Fen Management Handbook - Scottish Natural Heritage

At least three but ideally 10 replicates of managed and control areas are required to
demonstrate an effect so that natural variability between areas is accounted for and
any difference between managed and control areas can confidently be attributed
to management. Similarly to assess the effect of external environmental pressures,
such as lowering of the groundwater table due to abstraction, reduced flooding
frequency due to flood management works in the catchment, or an increase of
nutrients due to the installation of a sewage treatment works upstream of the fen,
monitoring will be required of both the external influence(s), and the way in which
these manifest through changes in fen flora and fauna.
10.2.2 What and where to monitor
Monitoring is expensive, and should be focussed to be as cost effective as
possible in getting the most informative outcome for the least effort. Deciding
why monitoring is to be undertaken will to a large extent determine what needs
monitoring, but how monitoring observations or data output will be used will also
influence what to monitor, and where.
Observations must be recorded at the right intensity (number of vegetation plots or
number of groundwater dipwells) and for the right duration (ideally during the same
season for five years) to validate subsequent number crunching. The statistical
validity of monitoring data depends on the size or magnitude of the anticipated
effect, and the number of samples taken. For example, effective monitoring of a
significant and readily observable change in vegetation due to nutrient enrichment
might require only five replicated samples in an area subject to enrichment, and
the same number in a control area on the same type of fen which is not subject
to enrichment. However, many more samples would be required to detect smaller
changes of biotic or abiotic parameters, particularly those which are intrinsically
variable, such as average stem length or increase in reed due to increased nutrients.
A pragmatic approach to this kind of situation is to start with a pilot survey. If the
resultant data is insufficient to demonstrate the perceived change, the sample size
may need to be increased. More detailed guidance on statistical validity and other
aspects of environmental sampling can be found in Ecological Census Techniques
(Sutherland, 2006).
The site environment can impose constraints on monitoring; some areas might have
to be avoided because certain habitats or species are susceptible to trampling for
example, or there is public access with the attendant risks of theft or vandalism.
10.2.3 How to monitor
Deciding on how to monitor should be driven by ‘why, what and where’ and
available resources. It is essential to think through the whole monitoring plan so
that the correct information with the right level of precision is obtained, and can be
carried out throughout the monitoring project. Important to consider are:
– Ensuring the health and safety of the people associated with monitoring. A
detailed risk assessment should be undertaken to identify risks such as drowning
associated with deep water or floating rafts of vegetation, water-borne diseases
such as Weil’s, poisonous vegetation such as giant hogweed, and animals such
as snakes. Given the potentially hazardous and often remote nature of fens, the
risks associated with lone working should be taken into consideration.
– Available resources: money, time, assets (e.g. hardware, computer, etc).
– The technical and practical abilities of the people who will be implementing
the monitoring strategy, and those who will be interpreting results or
implementing management based on the data obtained. Limited abilities may be
a constraint, but there are few methods or techniques which cannot be mastered
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