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Meeting
Report: Cardiff, 20 -22 November 1996
The International Scene
Case
sudies:
Introduction
Given
that the Mollusca are the second largest animal Phylum in terms of numbers
of described species and that 40% of the recorded animal extinctions
since 1600 are of molluscs, it is surprising that they do not feature
more highly in the consciousness of the wildlife conservation movement.
In a significant move to rectify this state of affairs, the first ever
conference to be dedicated to the conservation of molluscs took place
in Cardiff from the 20th to the 22nd of November 1996. Organised by
Mary Seddon and Ian
Killeen on behalf of the Conchological Society, the National
Museum and Galleries of Wales and the World Conservation Union (IUCN)
Mollusc Specialist Group, the first 2 days were based at the National
Museum and the last at Cardiff City Hall. Ian
Killeen has pointed out that the idea developed from a conversation
in a pub, but the conference can also be logically presented as a development
from the Alan Solem Memorial Symposium on the Biodiversity and Conservation
of the Mollusca held at the International Malacological Congress in
Sienna in 1992.
Between
80 and 100 delegates attended. Although most were from Britain there
was a sizeable and very important overseas contingent including Mariano
Gimenez-Dixon of IUCN, Phillipe Bouchet
(Musée Nationale d'Histoire Naturelle, Paris), Maria
Ramos and Rafael Araujo (Madrid),
Arthur Bogan (North Carolina), Vincent
Flores (Mauritius) and delegates from Finland, Kuwait, South
Africa, Belgium and Eire.
The
conference could be divided into general international scene setting
on day one; problems and particular cases (with an emphasis on Great
Britain and Ireland and on Margaritifera) on day two; and specific international
problems (and captive breeding) on day three.
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The
International Scene
The
major international organisations and legislation for conservation are:
IUCN.
197 land mollusc species are listed in the IUCN's 1990 Red List (see
Box 1), over half being island species. IUCN has some 800 Governmental
and non-governmental organisations as members, and aims to help drafting
national strategies, to provide management expertise and to help with
information on the status of species. The expert input is provided by
members of specialist groups like the Mollusc Specialist Group.
CITES,
the Convention on International Trade in Endangered Species of Wild
Fauna and Flora, 1975, is an internationally agreed listing of species
whose threatened status requires that trade in them is regulated, either
by a requirement for an export licence, or for an import licence, or
both. 134 states have signed the Convention. Species covered in the
appendices include 32 Unionidae, Achatinella species, the Tridacnidae,
Strombus gigas, Papustyla pulcherrima, and Paryphanta species.
Within
the European Community, the "Habitats Directive", which is aimed
at implementing the Biodiversity Convention agreed at the 1992 Rio Earth
Summit, institutes the designation of Special Areas of Conservation
(SACs), lists habitats and species of plants and animals which are rare,
endangered or vulnerable, and obliges member states to take action to
protect them. This is why the Countryside Council for Wales is required
to monitor, and take action to conserve, Vertigo angustior at sites
in South Wales, how the Spanish receive funding for work on Margaritifera
auricularia (now down to 20 known living individuals, its larval
host is probably the W. European Sturgeon, extinct in Spain), how funding
was acquired to move 600 square metres of Vertigo moulinsiana
habitat out of the line of the Newbury bypass, and how research into
human threats to the molluscs of maerl beds is resourced. Within the
UK, the Habitats Directive strengthens the protection provided by the
1981 Wildlife and Countryside Act and its schedules (e.g. most SACs
will already be Sites of Special Scientific Interest).
But
this legal framework is selective and there is a risk of concentrating
resources on "scheduled" species (even if they really should not be
so treated) at the expense of equally deserving cases. The law also
risks being sidestepped as Graham Oliver
pointed out, for example on the grounds that species"y", a recent segregate
from species "x", is not the scheduled species "x" - a warning about
being too closely bound to the taxonomy used in protected species schedules.
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What
are the priorities?
Molluscan
conservation efforts have predominantly targeted non-marine species
even though there are perhaps 80,000 living marine species compared
with 20,000 or so non-marine. This priority would appear justified:since
1600 there have been nearly 250 extinctions among non-marine molluscs,
and 4 among marine species. However, Mary Seddon
revealed that of 252 species extinct or extinct in the wild and 967
at high risk, N. American Unionids and island species were worst hit.
