La Vall de Joan, a model of metropolitan ecological restoration

On December 4th, the conference on the restoration of the Vall de Joan took place at the AMB headquarters. A conference that took place after the guided tour that had taken place at the same landfill a few weeks earlier. The conference began with the welcome of Ramon M. Torra i Xicoy, manager of the AMB, followed by the intervention of Frederic Ximeno, who spoke to us about restorative metropolitan management, placing the Vall de Joan in the context of the Metropolitan Area of Barcelona and highlighting the importance of this pioneering macro-project of ecological restoration . From the first moment it was perceived that we were facing a project that places science at the service of territorial management , especially significant at a time when open spaces of meadows and grasslands have decreased significantly due to the evolution of the primary sector and that is deployed on the former controlled landfill of the Vall de Joan, the largest in the Barcelona conurbation.

The first presentation, by Ana Romero, from the AMB's Climate Action Services Department, allowed us to understand where we have come from and the magnitude of what has been achieved. Romero explained the origins and evolution of waste management in the metropolitan area and emphasized the territorial impact of uncontrolled dumping in the 20th century , recalling episodes such as spontaneous dumps in the final stretch of the Llobregat or in the Montjuïc quarries that had deeply marked the landscape and environmental health. She highlighted a key moment on May 3, 1974, when the 2,000 tons of daily waste from Barcelona began to be dumped in the Garraf , a decision that generated notable social mobilization and citizen opposition, who warned that the project was technically catastrophic for heritage and the natural environment. The tension between urban needs and the protection of the territory marked the following decades. Romero continued to explain how the access and management regime of the deposit changed over the years, until its final closure in 2006 , with a historical maximum of waste received in 1999. He concluded with a reflection by Ramon Folch that reminded us that the landscape is a socio-ecological system and that the restoration of the Vall de Joan is an exercise in shared responsibility and collective learning.

Then, Ramon Serrajordi, from the AMB's Waste Prevention and Management Services Directorate, immersed us in the technical challenges of closing and maintaining the landfill . He explained to us how impermeable clay was applied to the bottom of the deposit and how the slopes were sealed with gunite, bituminous emulsion, metal meshes and geotextiles, covering a total of 18 hectares, and how all this was done in several phases, starting with zones I and II between 2001 and 2003, the official closure in 2006, the lower zones III between 2008 and 2010 and the restoration of zones III and IV from 2019. Serrajordi stressed that today the Vall de Joan still presents complex internal conditions , with high temperatures, accumulation of leachates and gases and ground movements, and that constant environmental monitoring is required, including the protection of the Garraf karst aquifer and the use of numerical models to predict the future evolution of the risk.

Then, Andreu Salvat, from Aprèn and CREAF, focused his presentation on meadows and their function as drivers of biodiversity. He explained how, after the closure of the landfill, an open pasture space was generated that potentially becomes the most important part of the metropolitan area . In the context of the global biodiversity crisis, where meadows and grasslands are priority habitats for conservation and where a 34% decline in species in agricultural environments and meadows has been recorded, this project has a very clear meaning. For this reason, between 2023 and 2025, CREAF carried out a study of the vegetation of the Vall de Joan, analyzing the effects of grazing, defining potential vegetation and evaluating the distribution of exotic flora, as well as establishing conservation proposals for fauna, especially herpetological . Andreu explained to us that, while the sectors restored more than twenty years ago present a high level of naturalization and a mosaic of habitats with woodlands, scrub, greens and grasslands, the richness of herbaceous species is low and the evolution towards mature meadows is very slow, especially due to the absence of large herbivores, which leads to closure and loss of biodiversity. Thus, a grazing management with sheep is proposed that maximizes the benefits for biodiversity.

Brenda Saavedra, also from the AMB's Climate Action Services Directorate, completed the ecological perspective by highlighting the emerging values of what she calls a techno-ecosystem. She spoke to us about the global context of the biodiversity crisis and the need for scientifically based actions. The restoration of the Vall de Joan must serve as a reference model, especially in the meadow area, with bases for amphibians and ecosystem monitoring of various environmental vectors such as sun, water, air and diversity . The monitoring results show that there are currently more than 60 species of birds between nesting and visitors, including high-priority species from the Garraf Natural Park, and that 88% of the vegetation species are native .
The architectural presentation by Batlle i Roig Arquitectes allowed us to understand how the restoration was approached from a landscape point of view. The team studied the historical evolution of the landfill and was inspired by traditional agricultural systems, such as terraces and terraces , to design the ridges and slopes that allow controlling the dynamics of the water and integrating the project within the Garraf Natural Park , taking into account the protection of the Bonelli's eagle and the rest of the existing fauna.

Finally, Laia Batalla and Pere Artigas, from the Escola de Pastors i Pastores de Catalunya, explained how extensive grazing is a tool to maintain the balance of meadows and preserve biodiversity . They detailed the proposal for a silvopastoral system in the Vall de Joan, where they have proposed a management with high loads and short times of 300 sheep for 73 days and the use of sectorizations and mobile water points to maintain herbaceous vegetation and protect nesting birds. Grazing has shown in other places to have a positive effect on conservation value and helps to avoid bush encroachment and the spread of fires.

The day closed with Joan Pino recalling that this restoration project is the most ambitious carried out to date in Catalonia . The Vall de Joan has become a techno-ecosystem with multiple natural values and must serve as a reference for future projects, recognizing the errors of the past and highlighting the will to correct them through an extreme and coordinated restoration that combines science, technique and management of the territory.