Mesleard article

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Converting abandoned rice fields to rangeland in the Rhône delta

François Mesléard

The Camargue, like a great number of the Mediterranean wetlands, has suffered for the last 50 years from the loss of natural habitats. The expansion of rice cultivation in the Rhône delta after the World War II led to the disappearance of large areas of natural habitats, most of which had previously been used as rangelands. During the same period, the number of horses and cattle increased, resulting in an approximately 2-fold decrease in area available per head. In the 1970s, a fall in the price of rice led to the abandonment of the less productive land, most of which was seasonally-flooded brackish or saltwater marshes.

Because of high soil salinity, summer drought and the disruption of landscape features required for rice cultivation, the restoration of the important biological functions that existed prior to cultivation, as primary production and wildlife habitat, is impossible without management. In this perspective, an experiment was initiated aiming at measuring the effects of artificial flooding on vegetation dynamics, and the benefits of management for both wildlife and domestic stock.

Six management regimes (two artificially flooded for 6 months and a control irregularly flooded by rain, with or without grazing) were tested in 18, 1-ha plots from 1 November 1989 onwards. These fields formed part of a 250 ha of abandoned rice fields uncultivated since 1976.

The results of the experiment showed that the management regimes for abandoned rice fields seem favourable for both conservation of wildlife and for improvement in pasture quality.

Artificial flooding led to an approximately 10-fold increase in the overall total production on the abandoned agricultural land. It also resulted in considerable increases in the crude protein, Ca, and P concentrations in the spring and summer.

From a pastoral viewpoint, seasonally-flooded abandoned rice fields therefore play a similar role to that of shallow marshes. In the autumn, rice fields, like marshes, only play a marginal role, they fulfil a similar function to that of non-flooded grasslands on the higher ground. From the wildlife conservation viewpoint, the results showed that abandoned rice fields can be managed for waterfowl, and that flooding, in combination with grazing, allowed the creation of habitats differing in their height and species composition.

Beyond protected areas, such type of management could be particularly adapted to low-lying land with poor productivity. They could then play a role as buffer zones situated between reserves and intensive agriculture, where conservation (habitats for wildlife) and agriculture (livestock production) could cohabit. This principal could be applied to numerous Mediterranean coastal sites, where intensive culture is unprofitable.