CASE STUDY 2. SUSTAINABLE AQUACULTURE FOR THE ECOLOGICAL AND ECONOMIC IMPROVEMENT OF MEDITERRANEAN COASTAL WETLANDS: THE CASE OF DONANA (SW SPAIN)

D. Cebrian, M. Medialdea
UNEP-MAP RAC/SPA

 

Introduction

The International Union for Conservation of Nature (IUCN), through its Marine Programme, and the Federation of European Aquaculture Producers (FEAP) signed in 2005 a common agreement to cooperate in the development of sustainable aquaculture, promoting best practices in the sector. In addition, GFCM and its subsidiary CAQ have agreed on the importance of identifying positive interactions between aquaculture/fishing practices and coastal biodiversity conservation along the Mediterranean Region, taking into account the existing successful initiatives.
In Mediterranean countries where extensive/semi-extensive aquaculture and traditional fishery systems are still practiced, managed wetlands and lagoons constitute habitats for numerous threatened species of fish, amphibians, reptiles and birds. These activities effectively contribute to both the environmental conservation and the development of local economies, and could provide a sustainable future for the coastal wetlands of the entire Mediterranean Region. This is the case of Veta la Palma farm, an extensive aquaculture operation located in the Donana wetland, Southern Spain, where economic benefits result from the application of innovative production methods involving a wide environmental concern. This fish farm has not only been managed to supply top-quality aquaculture products, but also to minimize its ecological footprint and enhance natural ecology and biodiversity of a formerly degraded wetland area. Veta la Palma has become internationally recognized for its role in conservation and was awarded in 2003 by the Anders Wall Foundation in cooperation with the Directorate-General for the Environment of the EC (Otero and Bailey, 2003).

This document presents the activity of the Veta la Palma fish farm as a good practice in the management of lagoons. The document is part of a longer work prepared for the Regional Activity Centre for Specially Protected Areas (RAC/SPA) of the UNEP Mediterranean Action Plan, in the framework of a regional project currently under elaboration, which aims at promoting the use of sustainable aquaculture/capture fishery as a base for wetland conservation and management, within the Strategic Action Programme for the Conservation of Biological Diversity (SAP BIO) in the Mediterranean region (UNEP-MAP-RAC/SPA, 2003).

Veta la Palma: brief overview of its natural history

Donana has been designated a Wetland of International Importance under the Ramsar Convention and a Biosphere Reserve under the Unesco Man and Biosphere Programme. The area currently devoted to aquaculture in the area extends over 3 200 ha in the privately ruled Veta la Palma estate, occupying the formerly degraded Isla Mayor del Guadalquivir.
Donana climate is Mediterranean, moderated by the ocean, with warm dry summers and cool wet winters. The mean annual temperature is 17?C, while average annual precipitation reaches 525 mm (Llamas, 1988). Geographically, Isla Mayor lies at the centre of the Guadalquivir river delta, and is bound on the east by this river and on the west by Donana National Park.
After a long history of natural evolution by silting-up (Bayan Jardin, 2006), first attempts to transform Isla Mayor into farmland date back to the nineteenth century. In 1923, major channelling works were undertaken to prevent annual flooding, in order to transform the area for cereal agriculture. Rice was introduced as an alternative crop for the poor soils of the marshes in 1937. In the 1940s and 1950s of the twentieth century, rice culture became the main activity in the Guadalquivir river marshes, including the North of Isla Mayor. In 1966, 11 300 ha of the Southern Isla Mayor (the present Veta la Palma estate) were sold to the company Agropecuaria del Guadalquivir, which improved the flood defenses and used this traditionally grazing land for cattle breeding. In 1978, part of the estate (approximately 8 000 ha) was declared a protected area by National Administration. In 1982, Agropecuaria del Guadalquivir was bought by Hisparroz, S.A. and renamed as Pesquerias Isla Mayor, S.A. (PIMSA), which is the present owner of Veta la Palma estate. The former drainage network was improved and used in a reverse way, that is as irrigation canals, to create shallow lagoons for aquaculture purposes.
Considering the favorable results obtained in some preliminary experiences undertaken between 1982 and 1984 (Garcia Novo, 1988), in 1990 PIMSA decided to initiate an ambitious aquaculture project in Veta la Palma, under approval by local Fishing Administrators, according to the Plan for the Use and Management of Donana National Park (PRUG) regulations; 3 200 ha of the estate were flooded with first-rate water from the Guadalquivir river delta. The result was a carefully managed wetland supporting a rich and nourished flora and fauna, particularly dense communities of invertebrate species, which are the basis for a vast range of extensive aquaculture products. Farmed species are typical of the delta, including European seabass (Dicentrarchus labrax), gilthead seabream (Sparus aurata), meagre (Argyrosomus regius), soles (Solea solea, S. senegalensis), white shrimp (Palaemonetes varians), eel (Anguilla anguilla) and grey mullets (flat head grey mullet Mugil cephalus and thin-lipped grey mullet Liza ramada). Some 4 600 ha of Veta la Palma extension is marshland pasture for extensive livestock, producing horses and livestock; on the remaining 3 500 ha rice and dry cereal are grown on a rotational basis.