The non-marine element is more obviously exposed to threats, the whole
of their habitat being more accessible to human activity.
The
conservation of marine molluscs has to protect the fauna from less visible
threats than, say, deforestation - to some extent out of sight is out
of mind. Sue Wells pointed out that enclosed
bays vulnerable to pollution and coral reefs and mangroves required
protection. Protection from the shell trade was particularly important
with marine species - one million Giant Clams were removed annually
from the Philippines at the peak of trading. After habitat loss, alien
introductions are the primary cause of species extinction; this is well
demonstrated by Crepidula fornicata and Crassostrea gigas
in the UK and Dreissena polymorpha in the US. 10 marine molluscs
are listed by the Joint Nature Conservation Committee (JNCC) as non-native
to UK waters.
In
many ways the bias towards non-marine conservation and the debate about
species versus habitat conservation reflect what is going on in conservation
as a whole. But particular difficulties arise with molluscs. For marine
and freshwater species one is dealing with a mobile environment. The
fauna (perhaps the non-marine fauna in particular) is only well-known
in limited parts of the world - Europe, North America, New Zealand and,
possibly, Australia- so we do not know what there is to conserve. Degrees
of endemism and species' ranges vary; the ranges of non-marine mollusc
species in the tropics are often smaller than those of Holarctic species.
Island faunas often have a high degree of endemism, now usually impoverished.
One Pacific island has 100 endemic land snail species, some known only
from a single ridge or valley, and the "limestone islands" of the Malayan
peninsula hold several dozen species in areas less than 100 Ha. There
is clearly much surveying, ecology and taxonomy to be done so as to
focus conservation efforts to best effect. Rarity is a good indication
of which species are in danger of extinction, but Robert
Cameron warned that the impressive "species swarms" which are
a characteristic of many terrestrial mollusc faunas would fare less
well than species which are the only representative of a genus or family.
But the pace of events does not permit actions to proceed in series,
conservation measures need to be taken now in many cases.
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Examples
of conservation in action
Turning
to some of the cases we heard of, there was the narrow-ranged endemic,
Helix ceratina in Corsica which is not listed in any conservation
legislation and lives in a habitat which has no special protection either.
The conservation and status of Pearl Mussels, Margaritifera margaritifera
and the one population of M. auricularia received a good
deal of attention because of their decline in much of Europe and the
association with "treasure hunting". There have been enormous declines
in species richness in some freshwater habitats in the south eastern
United States. The problems for non-marine mollusc conservation in tropical
areas and islands, besides undescribed faunas, include unpredictable
effects of introduced predators or vegetation - for instance, Euglandina
has devastated defenceless Partula species, but has had less effect
on islands where molluscs have developed defences against indigenous
predators, and on Mauritius, exotic vegetation can shelter native species
so attempts to recreate "native" vegetation can be disastrous for the
molluscs. Further details are given below.
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The
"take-home" message
My
impression was that there is much that could be done to improve the
conservation of molluscs. However, to do this as a discrete activity
is not easy, especially because of the limited share of expenditure
and effort on conservation which conservation of molluscs can expect
to attract. More account needs to be taken of molluscs within general
conservation activities and we should emphasise the importance of molluscs
within the context of "wildlife conservation" at every opportunity.
By
the end of the conference it was clear that those attending felt that
it had been a success, particularly in developing international links
in this field, and that further similar meetings would be valuable.
One particular action was that many attendees were prepared to take
action in relation to the sale, by Sainsbury's Homebase chain in the
UK, of tropical shells, including land molluscs, as "renewable natural
products" (or words to that effect) - a problem drawn to our attention
by Sue Wells. As a result of this and action
by the Marine Conservation Society, Sainsburys, who appear not to have
been aware that the renewability claim might be incorrect, are reconsidering
their policy on whether to continue stocking this line of merchandise.
I,
and I am sure all other delegates, are very grateful to Mary
Seddon and Ian Killeen for organising
such a successful conference and to all those obvious enthusiasts who
so willingly took part in it. Can we have another soon?
