertinent information to a wetland manager at a site scale but the functional information provided treats the wetland as a single entity and does not take into account the functional variation within a site. As a result, the functional classification is a more effective tool at comparing the functional behaviour between wetland sites or understanding the wetland functional resources at a catchment or regional scale.

Biogeographical type reflects the climatic and habitat types that characterise the region where the wetland is located. It is vital that any classification covering an area as extensive as that of Europe possesses a regional element within it to take account of the significant variations both in climate and habitat. A biogeographical classification was chosen to fulfil this role within the functional classification, because the recognition of both climatic and habitat variation provides a direct link to ecosystem processes that control functioning. The geomorphic setting component of the classification indicates the location, within a landscape, of a particular shape of land surface, such as a depression, slope or channel. Water source describes the combination of water inputs to the wetland system. These include such inputs as groundwater, surface runoff, precipitation, and inundation. Hydrological regime indicates the duration and frequency of flooding. The combination of these four components should allow a detailed classification of all wetland types

within Europe. Hydrogeomorphic locations that are similar in functional performance are

grouped so that the potential functioning of a wetland can be inferred directly fi’om the classification.

2.2. Theoretical basis for classification

As discussed in section 1.25, wetlands naturally perform certain actions that are termed

functions. These functions result in a perceived value for society. Chapter 1 identified the merit in viewing a wetland landscape in terms of functional units, concluding that the approach gave significant added value to management and decision makers. It was shown that although few people dispute that wetlands have many and varied values, there are a lack of consistent, accepted methodologies to determine these values (Mitsch and Gosselink, 2000). A functional approach that separates a wetland into different units and therefore different value units provides a realistic assessment of wetland ecosystems and as a result allows more appropriate management strategies to be developed.

The amount and quality of information available for an assessment of functioning has direct bearing on the degree of certainty that can be attached to a statement about how a wetland functions. If sufficient money and time are available for a detailed research project then the degree of certainty attached to statements about how a wetland functions have the potential to be very high. Alternatively if the data availability are limited, such as topographic maps only, and the money and time available for the assessment is also limited, then the degree of certainty attached to a statement of wetland functioning is potentially much lower.

Section 1.24 identified the significant variety in potential users of wetland assessment techniques and the large range in activities which these users are involved in. These range from wildhfe trust site managers to governmental bodies involved in catchment management. Arguably, the type of information and the degree of certainty in statements of wetland functioning need to cover an extensive range if all potential user requirements are to be met. The degree of certainty of a statement of wetland functioning, the amount of time available and the budget accessible to a manager or decision maker to undertake an assessment, will determine the type of application they may use. During the development of the classification, and the review of activities of potential users, three levels of application have been identified which cover the range of detail that are required witiiin a wetland evaluation system (see Table 2-1).

Table 2-1 - W etland A pplications

A ssessm ent type T ype o f fim ctional statem ent generated and degree o f certainty

attached to i t

She monitoring and research Actual fimctioning - H i ^ certainty

Functional assessment procedures Actual fimctioning - Medium certainty

A site research project or fimctional assessment procedures adopt methodologies which determine whether fimctioning actually occurs within a wetland system. A site research project achieves this by monitoring ecosystem processes, structure and their interaction, to determine fimctioning. This type of investigation is very costly and must be carried out over a significant period to address the seasonal nature of wetland fimctioning. In contrast, fimctional assessment procedures are less costly and time consuming, and use the combination of background data and a site visit to determine fimctioning.

As discussed, in section 1.263, fimctional assessment procedures have been developed for Europe and are designed to assess the performance of one or all fimctions that may occur in a river marginal wetland ecosystem (WERG, 1998). The FAEWE procedures use the apphcation of knowledge gained through scientific research to identify controlling variables or indicators of the processes that influence ecosystem fimctioning. A user of the procedures records these indicators in the field and then follows a decision tree, utihsing the data gathered, to generate an assessment

outcome. The outcome gives an expression of whether the fimction is ‘definitely being

performed’, ‘definitely not being performed’, or ‘being performed but only to a small degree’ (WERG, 1998). This type of assessment examines whether fimctioning actually occurs but the degree of certainty, although described as “definitely being performed”, is not as high as that of a site research project because relationships identified at a range of wetland sites are applied to new sites which may have received no previous investigation. However, the FAEWE procedures do allow a relatively quick and cheap form of assessment to be undertaken, providing a user with information about processes and functions.

