Ecological Basis for Restoration
The restoration of ancient ecosystems presents a huge challenge for nature conservation researchers and organisations.
One of the initial problems we face is not knowing the precise physical factors which made them work so well before they were disturbed.
In the case of wetlands this implies detailed research on the sediments and their dates, the soils, the geomorphological conditioning factors and original maps.
The main aim of our work so far has been to identify which particular factors are the most important ones in the possible recuperation of the wetlands of La Janda.
The Laguna de la Janda used to be one of the biggest and most important wetlands in the Iberian Peninsula. This is not only because of its intrinsic characteristics but also for its relation with the other wetlands in Northern Europe and Southern Spain as well as the pre- and postnuptial migrations of the majority of birds of the entire Palearctic ecozone.
It is located in the catchment area of the river Barbate in a tectonic depression in the province of Cadiz near the Atlantic coast of the southernmost part of Spain.
It was dried out at the end of the 1960’s, thus meeting the same fate as many other wetlands in Spain such as Antela in Orense and La Nava in Palencia.
In spite of the substantial drainage infrastructure put in place at the time, the occasional torrential downpours still cause floods which trace out the outlines of the ancient wetlands. These happenings open our eyes to the possibility of their partial recuperation in coexistence with agriculture.
One of the most interesting aspects of the research has come from studying the available records of the different phases of drainage. For example, there is precise data on the quantity and location of the aquatic vegetation which was mainly common club-rushes (Scirpus lacustris) and bayonet grass (Scirpus maritimus).
The mapping and its associated aerial photography done in 1956 and 1992 for the drainage allows us now to see the characteristics of the different wetlands as well their changes of use.
The La Janda wetlands were fed directly by the rivers Barbate and Almodovar. This vast area of marshes was made up of a mosaic of wet zones of which Rehuelga and Espartina lakes are remaining examples. Jandilla and El Torero lakes seemed to be formed simply also from this floodplain and Tapatanilla lake appears to be related to the Almodovar river. Its origin seems to be linked to a dissolving process of the underlying gypsum. This would explain the briny nature of the huge (3,700 hectare) marsh called "Charco de los Ansares" (geese´s puddle).
A series of modifications and actions has now been proposed for the whole area to re-establish its original condition; removal and diversion of canals and irrigation ditches, getting rid of canals and restoring old river courses, restoring dykes, preserving old community fisheries, etc.
In other areas such as the lakes in Alcala, La Haba and Cantarrana, limited amounts of conservation work should be enough to guarantee their health and natural functioning.
This initial study has definitely made a significant contribution to the knowledge of our wetlands in Spain and especially to our very few remaining wetlands on alluvial plains.
We hope it may allow us to reclaim a lost part of our national heritage.
Ecological Basis for Restoration of La Janda Wetlands (Cádiz, Spain)
PhD thesis Abstract
Author: Manuel Ángel Dueñas López
Director: Dr. José Manuel Recio Espejo
Cordoba University (Spain)