Fen Management Handbook - Scottish Natural Heritage

Mowing can be considered as mechanical grazing; it retards plant succession and
opens up the surface to allow seed germination and growth, but grazing has a
number of advantages over cutting:
– Lack of arisings: no bulky material to dispose of.
– Low labour requirements.
– Low maintenance: cattle cost less than machinery, do not require much in the
way of fossil fuels, and traditional breeds can be very hardy.
– Continuity combined with variety of physical structure: at this level of grazing,
some areas of fen are left untouched for long periods, while others are opened
up. The grazed areas vary from year to year. This physically varied community
would be very difficult to produce mechanically, and should be advantageous to
a variety of invertebrates. Grazing at these low levels has not affected the plant
community composition.
– Creation of additional microhabitats: droppings and water-filled hoofprints add
valued structure at small scales.
Nothing is perfect, however. Attendant disadvantages which need to be dealt with
include:
– Site structure: not all fen sites are suitable for grazing animals. One major
requirement is for refuge areas which can be used at times of high water and
flooding. At Bure Marshes there are several spoil banks which remain dry, and an
adjacent field on higher ground is leased.
– Need for infrastructure: some capital investment is needed for handling
facilities (typically a pen and race), bridges and fencing. Water-filled ditches, as
at Woodbastwick, make effective wet fences.
– Welfare considerations: traditional breeds such as Highlands are very hardy,
can cope with wet conditions without being vulnerable to foot and parasite
problems and hence need little veterinary input. Less hardy commercial breeds
seem unable to obtain sufficient nutrition from fen vegetation (the Woodbastwick
animals have had one supplementary hay bale in eight years). However, regular
checking is required.
– Scrub: cattle at these grazing levels do not prevent scrub growth, although they
can damage it by rubbing and limited browsing. In order to prevent excessive
scrub development, bushes are cut individually with brush-cutters. This allows a
scattering of scrub to be maintained within the fen (typically about 5% scattered
cover), necessary for a variety of fauna, including song perches for sedge
warblers. Cut material is not produced in large quantities at any one time, and
can be cut up and left to rapidly decompose within the fen, producing another
microhabitat.
In effect, the combination of cattle and staff with brush-cutters produces a “supergrazer”
and a type of “semi-natural” management for this semi-natural habitat.
136