The type of assessment that the functional classification can provide is different from that of a site research project and that of the functional assessment procedures. Both of those methods determine whether functioning actually occurs because of the amount and quality of information gathered. It has been identified in Chapter 1 that in contrast to these approaches a more simplified form of assessment that is rapid and very cheap to use is required. Decision makers and managers which deal with larger scale assessments, such as regional or catchments, cannot afford to visit every wetland site and make an assessment of the actual functioning that is occurring at that site, even though that would be the ideal. In reality, managers often have to make decisions with little or no information on the functioning of wetlands within a region or catchment. Examples of when a functional assessment application developed for a catchment or region could be used is through the appliance of the EC Water Framework Directive (2000/60/EC). Within this directive river basins are assessed in regards to their ‘good ecological quality’ so wetland areas within a river catchment would be included within a catchment wide

assessment. Functional data relating to wetlands would be useful for bodies implementing the Water Framework Directive as it is provides relevant information on ecological quality and water chemistry.

The functional classification does not only provide structure to decision making it also allows an assessment to be made that identifies the potential for a wetland to perform a function. This information provides better understanding of wetland functioning within an area and enables a user to focus their attention on key wetlands. For example, if a user was concerned with groundwater abstraction within a region, and the affect it was having on groundwater levels, then they may be interested in wetlands which perform the function of groundwater recharge. To investigate every wetland within the catchment would be costly and time consuming. Therefore applying a functional classification to identify the wetlands that have the potential to perform groundwater recharge, could potentially save time and money. An example of where a functional classification of wetlands could simplify the identification of key wetland sites is within the work undertaken by the Environment Agency, UK. Part of their remit under the Water Resources Act 1991 is to ensure that all river systems in England and Wales are compliant with River Ecosystem Objectives. Each river must meet a certain target water quality depending on the uses for that river stretch. River stretches are designated as REl (excellent water quality) to RE5 (poor water quality). If water quality does not meet the objective set then a clear management plan has to be detailed to improve the situation. This management plan can include the role and impact riverine wetlands have on water quality. In terms of water quality, identification of the exact role a wetland plays within a river catchment is difficult to determine and highly costly. Utilising a functional classification, only the wetlands that are important for nutrient retention and nutrient export need be identified and assessed. Other wetlands that do not have a significant role in catchment water quality need not be investigated. Without the use of a functional classification to focus attention on key wetlands which have the potential to perform certain functions then all the wetlands withm the catchment would require investigation.

As well as the accuracy, time and cost difference between an assessment that looks at whether a function actually occurs or not, as opposed to an application that assesses the potential of a wetland to perform a function, a conceptual difference has also been identified.

The difference between a determination of whether a wetland has the potential to, or actually

does, perform a function, or from here onwards between potential functioning and actual

functioning, depends on the information that is available on the various wetland ecosystem structural elements. Table 2-2.

Table 2-2 - Conceptual and practical differences betw een type o f functioning

Type o f Functioning E cosystem structural elem ents

investigated

Tim e and cost o f assessm ent

Actual Geomorphology, hydrology, flora, fauna

and anthropogenic impacts

Slow and expensive

Potential Geomorphology and hydrology Fast and cheap

If a detailed assessment of functioning is needed then an assessment of actual functioning will

occur taking into account all structural elements. However if a rapid appraisal of wetlands is

required then an assessment of potential functioning should take place.

A determination of potential functioning is different from that of actual functioning

conceptually, because it isolates the relationship between the structural elements of geomorphology and hydrology, and the ecosystem processes, in order to determine the likelihood that a function is being performed.

A determination of actual functioning, within a wetland ecosystem, considers the processes

interacting with ecosystem structure, including the elements of fauna and flora, and with anthropogenic impacts.

Therefore, potential functioning is defined as the possible interaction of ecosystem processes

that can occur as a result of a wetlands hydrologie and geomorphic (hydrogeomorphic (see section 1.263)) characteristics.

In summary, a range of wetland applications are needed to address the disparate needs of the user community. Empirical site evaluations and functional assessment procedures are often costly and

time consuming but they do provide data on actual functioning and as a result fulfil the needs of

users that require focused, within site information. In contrast to this, applications are needed that fulfil the following criteria:

1. A cheap and rapid system more appropriate to a catchment or regional scale of assessment.

2. A tool that provides a clear structure to decision making whereby allowing the identification of key wetland sites.

The development of a functional classification can fulfil all these criteria if it is based on

hydrogeomorphic principles. Utilising the hydrologie and geomorphic information used for

classification an assessment of potential functioning can be inferred.