by Paul Hope
Greywell tunnel is a disused canal tunnel on the Basingstoke Canal in north Hampshire. The 1,124m long brick lined tunnel was constructed in tandem with the canal between 1788 and 1794. The tunnel is approximately 5m high and has a maximum width of 4.5m. It was excavated through an area of changing geology from Hampshire chalk through Reading beds into London clay. There was a partial collapse in the tunnel during the 1930s and a further fall during the 1950s that left the bore of the tunnel blocked about 800m from its eastern entrance and at 130 m from its western entrance. Bat friendly grilles prevent public access to the site.
Greywell tunnel is a disused canal tunnel on the Basingstoke Canal in north Hampshire. The 1,124m long brick lined tunnel was constructed in tandem with the canal between 1788 and 1794. The tunnel is approximately 5m high and has a maximum width of 4.5m. It was excavated through an area of changing geology from Hampshire chalk through Reading beds into London clay. There was a partial collapse in the tunnel during the 1930s and a further fall during the 1950s that left the bore of the tunnel blocked about 800m from its eastern entrance and at 130 m from its western entrance. Bat friendly grilles prevent public access to the site.
Greywell tunnel has long been known as an
important site for hibernating and swarming bats. It was designated a SSSI for
bats in 1985. Hibernation surveys are conducted from a boat by a team of up to
five surveyors. As you work your way into the tunnel light from the portal
becomes a distant dot. During hibernation counts many of the bats encountered
are hanging against the brick lining, however a high proportion are often
packed into crevices and openings in the brickwork left during the tunnels
construction. Within crevices it’s sometimes a matter of counting ears and feet
to get as accurate a count as possible and on occasion it’s not possible to
record bats to species.
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| Natterer's bats at Greywell. (c) Roy Champion |
Natterer’s bat is the most commonly
encountered species (highest count of 569 in 2013), Daubenton’s bat is also
regularly recorded (highest count of 69 in 1986). We also often record whiskered,
Brandt’s and brown long-eared bats. The count this January gave some very
exciting results. We had our second highest count for Natterer’s bat in the
eastern end (564) and our first ever record of a greater horseshoe bat. The
horseshoe bat is an excellent record for North Hampshire. Bat Group records
show it is the seventh on record; this includes two records for Winchester from
the 1940s.
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| Greater horseshoe bat at Greywell. (c) Roy Champion |
Sadly after over 30 years of monitoring at
the site, future regular monitoring is threatened by a recent move by the
owners Hampshire County Council to declare it a Confined Space. Now surveys can
only be conducted once every two years due to the excessive costs of gas
monitoring equipment and a rescue team stationed outside the tunnel. We do not
feel that this is often enough to provide adequate data resolution for the SSSI
condition assessment, but Natural England have said that it will be sufficient.
Being one of the people who encouraged this site to be saved for bats at a time when number of other interests were pulling in different directions, it is pleasing that hibernating bat numbers remain buoyant there. It is a very important site.
ReplyDeleteThe "confined space" trick is being widely used by those who would push for a different use of specific features, other than the best possible use - a hibernating bat roost. By stopping legitimate survey these individuals hope the site will be forgotten about or the survey results will not justify protecting it against alternative and damaging uses such as returning it to a through canal.
The MoD have been using this reason for preventing survey access in East Anglia.
I would like to see BCT properly explore this newish restrictive aspect and come up with a legal way that bat roosts on SSSIs can still be legitimately monitored - perhaps by providing appropriate training and purchasing a set of equipment that can be loaned around the sites.