Saône-et-Loire Sand Dunes Border a Sundew Bog with a Landscape Younger Than It Appears

Near the confluence of the Saône and the Seille, a state-protected nature reserve brings together sandy stretches, a peat bog and a pond. These “dunes” intrigue, far from any shore. On-site studies show that wind, the river, and humans have shaped them, alongside carnivorous plants nestled in the sphagnum.

Created by the decree of December 3, 1980, the reserve officially covers 93.04 hectares in the heart of Bresse

The idea of protecting this area arose as early as 1970, to prevent sand and peat extraction as well as urbanization. Subsequently, decree no. 80-993 of December 3, 1980 established protection spanning La Truchère and Ratenelle. A second decree, dated August 24, 2005, amended this text.

According to the National Inventory of Natural Heritage, the official surface reaches 93.04 hectares, classified as IV by the IUCN. Since 1990, the Bourgogne Natural Areas Conservatory has managed the site. Thus, its fourth management plan, drawn up for 2016–2025, outlines scientific monitoring and works.

Fluvial sands moved by the wind since the Mesolithic have shaped these continental dunes

The management plan relies in particular on a 2012 study by Steinmann and colleagues. Using ground-penetrating radar, a non-destructive method, the team analyzed the internal structure of the mounds. Moreover, the appearance of the sand grains confirms windborne transport of materials originally supplied by the rivers.

This movement would have begun in the Mesolithic, then intensified between the 5th and 15th centuries. The authors link this phase to the deforestation of ancient sandy terraces dating from 3.4 to 2.6 million years ago. Furthermore, the Conservatory notes that the sandy expanses and the peat bog formed more than 10,000 years ago.

However, the visible relief today would be younger. The horizontal sand layers are cut across by the present surface, a sign of erosion after the end of the Middle Ages. From then on, floods of the Saône or Seille, or ancient extractions, could explain these shapes.

In the Lioche bog, sphagnum moss hosts the round-leaved sundew and its intermediate cousin

Just a few steps from the dry sand, the woody bog of the Lioche provides a waterlogged and acidic environment. The mats of sphagnum retain moisture permanently. This type of habitat is more often found in mountains or in cooler climates than on the plain of the Saône.

Two species of sundews are recorded there. The round-leaved sundew grows in the bog, while the intermediate sundew develops in the damp areas near the sands. Their leaves covered with sticky hairs trap tiny insects, supplying valuable nitrogen in a poor soil.

Meanwhile, the Fouget pond, about 5.7 hectares in area, completes this mosaic of wetlands.

Without grazing or regular works, the sandy lawns would retreat in favor of heathlands and then forest

Left on their own, the sandy areas gradually close in. The pioneer grasslands give way to heathlands, then to woodlands. Therefore, the manager intervenes to preserve these clearings.

The Conservatory has scheduled operations of harrowing, cutting, and uprooting trees. Additionally, herds have returned to the site for routine maintenance. An educational trail guides visitors between sand and peat.

These dunes thus illustrate a common paradox in conservation. To preserve a landscape born in part by human activity, the reserve must artificially maintain a habitat that nature would otherwise cover with forest.