Rewilding in the areas surrounding Portugal’s Sabor river
Situated between the north-eastern municipalities of Torre de Moncorvo and Alfândega da Fé is Portugal’s Sabor river. Now the home of the Barragem do Baixo Sabor – a 123 metre high hydropower plant - the 150,000 hectare wildE case study area has been subject to varying land use dynamics over the last century.
The contemporary landscape of the Sabor river
As the land experienced a transition to mass cultivation due to state campaigns to encourage food self-sufficiency in the 1930s, and the later abandonment of these policies, the ecosystems in the area, studied by BIOPOLIS CIBIO, began a natural process of rewilding.
Wheat cultivation, land abandonment and ecosystem restoration
Following its establishment in 1933, the Estado Novo regime placed great emphasis on food self-sufficiency, as a consequence of the economic, social and political environment created in Europe in the aftermath of the 1914-18 war. To achieve this, numerous subsidies were provided to encourage mass cultivation across the country, particularly of cereals.
The area surrounding the Sabor river was one of various regions which experienced significant environmental changes as a result of these state policies. To make way for a more intensive approach to farming, nearly all vegetation and scrubland were cleared, leaving only small patches of the land’s natural ecosystems remaining. These small patches of woodland scattered across the landscape, mainly oak and maritime pine, were preserved because of their importance as a source of firewood for domestic fuel. This was the first significant environmental change during the time period of the case study’s research, causing the land to look considerably more homogeneous than before.
Farmers harvesting and gathering cereals
Ox-drawn carts transporting the harvested cereals
This took place, however, on all available land, regardless of its suitability for cereal crops. Most soils were not of sufficient natural quality to support the crops' intensive rotation without fallow periods, and adequate fertilization wasn’t available. Towards the end of the 1940s, farming at this scale became unsustainable, erosion increased and soils became exhausted and depleted, causing production to rapidly decline.
As the land was no longer providing economically for the local communities, there was increasing emigration of the local population to neighbouring countries and urban areas, with an average 45% population loss in the region up to the 2010s. Those who remained in the area mainly transitioned to cultivating permanent crops that require less hard labour, such as almond and olive trees. This mass abandonment of the land caused the second considerable environmental change in the area, and a natural process of rewilding slowly began.
The third change occurred following the construction of the Barragem do Baixo Sabor in 2008. Despite the environmental implications usually associated with large hydropower plants, it is this event which makes the area of particular interest for the wildE project’s research. In order to be approved, the project was subject to strict environmental compensation measures which means that, in addition to the natural processes of restoration that have occurred in the area and many others across Portugal, the land has also experienced interventions, directed management and protection which have impacted its restoration.
wildE’s research around the Sabor river
These changes in land use over the last century make an interesting case for rewilding in Europe. Currently, wildE’s research in the area centres around estimating the speed of recovery of vegetation from the moment it was abandoned to the moment the forests are restored.
Using aerial photographs from the 1940s to the 2010s, the wildE team have been able to analyse plots of land which were abandoned at different points during this period to understand how vegetation has changed and recovered over time, and how long this process of restoration may take.
From this analysis, they have found that forests and more developed vegetation can take around 60 to 80 years, or even longer, to restore. This is because the intensive nature of cultivation in the 1930s and 40s caused high levels of soil degradation and, because forest clearance, limited the sources and dispersal opportunities of seeds.
The team then considered what nature was actually restoring to, and whether this meant it returning to its original state. Due to the construction of the dam, there was a vast amount of research conducted on how the land has been managed throughout history. Using the archaeological data produced in this investigation, it was discovered that the land had been inhabited for at least 30,000 years. Because of this, there have been huge changes in vegetation, meaning that in this area there is no benchmark for “naturalness” as humans have been using and managing the land in different ways for millennia.
Thus, rewilding in this case does not involve nature restoring itself to how it was in the past, but rather it is converging to a new situation, which will depend on how we manage the land and what we want for the landscape.
What does the Sabor case study mean for climate-smart rewilding?
Despite the rewilding process being slow, the area has already started to see some results of the renaturalisation process. Some oak forests have reemerged since the land was abandoned, there have been increases in several species of animals, such as large birds of prey, roe deer and wolves.
The contemporary landscape of the Baixo Sabor region
Although rewilding is a wide-spread concept, when it is put into operation, each situation is unique to the context of the specific region. The research carried out in the Sabor case study area will demonstrate what rewilding could look like in regions where there is a long history of human occupation and where there is no clear natural benchmark.
Furthermore, only a small portion of the land is protected by the electrical company that operates the dam, and so a lot of these processes of renaturalisation are occurring on private land via agreements with landowners. By constructing different scenarios and pathways for the landscape, the case study hopes to provide the local people - who often perceive the restoration negatively, as they find land cultivation more beneficial - the clear advantages of the rewilding process. This way, the wildE project will be able to set guidelines to improve carbon sequestration in the area by recovering natural vegetation, controlling and reducing fire risk, and creating social and economic benefits for communities.