These criteria tend in some instances to merge or even overlap with each other, and
they often run
parallel and so are additive; but sometimes there is mutual incompatibility, e.g. rarity is seldom
compatible with typicalness or diversity with homogeneity, and while naturalness is usually rated
highly, the Norfolk Broads are artificial in origin yet must be regarded as one of the most important
wetland areas in Britain. The application of these criteria in site assessment is a complex matter,
difficult to rationalise or explain simply. In general, for the first five, the larger the score the
higher
the quality. Large size does not necessarily confer high quality if there are no other desirable
features, but does so in combination with other attributes such as marked diversity or presence of
rare communities/species. Conversely, marked diversity may not rate highly if the area involved is
too small. However, a rare and fragile type of ecosystem can be extremely important, even if it is
small and fairly uniform. Site assessment often involves variable weighting of criteria, i.e. they are
not all of equal importance, nor everywhere of the same relative importance. Some criteria cannot
be used on their own, and while some are independent others are inter-dependent. Ideally, to
qualify as a key site, an area should rate highly according to as many criteria as possible, but few
sites rate highly in all qualities; while a majority of key sites have been selected for a high quality
conferred by a combination of features, some have been chosen for a single important attribute.
Much depends on the choice available within any major ecosystem or community type.
The best way of discussing these criteria and their application is to take a specific
example of a
site which has long been accepted as a classic area of wildlife and habitat in Britain, and to
analyse why it is so highly valued.
The North Norfolk Coast is a maritime ecosystem complex containing extensive examples
of sand
dunes, salt and brackish marshes, shingle beaches and inter-tidal flats, largely unmodified by man.
The physical and biological processes involved in shore accretion and erosion are especially well
demonstrated, and classical studies have been made of the dynamics of coastal physiography and
plant succession, and of the relationships between the different habitats and their vegetation. The
vegetation is rich in species, and there are especially large populations and extensive communities
of certain plants which are characteristic of salt marshes in this part of Britain: a number of rare
species occur, including some at the limits of their British range. This coast is an important
breeding ground for certain coastal and brackish marsh birds which include big populations and
interesting communities of rare species. In the autumn and winter, it is a major haunt of passage
and wintering birds, especially waders and wildfowl. The invertebrate fauna is large and includes
many rare species. Some of these features, such as the colonially breeding terns and the sheets
of sea- lavender in flower are sufficiently spectacular to excite the lay public and the whole area
serves an important educational function over a wide range and level of interest.
The aspects of importance are clearly inter-related, but there is an over-riding aspect,
the total
diversity of the area, which gives it an especially high value. This includes not only the diversity
in
range of major coastal features but also in species-richness of certain communities. The extent of
the area and particular communities, the size of the populations of certain species, and the
presence of many rare species are notable features. The natural state of the whole ecosystem is
unusual and the range of variation also encompasses that characteristic of such coastal formations
in this part of Britain, so that it may also be regarded as representing typical features. The research
and educational value of the area is very high and the degree of documentation of many features of
scientific interest over a long period gives an additional measure of importance. The physiographic
interest of this coast is a further factor, although this aspect of nature conservation is not
specifically considered in the present review.
These attributes of the North Norfolk Coast thus provide standards against which examples
of
similar ecosystems can be judged, and the kinds of values involved can be applied more widely to
the assessment of other types of ecosystem. To continue the discussion in more general terms,
similar sites are compared to see which scores most highly for particular features or combinations
of features, the aim being to produce a final evaluation of the overall quality of each in relation
to
standards for its type, i.e. position in the abstract ecological classification. The judgements
involved are comparative and therefore relative, and they concern what is available, which often falls
well short of the ideal. The varying use and emphasis of different criteria according to formation are
discussed under the accounts of the formations themselves.
