HUMANS may not be responsible for much of the perceived damage to wetland
bogs, and conservationists may be misguided in their attempts to restore them to
their 鈥渘atural鈥� state. A study of a wetlands area in Lancashire reveals that it
began drying out long before humans arrived.
鈥淐onservation planning surely has to deal with these complications,鈥� says
David Wilkinson of Liverpool John Moores University. He believes that
conservationists should not assume that there is one natural state for an
ecosystem that should be restored. Wilkinson points out that studies of ancient
pollen show that trees have grown in the now bare bogs in the past.
Raised bogs form in waterlogged environments where Sphagnum mosses
thrive, partially decompose, and build up in layers. These wetlands have been
drained for agriculture, mined for peat and damaged by pollutants. In recent
years, conservationists have tried to restore bogs by making them wetter, and
the wetlands have been cast as a vital habitat for unique plants such as
insect-eating sundews.
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Wilkinson and his colleague Stephen Davis constructed a history of Astley
Moss, a bog near Leigh, by counting the tiny shells of microorganisms called
testate amoebae that linger for thousands of years in soil samples. Since
different species of testate amoebae like different amounts of moisture, the
researchers could use the types of shells found in soil samples several metres
deep as an indicator of past water levels.
When they combined their results from the testate amoebae with radiocarbon
dating of the soil samples they discovered that the bog had started to dry out
around two thousand years ago. 鈥淭he first big change appears to be due to
climate rather than people,鈥� says Wilkinson, who had assumed that the decline in
Sphagnum mosses had started in the late 19th century, as a result of
exposure to nearby Manchester鈥檚 air pollution. The researchers presented their
findings this month to a joint meeting in Orlando, Florida, of the Ecological
Society of America and the British Ecological Society.
鈥淚t does give an interesting edge to the work we鈥檙e doing,鈥� says Mick Weston
of the Lancashire Wildlife Trust, which is trying to restore Astley Moss by
blocking drainage ditches and cutting down trees. But he adds: 鈥淚鈥檓 not sure the
information will directly influence the way we鈥檙e going to manage the site.鈥� He
says he鈥檚 pleased that the study shows the site is now as wet as it鈥檚 been in
two thousand years.
鈥淚 think the use of testate amoebae in peatland restoration has great
potential,鈥� says Barry Warner, director of the Wetlands Research Center at the
University of Waterloo in Ontario. He points out that only about half a dozen
scientists are currently doing this type of research.