Recreation : Sensitivity assessment

An approach to sensitivity assessment

The following information regarding sensitivity assessment provides just one example of how such a review can be undertaken. It is not an example of the specific techniques and procedures followed by the Countryside Agencies, and in no way reflects the views and opinions of the agencies.

Assessing Feature Sensitivity

Sensitivity analysis has been carried out on coastal sites mainly to assess the possible effects of oil spills. More recently, a number of projects have been assessing the sensitivity of marine areas to recreational use.

‘Sensitivity’ was defined by Hiscock (1996) as ‘the intolerance of a habitat, community or individual of a species to damage or death from an external factor". It is important to distinguish between intolerance, (intolerance - the inability of a habitat, community or individual (or individual colony) or a species to cope with exposure to an external factor) which brings about death or reduces populations to levels from which recovery is impossible or very unlikely, and intolerance to damage from which recovery and survival may be possible with repair of the damage. Assessment of sensitivity therefore needs to take account of ‘recoverability’ – the ability of a species to return to its former status once original conditions return (MacDonald et al 1996). However, the Habitat Directive Regulations do not include characteristics of the activity within the guidance on assessment criteria and in addition some of these factors may not be relevant to the sensitivity of the site features.

Changes in behaviour, displacement from breeding or feeding grounds or long and short term disturbance may be important indicators of responses to stressors, but they may also occur as part of the natural long-term life cycle of specific species.

For marine recreational activities, it may be possible to assess feature vulnerability, (vulnerability - the exposure of a habitat, community or individual (or individual colony) to an external factor to which it is sensitive (Hiscock, 1996), both geographically (spatially) and also across time periods (temporal). Some organisms may not be vulnerable/sensitive to a particular action if they are frequently exposed to a particular stress. However, the same species in another location, which does not commonly experience this stress, may be sensitive/vulnerable because natural resistance to the stress or acceptance of the activity has not evolved. However, there is insufficient knowledge about the recoverability of many marine habitats and species that may be vulnerable to marine recreation.

Assessment of sensitivity to recreational use has typically focused on ‘spatial’ vulnerability – the existence of a species or habitat in a given location that is likely to be affected by a specified activity. This must take account of the time scale over which changes occur. For example, a recreational activity that has the potential to cause damage may only occur when the species at risk is absent. As recreational activities are now carried out throughout the year, impacts may increase particularly on species that locate in the area on a seasonal basis. For example, improved wetsuit technology has extended the season for immersion sports into the winter season. Often such activities will access the water via intertidal sand and mudflats. At high tide potential effects will be limited, but at low tide these mud flat areas are used by wintering waterfowl for food and rest. Disturbance may occur to species that only use the site during the winter period.

The potential for an increase in the conflict between nature conservation interests and recreational interests thus becomes greater as new and seasonally unrestricted recreational activities introduce new stresses into the marine environment. Conflicts between innovative new uses and established ones may bring about changes in the location of activities and so spread the stresses on marine species and habitats to new areas. However, there is only limited understanding of these effects as species and communities can be highly sensitive to some stresses and not at all sensitive to others.

Sensitivity assessment is a flexible approach that can be applied at any geographical or temporal scale. It is consistent with both sustainable management and the development of sustainability indicators. The key feature of sensitivity assessment is that it takes a holistic approach to the impacts of activities on the environment, identifying those areas most susceptible to change (whether positive or negative). It considers the tolerances and thresholds of features to different types and scale of activity and is flexible to emerging trends.

Sensitivity assessment should be an integral part of any project planning process and is not scale limited. It has demonstrable benefits in that it provides the baseline upon which more detailed studies and assessments can be carried out (perhaps at EIA level if necessary).

Some approaches to sensitivity assessment use a flow diagram template against which case studies can be tested. This provides a pathway through the process of decision making, making it easily understood. It relies on a simple set of questions asked at key points. The response provides a particular pathway to the next step of the process.

Sensitivity assessment can also help to identify the most critical assets within an area to be protected whilst allowing sustainable management for the optimal (but not maximum) use of marine resources. The more comprehensive and reliable the information which feeds into the assessment process, the smaller the critical areas identified are likely to be. The critical areas are of course the core areas for management and will be based upon sensitivity of the features and existing and potential activities within the area as well as external factors.

The Process of Sensitivity Assessment

It is generally agreed that the following questions need to be asked in order to identify the levels of sensitivity of a feature and the vulnerability induced by recreational activities.

What are the Characteristics of the Feature?

The size, abundance, rarity, robustness, distribution, and social importance of the feature need to be reviewed. The level and format of the information which is currently available will dictate the effective completion of this step in the process. relevant authorities, site managers and recreational participants should be aware of issues concerned with quality assurance of the information base and questions need to be asked about the following:

  • the source of information

  • reliability of data and information

  • completeness of data/information

  • levels of understanding of this information

Once these questions have been considered, if lack of information restricts the decision making process further, information requirements should be highlighted and appropriate research undertaken. It is especially important to identify both Characteristic Species ( special or especially abundant in a particular situation or biotape. Characteristic species should be immediately conspicuous and easily identified (based on Hiscock & Connor, 1991 in Hiscock, 1996) and Keystone Species (biologically structuring species that are vital to the ecological integrity of communities, and whose absence would cause the community to significantly alter, dysfunction or disappear (Masters & Gee, 1995).