David
Long
This
article is based on one which appeared in the March 1997 issue of The
Conchologists' Newsletter. It is intended to issue the Conference Proceedings
as a Conchological Society Special Publication in 1997.
The
Proceedings of the Alan Solem Memorial Symposium on the Biodiversity
and Conservation of the Mollusca, from the 11th International Malacological
Congress in Siena, Italy, 1992, edited by A.C. van Bruggen, S.M.Wells
and Th. C.M.Kemperman was published by Backhuys in 1995 (ISBN 90-73348-47-1)
Regular
information about molluscan conservation is contained in Tentacle, the
newsletter of the IUCN SSC Mollusc Specialist Group (No. 6 was issued
in September 1996). The editor of Tentacle is Dr R. Cowie, Bishop Museum,
P.O.Box 19000 Honolulu, Hawaii 96817-0916, USA.
Four
Case Studies from the Cardiff Conference
(a)
British Riverine Species
The
removal of Vertigo moulinsiana from the route of the proposed
Newbury Bypass was a feat of civil engineering. 600 square metres of
Glyceria turf 3-500 mm thick were moved, with the snails concentrated
in the moist leaf mat at the base. A millstream was then diverted through
the scrape with a 1 in 200 gradient. New growth was reported within
a month. However, V. moulinsiana has been added to 52 10K squares
since 1970 and will be in five SACs, so their Red Data book status seems
dubious. Translocation (this one cost around £0.25 million) should
not become a first option for the future. Pseudamnicola, a clean
river species, is a more worthy case for conservation, and could become
a flagship species.
Ian
Killeen suggested
that molluscs could be used as bioindicators for ditch management. Anisus
vorticulus, Segmentina nitidula, Vallonia maurostoma and Pisidium
pseudosphaerium flourish in late successional stages of ditches.
A Community Conservation Index (highest conservation score x average
score per taxon) of 10 would indicate little value, while one of 20
would indicate high value.
Some
species seem to defy attempts at conservation - Myxas glutinosa,
now Britain's rarest freshwater snail has a reputation for disappearing
from one site and turning up at another.
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(b)
North American Unionids
Art
Bogan drew
attention to the fate of N. American freshwater bivalve taxa: of 344
species, 35 are extinct, 49 endangered, 5 threatened in the U.S. and
61 are candidates for threatened or endangered category. Only 20% appear
to be maintaining their populations. The central problem is modification
and destruction of habitat, notably sedimentation, but damming has caused
the loss of obligate fish hosts of unionid glochidia larvae, and zebra
mussels (Dreissena polymorpha) introduced in the 80s have smothered
many populations of the native mussels. Conservation has had a positive
effect - 8 Unionids have returned to the upper Ohio River since the
1970 Clean Water Act, but Unionids have gained protection only by appeals
to the public conscience based on the value of the whole ecosystem.
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(c)
Pearl mussel
Margaritifera
margaritifera has become severely depleted in Britain by pearl fishing,
loss of salmonid hosts from acid rain, eutrophication and land drainage
(a site in Snowdonia was destroyed before piles of dead mussel shells
along the banks revealed its presence), and only one population, in
West Cumbria, is recruiting. Protection measures include provision of
good conditions for Sea Trout (the probable main vector), tree shade
to control algal growth, and regulation of cattle watering stretches.
In Finland, large populations persist but most are outside conservation
areas. A formula is used to set the level of fines for removal (£500
for a M. margaritifera, £6,000 for a Sea Eagle).Other methods
of conservation are stopping flow of silt into rivers from peatland
drainage, restoration of pool riffles, adding fish vectors, and restocking
- this is 90% successful between different stretches of the same river,
but only 50% successful from one river to another.
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(d)
Polynesian tree snails
30
taxa of Partula are now cared for in 17 different institutions
in Europe and N. America; most are now extinct in the wild as a direct
result of the introduced predator Euglandina rosea. Some species
in captive breeding programmes have been lost, but 20 species have been
saved from extinction. Viability was checked by releasing specimens
into Kew Gardens tropical house and monitoring their success: release
of 3 species in a 20 x 20 m predator exclusion zone on Moorea has started,
but Euglandina re-invaded when the electric fence broke down.
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