The Mediterranean climate is quickly changing, with more prolonged and severe droughts, less water availability and more frequent extreme events such as fires. In addition, this region is suffering from rural depopulation, which has caused the disappearance of small areas of crops and pastures, now populated by forests. In this context, the ECOFARMERS project, coordinated by Xavier Domene, CREAF researcher and professor at the Universitat Autònoma de Barcelona and Jordi Sierra, researcher at the Universitat de Barcelona, is assessing various techniques and cutting-edge products to adapt agricultural and forestry management activities to this new situation.

In particular, the project compares agroforestry plots that conventionally manage the land with areas that apply more innovative formulas and that are focused on regenerating soil. The reason is that "fertile and healthy soil can store more carbon, retain more water, host more biodiversity and increase agricultural or forestry productivity. All of this contributes to increasing climate resilience," explains Domene. Among the plots selected as innovative are those that use fertilisers made from organic waste and others that have reduced tillage or carry out vegetation thinning in forests. To carry out the experiments, the research team has settled up seven scenarios in various locations in Catalonia: four agricultural, two forestry and one on the site of an abandoned mine. The benefits and risks of each 'recipe' are measured based on five ecosystem services. Thus, the researchers calculate whether the practices are helping to sequester carbon in the soil, produce more food, reduce greenhouse gas emissions, maintain nutrients in the ground and increase biodiversity.

"One of the most relevant things about the project is that these are long-term experiments. We evaluate the plots in a range from 7 years to 100 years, depending on the plot. This ensures that the results we observe are reliable".

XAVIER DOMENE, CREAF researcher and one of the project coordinators.

The results will help farmers and forest owners to choose management models that, in addition to producing food and wood, improve the ecosystem services of crops and forests.

ECOFARMERS began in 2021 and is coordinated by CREAF and the University of Barcelona. The Spanish Ministry of Science and Innovation funds it and counts on the participation of several research centres such as the University of Girona, the University of Antwerp and the Senckenberg Gesellschaft für Naturforschung. IRTA, the University of Lleida and the CTFC are also collaborating and have lent some of their experimental plots to the project.

'Recipes' for improving agricultural and forestry management

The aim is to help farmers and forest owners choose management models that, in addition to producing food and wood, improve the ecosystem services of crops and forests.

In the case of agricultural fields, the team is assessing the beneficial effects of using fertilisers based on biochar, a charcoal that delays the release of nutrients to the soil, and those based on struvite, a by-product of sewage treatment plants or slurry. Another thing the team studies is the effects of reducing tillage and crop rotations, which, according to Domene, "contribute strongly to increasing carbon sequestration, preserving soil structure, reducing erosion and making better use of water in periods of drought".

The researchers also assess the impact of rural depopulation. In particular, they observe how soil microorganisms and fauna communities, vegetation and carbon stocks have changed. Moreover, they also test some measures to improve forest management. One example is forest thinning in areas with many shrubs and trees. According to Domene, this action can reduce the competition of vegetation for water and, therefore, contributes to maintaining production during periods of drought. However, the team warns that it could also negatively affect other services, such as soil's biodiversity, "we are precisely investigating this benefit-risk balance".

Mine restoration

Another of the scenarios they have set is the rehabilitation of soils degraded by open-pit mining, intending to restore them as forests. Specifically, they are investigating the use of  the use of techosols or contructed soils on demand. These technosoils can be created using organic materials that could improve the soil's health; they are known as organic amendments. For example, sewage sludge can be used as an amendment, "it has been shown that sludge favours carbon sequestration and the amount of nutrients in the topsoil," says Domene. But it can also have negative effects, as it contains heavy metals and microplastics that could be accumulated in the soil and contaminate it.

"With the results, we want to improve decision-making in agricultural, forestry and soil restoration policies in various contexts," Domene concludes.