The comparative assessment of sites could in theory be made more objective by applying
a scoring
system to the above criteria, so that the total score for a site would be a measure of its overall
quality. While it was found possible to apply this procedure locally, or within a limited range of
habitat (it was done in Coastlands) no attempt was made to develop a comprehensive scoring
system to cover the whole range of British ecosystems. Not only are there complexities difficult to
deal with, such as the frequent lack of independence of criteria, and the varying absolute and
relative values of different criteria according to requirements, ecosystem group and locality, but
basic information for different formations and sites is so variable at present that a scoring system
could not be evenly applied throughout the country. Nor is there a satisfactory logical basis for
allocating actual score values to different site features. While these problems may eventually be
solved by careful study of conceptual difficulties and intensive collection of field data, at the
moment any such attempt to quantify the process of selection for all key sites could only give a
spurious objectivity. It is nevertheless sensible to follow a limited quantitative approach when this
is
feasible and valid as for example, by counting the number of communities or species in assessing
such features as diversity. Recent studies, such as that by Helliwell indicate the kind of advances
in approach which may lead to a more consistent and satisfactory methodology of evaluation of
nature conservation interest.
Choosing the national series of key sites
So far, discussion has been limited to the processes whereby the respective merits
of two or more
sites of basically similar character are compared and the sites then arranged in order of relative
importance. There remains the more difficult task of choosing a series of the most highly valued
sites which will form an acceptable sample of the national range of variation in natural and semi-
natural ecosystems. Part of the problem may be approached reasonably objectively; given time and
resources, the field of variation can be charted and samples (reference points) identified and
described. The more intractable difficulty lies in the interpretation of the word 'acceptable' - for
this
interpretation must necessarily be subjective, since the ultimate purpose to be served is so broad
and varied that no simple definition is possible, and it cannot be related to any absolute standards.
There is some analogy with the methods of taxonomy, for the taxonomic categories that
are used
to describe the field of ecosystem variation are also the abstract units on which the selection of a
series of key sites is based. For instance, having grouped peatlands into six major classes of mire,
it is a natural consequence to select key sites which will represent each class. And since each
major class of mire is divided into a range of subclasses according to variations in climate,
topography, hydrology and floristics, it follows that each of these subclasses should be
represented in the series of key sites. The difficulty lies not in choosing between mire sites which
are obviously different in major features but in deciding how many to choose from a number of mire
sites which belong to the same major class but differ from each other in more minor features. This
is reminiscent of the basic taxonomic problem of deciding on the spacing of the reference points
within a field of continuous variation-should they be closer together or farther apart? At one extreme
one could select virtually all sites with semi-natural or natural ecosystems, so that no possible
minor variant could be omitted, while at the other extreme one could select so few sites that a
great deal of the field of ecological variation was left out of the series. Clearly, something
approaching the 'happy mean' is needed - but how does one strike the best point of balance ?
The series of key sites to be presented represents the point of balance in the collective
judgement
of a number of people, just as an accepted taxonomic system tends to lie somewhere between the
views of the 'splitters' and the 'lumpers'. A second major conceptual difficulty arising here is that
there is not one basis but many for a taxonomy of ecosystems. There is general agreement that
vegetation provides the best basis for such a system, but even vegetation may be looked at in
different ways. For instance, woodland may be classified according to species- dominance within
the tree layer, floristics of the subordinate layers, physical habitat factors (climate, topography,
soil) or management/ structural type. Often, these different parameters can be applied at different
hierarchical levels within a single classification, and when this is both possible and convenient it
seems a sensible practice to follow. These are different aspects of ecological diversity and, while
they often show a degree of parallelism, each has claims to be considered separately when the
choice of representative sites for the particular range of ecosystem variation is made. One is thus
faced with further questions, namely, which and how many specific bases of ecosystem taxonomy
shall be considered in selecting a series of key sites, and in what order of priority ?
The actual selection of a national series of key sites covering all natural and semi-
natural
ecosystems is in abstract a complex procedure, entailing in the choice of each site the appraisal of
a body of recorded information and the application of various criteria for assessment in such a way
that they become integrated as judgement is made. The description of the thought processes
involved is a lengthy business, entailing various rationalisations and discussion of abstract
concepts. Yet in reality, the procedure of site assessment and selection includes a number of
steps which are taken almost automatically, in the same way that a person crossing a busy street
makes numerous observations and calculations about his own motion and that of vehicles, without
ever thinking consciously about the matter. Moreover, in analysing retrospectively the processes
involved it is easy to claim a degree of logic and a sequential order of events which were not
followed in practice. For instance, the comparative assessment of sites and determination of
acceptable representation are not really separated in the manner indicated in this written
presentation, but proceed together pari-passu as survey progresses and knowledge accumulates.