To What is the Feature Sensitive?

Relevant authorities, site managers and others involved in the policy process should be aware of the possible implications of natural processes and human uses of the site and their effects on its sensitivity. Furthermore they should take steps to assess the vulnerability of the site and its species. This will be dependent upon the available data and information. Consideration should be given to the quality of the information and if necessary further research should be commissioned to aid the development of policy and practices.

What are the Characteristics of the Activity?

For each mSAC site, consideration should be given to a range of both natural and human criteria. These include the area’s size and extent, naturalness and fragility. Specific recreational issues include diversity and levels of activities, aesthetic appeal, cultural significance, etc.

What are the Levels of Acceptable Change (LACs)?

The levels of stress imposed on a site, feature or community will have implications for its overall stability. High species richness is maintained in communities at intermediate scales of disturbance. However, additional levels of stress may cause damage or disruption to the feature or community. It is essential to establish the limits of recoverability with respect to specified disturbances for natural and managed communities. The extent to which a community may be disturbed before it shifts to a less desirable form should also be assessed. The sensitivity assessment should provide a basis for judging the probability and acceptability of these threats. The checklist boxes below summarise the main issues to be considered:

  • What features are located in the site (both habitats and species)?

  • Is the value of the habitat geological, archaeological or geomorphological or as a home for keystone species?

  • How resilient are the habitat’s geological, archaeological and geomorphological features?

  • Are keystone species valuable at a community level or at an individual species level?

  • To what extent do external stresses, including those caused by recreational activities, affect the habitat, species or community?


  • Is the habitat/species able to cope with stresses (is it robust?)

  • Is the habitat/species able to recolonise following exposure to an external factor?


  • Is the species able to avoid the effects of such exposure by temporary emigration or withdrawal into shell or shelter?

  • Is this ability to avoid the effects driven by other factors, eg proximity of other populations, barriers to spread?

Figure 2 Recreational Issues to Consider

  • Are human influences direct – physical damage, disturbance, degradation?


  • Are the levels of these impacts occasional, regular or constant?


  • Are human influences indirect, eg competition for space, water, quality, noise?


  • Are the levels of these effects occasional, regular or constant?


  • Where do these impacts take place?

  • Are the locations static or do pressure points change depending on the season?


  • Are they land side or water side effects?

Sensitivity levels

The above process should provide the following information

Assessment of sensitivity of a habitat or species, at the level of the species' ability to cope/recolonise/avoid.

Identification of the source of disturbance and assessment of its effects on the habitat and species’ sensitivity. For example, if the stress is repeated but the organism has strategies for temporary avoidance, the species suffers damage but is able to cope.

Once this process has been completed, it may be possible to devise a scale of sensitivity to summarise the findings. Having identified the component impact associated with a maritime activity (a sensitivity factor), it may be possible to assess the factor intensity, i.e. the magnitude of a factor on a pre-defined scale.

In practice, for many species it will not be possible to assign their sensitivity to more than a simple scale of neutral, sensitive, neutrally sensitive or damaged, and so for many sites the simple allocation of species, sites, features and communities to a sensitivity scale of benign, neutral or damaged will be the initial level at which sensitivity can be assessed. There will be overlapping sensitivities, thus in a specific area one species may be very sensitive to particular recreational activities whereas others are unaffected. Judgements need to be made about the geographical resolution to which sensitivities will be applied. Nevertheless, it is essential to recognise that habitats, processes and organisms are often finely tuned to disturbance, but that once a sensitivity threshold has been crossed, recovery may be slow or impossible.

It should be possible to use the following or similar statements to judge the level of sensitivity:

The action positively effects the process or organism.

eg marina construction provides a new rocky habitat for limpets.

The habitat, processes or organisms are sensitive to short term disturbance, eg birds fly from feeding areas when disturbed by a passing vessel, then settle back to the earlier state.

If a disturbance is repeated or sufficiently intense, organisms move to alternative areas, although they may re-occupy the area if the source of disturbance is removed, eg a change of wind direction requires change in launch points or accidental spillage of fuel causes localised bird mortalities. This level of disturbance may also affect organisms’ breeding rates.

The habitat, process or organism is sufficiently sensitive that if further stresses from other activities occur it will be seriously damaged and become fatally sensitive. For example, a small breeding population already adversely affected by climate is disturbed by increase in water-based recreation during breeding season (this is probably sub-lethal).

The habitat, process or organism is so sensitive to this effect that it will die or change irrevocably.


To assess the possible negative or positive implications of recreation on specific marine features or species, it is important to have an understanding and appreciation of the often variable and complex nature of these features.

It is important that observed changes are not automatically attributed to human disturbance.

To place observed changes within the context of natural variations over time and the variety of human uses of the coast it is important to make an assessment of the sensitivity, recoverability and vulnerability of designated site features.

It is also important to distinguish between ‘intolerance’ to an action from which recovery is impossible and 'intolerance' to an action from which recovery and survival may be possible.

Sensitivity assessment provides a robust, flexible and holistic approach.

The Marlin project supported by the Marine Biological Association is developing a biological sensitivity database. Its website is