An innovative land-based aquaculture system

The Veta la Palma fish farming area is divided into 45 rectangular, 70 ha ponds, connected to each other and with the Guadalquivir and Brazo de la Torre rivers by means of a complex 300 km irrigation and drainage canal network. To maintain oxygenation and water quality, one million cubic meters of water are pumped daily from the river delta through the whole system, which is designed to work both in open and close circuit, depending on environmental and operational circumstances (Fig. 1).

Satellite image of Veta la Palma estate (centre).
Images illustrate current activities, photos ©Veta la Palma, H. Muniz, A. Liebana and J. Ramos.

Pumping station
Extensive ponds
Irrigation and drainage channel network

Semi-extensive culture units
Tidal flood-gate

Figure 1. Operational scheme of Veta la Palma fish farm (Source: PIMSA, 2000)
Extensive fish farming ponds are characterized by their stability regarding flooded surface (3 200 ha), average depth (40-50 cm), water flow rate (up to 1 hm3/day in summer) and salinity, although salt content may fluctuate according to the season and the amount of rain (6-15 g/l in wet periods and 15-25 g/l during driest episodes). This stability allows to buffer changes in the salinity, water flow and nutrient concentration values of the Guadalquivir delta, promoting a massive development of microalgae that efficiently assimilates excess of organic matter in the water, particularly nitrogen and phosphorus produced as waste, avoiding harmful algal blooms (PIMSA, 1995). Microalgae, as well as sediment-linked algae and bacteria taking part in decomposition, are predated by a varied aquatic microfauna composed of worms, insects, crustaceans and small fishes that ultimately constitutes the natural diet of cultured fish (Medialdea, 2009).
Extensive ponds act like huge water treatment plants where potential contamination of biological origin is removed from the water and transformed into living biomass that is finally extracted from the system via commercial fishing and predation by birds. Thus, the hydrologic system operating in Veta la Palma avoids eutrophication and assures that the water pumped daily from the Guadalquivir is returned to the delta with an improved microbiological, physical and chemical quality (Medialdea, 2009).

