Introduction to the guidance manual
12. Ecosystem dynamics
Targets should take into account ecosystem dynamics, e.g. successional changes on sand dunes and localised loss of woodland areas due to natural processes. However, it is acknowledged that it may sometimes be difficult to distinguish between such 'natural' changes and changes caused by human induced factors. The key to dealing with natural change is to be clear about what is important about the site. In order to illustrate this, two examples, for woodlands and coastal features are given below.
12.1 Woodlands
For some woodland features of interest, natural change could be as damaging as direct human intervention. If a site is important for butterflies associated with open space, 'natural change' that leads to the glades scrubbing up will put the butterfly feature in unfavourable condition. In another site important lichens might occur on just six specific veteran trees: if wind blow uproots the trees (leaving them lichen-side down) the lichen feature becomes unfavourable.
Where the interest feature is more general, for example the semi-natural woodland community the impact of 'natural change' may be viewed more benignly. A shift in the relative abundance of vernal flowers or in the relative dominance of oak versus other site native trees may be acceptable, or at most slight changes in management may be recommended to off-set it, without the need to alter the overall condition assessment.
A third situation is in sites where our aim is to develop as near-natural a woodland state as we can under the prevailing conditions. Since we do not know what 'near-natural' actually is in 'state' terms we must judge success by the degree to which natural processes operate. Almost any composition / structure is acceptable. Natural change is positively welcomed as a sign of success. Thus if the wood blows down (as many did in the 1987 storm) this is not an undesirable event and does not make the woodland feature unfavourable.
12.2 Coastal
A key element of the scientific interest of coastal habitats such as sand dunes, soft cliffs or salt marshes is the presence of active coastal processes, which influence the development of a range of natural successional stages. Many of the coastal habitats which are Annex I features are directly related to the interaction between natural processes and vegetation, this is reflected in titles such as 'shifting dunes with Ammophila arenaria', 'annual vegetation of driftlines' and 'Salicornia and other annuals colonising mud and sand'. Coastal habitats are often of interest themselves for active geomorphological processes.
Moreover, all coastlines are naturally dynamic. Despite the many modifications to the coast, these natural processes continue and are important in determining the overall condition of habitat features. Understanding how the features of a site adjust in response to these processes poses a particular challenge for conservation. A functional coastal ecosystem must have the capacity to change, and designated sites must be considered in a wider context.
While, for many coastal habitats, dynamic change is a natural and necessary process, it is also often what human activities are intended to reduce or prevent. Activities such as mechanical beach cleaning, building of structures (e.g. groynes or even offshore breakwaters), or land reclamation can affect natural processes or prevent a coastal system from responding to natural events. In other cases, activities elsewhere in a coastal cell may not even be on the site which is being assessed - which can lead to difficulties in judging what factors (natural or human induced) are causing change.
In many cases, it is the absence of artificial structures or operations that indicate that natural processes are able to operate. The presence of structures or operations that are clearly having a detrimental effect on the feature through the interruption of natural processes should, therefore, be recorded, as these will indicate that natural processes are restricted in some way. Whilst this goes against the guidance in section 9.1, it is difficult to provide hard and fast rules for all situations. In the circumstances described in this section, recording structures or operations would seem to be sensible, assuming the feature being assessed is a dynamic process, and the coastline is a manifestation of that process. If the feature is assessed as unfavourable, and there are no obvious reasons why, it may be necessary to look beyond the site for the factors which are influencing the feature.
A change from one habitat type to another as part of a normal succession would not inevitably result in a verdict of unfavourable condition. This will be a matter of setting target ranges appropriately to take account of coastal dynamics. In some very mobile systems, the feature could even migrate beyond the site boundary. In addition, the effects of climate change may cause some habitats to migrate landwards. If this is recorded during assessment, the site boundary may need to be amended and the site re-notified.
Notwithstanding the foregoing remarks, natural coastal process events can be damaging to interest features. For example, a breach in a barrier bank could damage or destroy a coastal lagoon and its component plant and animal communities, with little chance of these being restored in the foreseeable future. The condition of the lagoon feature clearly then becomes unfavourable. We should not conclude that a feature is in favourable condition simply because it is the end result of coastal dynamics. Changes due to coastal dynamics and natural succession should be considered alongside the state of the feature when assessing condition.