And to a considerable degree, the criteria discussed under comparative assessment are also
involved in the election of a site to the national series; when the application of these criteria
indicates that a site is quite exceptional or unique, its selection automatically follows.
The position at the beginning of the present review was somewhat as follows. Over
100 NNRs
representing the six major formations and various subdivisions of these were already declared. It is
impressive that the original assessment of the great majority of sites proposed as NNRs in Cmd
7122 remains unchanged in the present review. It is, indeed, remarkable how consistently
unanimous a view is to be found amongst experienced field ecologists and naturalists about the
outstanding merits of many key sites. To the uninitiated it may seem that the manner of judgement
is an art rather than a science but, whatever the case, the standards show a considerable degree
of uniformity. The need for the Review grew not from any feeling that the established standards
required re- judging, but from an increasing awareness that if these standards were to be applied
consistently through the full range of ecosystems in Britain, a considerable number of other sites
had equally strong claims for addition to the list of key areas. In other words, as knowledge of the
range of ecosystems in this country increased, it became clear that there were many gaps in
representation of important types. In some instances it was obvious that sites which had newly
come to light were decidedly more valuable than certain others well known and already safeguarded.
People do not, in fact, usually go around thinking that this or that particular abstract
type of
ecosystem requires representation, but with the knowledge that, for example, A, B and C are
outstandingly good upland sites of different kinds, but that there are other sites of unknown value
which need examination. If upland site D is then found and looks good, the first question to be
answered is whether it is broadly similar to or different from A, B or C. If D is similar to one of
the
others, a decision is needed as to whether it is inferior or superior, and this depends on evaluation
of detailed differences. If D is markedly inferior it is dropped from further consideration as a key
site, but if it is only just inferior, it may be included as an alternative to the other. Should D be
superior to any other similar key site, it will automatically be included in the national series, and
its
rival will either be dropped or retained as an alternative. On the other hand, if D is quite different
in
main features from any other key site, one then has to judge whether it is sufficiently important in
its new features to justify representation in the national series as a further type of upland. There
is
a continual and cumulative process of comparison and selection or rejection based on serial
observations of a number of sites. It follows that those sites which one encounters first will tend
to
become standards, and this can be a source of bias. This kind of bias tends to diminish as
experience of number and variety of sites grows.
The process is complex in practice and depends at the outset on a sufficiently wide
knowledge of
the detailed character and range of national variation in natural and semi- natural ecosystems - in
short, an adequate field experience of vegetation and wild animals. This basic expertise naturally
increases as survey progresses. The more there is background knowledge and experience on
which to base the judgements involved in site selection, the more reliable and useful the process is
likely to be. The pitfalls are sometimes unexpected. For instance, it might be thought that there are
pedological and ecological grounds for representing all the major geological formations in the series
of upland key sites. Only field experience can teach that the difference between, say, the
Ordovician and Silurian formations per se is usually ecologically meaningless, and that it is far
more important to differentiate between the calcareous and non-calcareous rocks within each of
these formations.
While particular needs will be discussed under each major formation, the following
general
requirements for achieving the declared objective of the Review may be stated:
Selection of a series of sites adequately representing the national range of variation
in the following
ecological features:
Climatic
Biological
features dependent on local and regional gradients of climate. Local gradients of
climate are related especially to such topographical factors as altitude, aspect and
proximity to water bodies; whereas regional gradients are concerned with larger scale
tendencies such as the increase in oceanicity with distance west and decrease in mean
temperature with distance north.
Physiographic
Biological
features associated with major variations in land forms. Most diversity within this
class may also be analysed in terms of climatic or edaphic variation, but it is often useful to
consider physiography as an ecological factor in its own right.
Edaphic
Biological
features associated with major variations in physical and chemical properties of
soils and their parent materials, i.e. geological formations. Physical soil factors include
especially wetness (determined by soil porosity, angle of slope, configuration of ground,
water supply and evapotranspiration), while chemical factors include especially acidity-
alkalinity (pH) and availability of important nutrients, notably calcium, potassium, nitrogen
and phosphorus. There is a need to represent the complete range of soil types (identified in
terms of physical/chemical profile characteristics) associated with the whole range of
natural and semi-natural plant communities. Soil conservation is usually understood as
concerned with maintenance of fertility and carrying capacity, and, while this may be an
important requirement on some, it is not the case for every key site, and sometimes there
is a need to prevent nutrient levels from increasing. The motives for soil management are
different in nature conservation from those in agriculture.