Aquaculture as a base for a sustainable wetland management

Restoration of lost ecosystem functionality

Veta la Palma aquaculture ponds and surrounding marshland pastures effectively support a number of environmental services for the hydrology and ecology of the Donana wetland. The aquaculture operation has been managed to restore the damage produced in the original wetland by silting-up and land misuses, minimizing its own ecological footprint and combining the economic benefits of aquaculture with conservation objectives.
The ecological and functional mosaic created in the Veta la Palma estate by PIMSA, inundating the formerly dried up marshland for aquaculture and preserving the surrounding high-marsh areas for extensive livestock grazing, has improved the natural landscape of the area. Since 1990, the estate?s ownership has also invested important material and human resources to further improve Veta la Palma’s ecology, through initiatives involving the construction of more than a 100 islands inside the fish farming ponds to serve as bird sanctuaries and nesting sites for waterfowls (PIMSA, 2000); total re-vegetation of 150 km of pond shores and embankments; and creation of two 300 ha and 500 ha Bird Protection Areas, including shallow lagoons with islands and areas with different ecological types of marshland (PIMSA, IIMA and Euroduck, 1992), for research purposes. Islands are composed mainly of slime and clay coming from the Guadalquivir estuary, which contain plant seeds and can be used as substrate for revegetation. In just a short time, new islands get covered by a rich carpet of halophytes and marshland shrubs, offering a new and heterogeneous habitat to aquatic birds.
The Donana wetland exhibits a hydrologic regime that includes a high water table and extensive flooding from October to May-June, followed by a strong summer drying. Every year at the beginning of the summer season, thousands of waterfowl and coot broods leave Donana and seek for flooded areas in surrounding sites, massively arriving to Veta la Palma. Similarly, at the end of summer and the beginning of fall, the marshes of Donana National Park are still dry, and the clean, oxygenated and food rich water of Veta la Palma offers shelter for thousands of early migratory birds. Therefore, the Veta la Palma aquaculture operation plays a fundamental role as buffer zone for the whole area and provides food and water for the birds during moulting time, breeding season and post-breeding annual migration, as well as during particularly dry interannual periods (Quiros Herruzo and Maneiro Marquez, 1996; EBD, 2000).
Wintering ground for visiting northern birds (e.g. 70 000 greylag geese) and nesting sanctuary for spring-migrating species from Africa (e.g. 500 purple herons), Veta la Palma has become the lungs, larder and hospital for European aquatic birds. From some 30 000 birds recorded in 1984 (Fernandez-Cruz et al., 1989), the population has exponentially increased to a total of 600 000 in fall months (Fig. 2), attracted by the abundance of fish and shrimps (Rodriguez Perez and Green, 2003). More than 250 species of birds can currently be recorded in Veta la Palma, almost 50 of them included in the IUCN Red List of Threatened Species (IUCN, 2011). Kentish plover (Charadrius alexandrinus), slender-billed gull (Larus geneii), osprey (Pandion haliaetus), greater flamingo (Phoenicopterus ruber), little tern (Sterna albifrons) and gull-billed tern (Sterna nilotica) are also included as threatened species in Annex II of the Protocol concerning SPAs and Biological Diversity (SPA/BD) of the Barcelona Convention. The total bird population size reaches the maximum between August and October. Census data by the Donana Biological Station recorded a total of 600 000 birds in Veta la Palma in October 2002, which represented 80 percent of all birds of Donana by that time (EBD, 2000; 2004). The estate is currently regarded as the most important area of private land for aquatic birds throughout Europe (Otero AND Bailey, 2003).

Figure 2. Evolution of the population of some relevant species of birds in the aquaculture ponds of Veta la Palma, for the period 1973–2001 (marshes still dried for cattle grazing, before aquaculture project started) (Source: PIMSA, 2000; EBD, 2004)
The first-rate water layer dedicated to extensive/semi-extensive aquaculture in Donana also contributes to the protection and eventual recovering of the Guadalquivir delta-associated fish fauna (Table I). The highly structured trophic web of Veta la Palma fish ponds plays an important role in the protection of relevant species as the Spanish toohcarp Aphanius iberus (included in Annex II of the Protocol concerning SPAs and Biological Diversity – SPA/BD – of the Barcelona Convention), Allis shad, Alosa alosa and twaite shad, Alosa fallax (included in the Annex III of the Barcelona Convention), sand goby Pomatoschistus microps, big-scaled sand smelt Atherina boyeri, and other species that spend part of their natural cycle in the delta (spotted seabass
Dicentrarchus punctatus or the farmed soles, seabream, meagre, eel and seabass). Some marine species, such as the European anchovy Engraulis encrasicholus, the wedge sole Dicologoglossa cuneata or the sand steenbras Lithognathus mormyrus have also been recorded during dry periods, when water salt content increases. Apart from juveniles of cultured species which are bought in commercial hatcheries and released in the ponds, larval stages and juveniles of most mentioned fish species are usually found in Veta la Palma.

