Chapter Twenty

Plants -  The Roselières

Les Roselières - The reed-beds

This section is based on 25 years of SILA [p 39] by Jean-Pierre Courtin, and an exhibition of photos and interviews by students  studying for a certificate in ‘Nature management and protection of nature’ of ISETA, organized by Damien Zanella

Before considering the destruction of the reed beds begun during the last century and continuing to this day, we should recall their 8 key roles in the life of the lake.

1. First and foremost is the role of calming the lake. The cordon of reeds around the lake acts like a sponge soaking up the incoming waves and releasing them gently back to smooth the surface of the lake.

2. Then there is mechanical purification. The reeds act like a comb picking up material in suspension in the water and depositing it on the lake floor.

3. And chemical purification. The reeds absorb the very same fertilisers which cause the problem of eutrophication. In fact they are the biggest consumers of nitrogen and phosphorus among the whole range of aquatic plants!

4. And not least, bacteriological purification. The intensity of life within the reeds causes the growth and destruction of disease carrying germs. The reeds’ roots emit bactericidal substances which kill these germs.

The construction of the sewer pipe around the lake in no way renders obsolete the reeds’ purifying role, especially where tributaries enter the lake. INRA studies show that the lake continues to receive high levels of phosphorus, perhaps even exceeding the lake’s powers of self-cleaning.

5. The reed beds are also a safe habitat for several important species of fish – such as brochets, carpes, bremes, perches, gardons.

6. They are also a nesting ground for many varieties of birds, especially the grebes and foulques. The marshland of Saint-Jorioz is the only place in the whole of Haute Savoie where the purple heron makes its nest.

7. The reed beds are also an important place for hibernation for several birds including ducks and Sarcelles and an indispensible staging post for their migration.

8. And last, but no means least,  the reeds are a beautiful sight for visitors and locals to gaze on, an element of diversity adding variety to the shore line.

The destruction

“The area covered by the reed-beds has been reduced by 50 to 75% on the lakes since the start of the 20th century." - Coastline and Lakeshore Conservation Trust.  This destruction has two causes. The most obvious is the one-off destruction by local people to build houses, pontoons, moorings, beaches etc and in other ways to get access to the lake.  But there is a second, more insidious, long-term destruction caused by the fact that the lake’s water level is artificially kept the same throughout the year. In 1965 great sluice gates were installed on the river Thiou in Annecy to regulate the water level for the convenience of those living around the lake. But what is a convenience for them is slow physical torture for the reeds, because the impact from waves strikes repeatedly at the same part of the reed stem. It is especially punishing during the summer when there are many watersports on the lake.  The constant attrition weakens the stem until it breaks. Once broken,  water enters the stem and rots it down to the roots. The resulting contamination extends progressively through the root system, creating a dead zone, a weak point which in turn exposes neighbouring reeds to further attrition and so accelerates the recession of the reed beds around the lake.

In fact a fluctuation in water level throughout the year of just 60 cm (30cm up and 30cm down) would be enough to prevent this destruction. But that would be inconvenient for some people, and so the destruction of this key contributor to the health of the lake continues unabated.

What is being done and what more can be done?  In 2012, SILA, in partnership with ISETA (Institute for the Environmental Sciences and the Annecy region), embarked on an ambitious programme to restore the aquatic reed-beds on Lake Annecy.  “We’re thinking of broadening the APPB (Prefectoral Order for the Protection of the Biotope) and/or the Nature Reserve to include the aquatic reed-beds.” ASTERS Haute Savoie NaturalAreas Conservation Trust.

“We need to find a fair balance between the activities that take place on the lake and the protection of biodiversity.”  - Coastline and Lakeshore Conservation Trust.

“We are only repairing what we have destroyed.” - Mayor of a lakeside commune.

“The challenge now is to trust in people’s sense of civic duty to preserve the aquatic reed-beds on the shore side.” - Mayor of a lakeside commune

Continue Reading   Chapter Twenty-One