Anthropogenic
Biological
features associated with major variations in system of land management by man.
These mostly represent varying degrees of modification of natural ecosystems by human
influence, including clearing of woodland and scrub, burning, grazing and ploughing; they
also include managed types of semi- natural ecosystems within woodland, grassland,
heathland, upland, wetland and some coastland.
Some
artificial ecosystems may have considerable conservation value, but it is usually felt
that on their own these have no strong claims to representation in the national series of key
areas, as in the case of plantations of alien conifers such as Sitka spruce. Sometimes an
artificial habitat eventually develops a semi- natural character and may then have stronger
claims to be considered in the selection of key sites, e.g. reservoirs, disused gravel pits and
quarries. Other essentially artificial habitats which develop a semi- natural character may,
from their very nature, be unsuitable for consideration as conservation sites on the national
scale, e.g. hedges, roadside verges and railway embankments, yet they may have strong
claims at the local level.
The biological features alluded to above include both communities and species of plants
and
animals. Ideally, at least one good example of every described plant community in Britain, and one
viable population of every wild plant and animal species should be represented within at least one
grade i or 2 site. It must at once be stated that achievement falls well short of this ideal. For one
thing, vegetational taxonomy based on phytosociology is incomplete and many plant communities
are not yet identified, while the description of animal communities has hardly begun and animal
species are so numerous that the problem of their representation cannot possibly be tackled
satisfactorily at the species level. Moreover, neither communities nor species are all of equal
importance, but their varying value (and hence claims for representation) cannot yet be properly
quantified.
At the risk of being repetitive, it is necessary to stress again that adequate representation
is not
synonymous with uniform or total representation of the field of variation. It is not the intention of
the
Review to advocate the safeguarding of every minor variant of habitat or community, especially
when these are isolated from more important areas. The main need is to ensure that all major
types are represented, and that all the really important sites are included. Sometimes, the
philosophy of ' as large a sample as possible' has been applied to certain fragile and/or rare
habitats, communities and species, especially when their international importance is high. This is
especially the case with the major concentrations of wintering wildfowl and waders, and colonial
breeding coastal birds, for which Britain has a strong international responsibility in conservation;
virtually all the areas with numbers of these birds above certain levels have been included as key
sites, though not all are grade I. Every effort has been made to avoid extravagance in the
compilation of the national series, and the final list of grade I and 2 sites is regarded as a
reasonable minimum.
The choice of ordinary sites has been judiciously limited, and whilst the Review has
taken some
account of research needs, it has done so to a varying degree. Many of the key sites chosen have
a known research value, which has been regarded as a significant attribute. Virtually all key sites
have a potential research value, and the series as a whole would give a great deal of scope for
research, but there has been no attempt to choose sites for a specialist research interest involving
experimentation. Some sites with ordinary ecosystems which have been the location of long-term
and intensive research projects may assume an increasing historical importance, e.g. Meathop
Wood, Lancashire, for International Biological Programme studies and Kerloch Moor,
Kincardineshire, for red grouse research. However, experimental research often places a premium
on such attributes as uniformity (for work involving sampling and replication) and accessibility, and
may involve considerable disturbance to the ecosystem, such as felling of trees or deliberate
removal of species. Since these criteria and activities are usually difficult to reconcile with those
discussed previously, it has been felt that the needs for research sites primarily of the experimental
type should be dealt with as they arise, for they are often highly specific and relatively short term,
as well as ad hoc and unpredictable. No attempt has therefore been made in the Review to cope
with them, or to foresee all future research requirements relating to semi-natural and natural
ecosystems.
Similar considerations apply to educational sites. For teaching purposes, convenience
of access is
often an important criterion, and these activities may create degrees of damage unacceptable
within a classic 'living museum' site, e.g. through disturbance of rare and sensitive nesting birds
or
trampling of fragile plant communities. Many of these educational needs can be better met by sites
of grade 3-4 or lesser importance, though features associated with diversity make many key sites
especially valuable for teaching ecology, and sites showing various classical features are obviously
the best demonstration areas for the phenomena in question. All sites are thus regarded as having
potential educational value, but the degree to which this can be exploited will depend on various
constraints, including both the requirements for management and the conditions of ownership.