Contribution to climate change mitigation

The Donana wetland is located in a crucial point in terms of exposure to climate change, with desertification, erosion and sea level rise as major forces that may affect both the biodiversity and the economy of the local community. All climate changes scenarios in the area indicate marked increases in temperatures and a significant decrease in annual rainfall (Viner and Sayer, 2006) that will surely affect soil salinity, making agriculture even harder on this region of Spain.
Under these changing conditions, aquaculture may become a serious alternative to ensure future water availability and control for the entire wetland ecosystem. Extensive/semi-extensive aquaculture in Veta la Palma is based on a complex system of canals that allows to regulate the water across the Estate and surrounding areas, taking into consideration both productivity and biodiversity. The 300 km of channels of Veta la Palma, the rivers bordering the estate where fish farming develops, and the huge patch of protected lagoons and marshland pastures surrounding the extensive fish ponds allow the whole Donana ecosystem to mitigate the effect of a decrease in precipitation by adapting the water control scheme and pumping operation from the river delta. Water, salt, food and vegetation cover combine themselves to provide excellent opportunities for animal breeding and feeding, transforming this area in an oasis for many species that have to face changes in climate and habitats occurring in both Europe and Africa. Regarding carbon balance, growing emissions from livestock and rice (76 percent of all emissions; Viner and Sayer, 2006) in the area may be compensated by carbon sequestration through photosynthesis in the aquaculture operation.
Conclusion: Eco-friendly aquaculture may guarantee the protection of Mediterranean coastal wetlands, promoting the balance between biodiversity conservation and development
The sustainable aquaculture system currently operating in Donana is a highly successful model of integrated management in an extremely sensitive Mediterranean coastal wetland (Abend, 2009). The areas of extensive aquaculture ponds, natural marshlands and cereal farming constitute an ecosystem of great wealth, where balanced human management has recovered a former wetland that had been largely disturbed, increasing natural gradients of hydrographic and topographic heterogeneity (Ecoagriculture Snapshot, 2010). Fish farming activities maintain the Guadalquivir river delta in a favourable conservation state and become a very valuable support for Donana, representing a compromise with the future of conservation and development in the area (Otero & Bailey, 2003).
The Veta la Palma aquaculture operation in the heart of Donana has the recognition and support of a number of international institutions such as WWF, the Royal Society for the Protection of Birds and Wildlife Trust, Euroduck Internacional, the European Landowners Organization, the Spanish MAB (Man and Biosphere) Committee (Unesco) and the European Commission. In addition, the production methodologies applied in the farm are included in what the Directorate-General for Fisheries and Maritime Affairs, European Commission, called aqua environmental measures. As defined in the European Fisheries Fund (EFF), aqua-environmental measures aim to promote aquaculture techniques that help to protect and improve the environment and to conserve nature (EU, 2007). Such technologies have to be ecologically efficient and respectful, under hard environmental exigencies within the framework of Natura 2000.
This model of eco-friendly aquaculture constitutes an interesting and efficient case study in relation to the modern safekeeping of the territory, in which collaboration between private and public initiatives based on investment in eco-friendly productivity solutions makes an enormous contribution to the conservation of coastal wetland natural resources, generating both economic
and ecological outcomes (Cranbrook, 2002; Dura and Castroviejo, 2007).
Table I. Vertebrate species recorded in Donana aquaculture operation, considered under threat according to IUCN List of Threatened Species (Source: IUCN, 2011)

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