Sites can be important in acting as reservoirs for species, including the genetic
diversity of these.
The general principle of selecting sites which include a range of phenotypic diversity in common
and widespread organisms is likely to cater for many requirements for living material which may
arise, ranging from the need for genotypically variable populations of species to parent stock for
propagation work of various kinds. The degree to which key sites will serve as reservoirs for the
natural dispersal of species must inevitably be variable and extremely difficult to assess, but the
potential is probably considerable.
Conclusions
The comparative assessment of sites within a related group has been shown to present
conceptual
difficulties in regard to the relative weight that should be attached to the various intrinsic site
features and to the different criteria which are applied in evaluating these features. The selection
of
key sites to give an adequate national series presents: a still more difficult test of reason. There
are
problems in achieving consistency in choice of sites to form a series within a single formation type,
e.g. woodlands, but it is still harder to prescribe the emphasis required in selecting one series of
sites compared with another, e.g. a woodland series as compared with a coastal series. Similarly,
how does one decide what weight to place on the representation of botanical and zoological
features in relation to each other ? What proportion of sites chosen should be of the classical and
rare or typical and common types ? How much prominence should be given to representation of
rare species or groups of species ? Should the disparity in total area between major formations
influence the numbers of key sites chosen to represent these ? For example, the combined area of
upland key sites is far greater than the total area of chalk grassland remaining in Britain; should
one therefore select a larger number of chalk sites to compensate for the larger area of upland sites
?
There arise many questions which cannot be answered with any precision or according
to clear-cut
rules. The problems involved are a matter for careful thought and considered judgement, having
regard to the need for a fair balance between the claims of the numerous and sometimes conflicting
requirements involved in the assessment and selection of sites. It is possible to find a consensus
of opinion on these matters amongst informed people working in this field who between them bring
to bear an enormous body of knowledge, experience and wisdom. This consensus of view has
repeatedly been sought, but the need for an adjudicator in cases of disagreement was realised and
one of the functions of the Scientific Assessor has been to resolve such difficulties by a personal
and often arbitrary decision.
In time, it may be possible to use more advanced techniques to achieve greater objectivity
and
consistency throughout in the selection of a national series of key sites. At present, the essential
scientific data on which computer analysis is based are far too inadequate for such a treatment to
give more than a biassed and provisional result, which could be misleading. Moreover, some
aspects of the whole process of assessment and selection are not yet measurable. In the
meantime, therefore, we have to rely on the computing and integrating abilities of the human mind,
whatever the shortcomings in this procedure may be. Since the purpose of the Review is ultimately
to satisfy a spectrum of human interests and activities, and is therefore heavily dependent on a
series of value judgements, it is, in any case, difficult to see how this process can ever become
completely objective. Some obvious forms of bias have to be eliminated as far as possible, as in
the case of local or regional patriotisms, and personal preferences for certain criteria or features.
However, it remains true that many of the judgements made are still subjective even when they are
collective, and this is particularly so in deciding when the national series of sites is adequate.
There is, in fact, no final way of answering this last kind of question, for it depends on values and
factors which cannot be quantified on any satisfactory basis. In the last analysis, the inclusion or
rejection of a site in the national series is based on informed opinion, and is thus open to argument
and alteration. Values are also prone to change in time, and future generations may look at things
rather differently. The present review is an attempt to prescribe the contemporaneous requirement
for conservation of special sites according to current values, views, information and constraints.
However elaborate the rationalisations which might be made to justify the way it has been done, it
would be wrong to disclaim the element of intuition involved, though one hopes that this is built on
awareness and experience.
The methods of evaluation and site selection used in the Review are therefore provisional
and
pragmatic, and dictated especially by incompleteness of survey information and the need to
produce a working report within a reasonable time. Urgency and realism rather than theory and
idealism have been the keynote of the operation. The issues involved are complex, and discussion
is not made easier by the semantic confusion which has arisen over a long period through the
habitually loose use of terms in ecology and nature conservation; these terms themselves now
have such breadth of application that they are often virtually meaningless, and require further
qualification. Within these limitations, an attempt has been made to explain the thinking behind the
Review, and the guidelines which have been developed in relation to the situation in Britain. The
results cannot be validated by reference to any absolute standards or economic base, but must be
judged more broadly in terms of their eventual long-term contribution to nature conservation.
