Old-Growth Forests
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Increase area of old-growth forest protected
Data collection in progress
Iberian Highlands
Spain
Problem: Timber extraction, together with resin production, is a major form of exploitation of the pine forests that dominate much of the Iberian Highlands landscape. In many areas, this has been led to the creation of a homogenous monoculture of Scots Pine trees, made up of young trees of the same age and size and a scarcity of areas of old-growth forests with specimens of different species and mixed stands. This has had negative effects on the biodiversity associated with old-growth forests.
Action: Rewilding Spain is working to develop agreements with landowners, often local municipalities, to protect and restore areas of old growth forest, allowing these forests to become more complex and diverse functional ecosystems. These agreements will be supported by models that provide financial compensation for carbon storage and changes to the timber market to reflect its true value.
Indicator: The number and area of old-growth forests protected by the project provides a direct assessment of the measures to protect these ecosystems.
Methods
The agreements signed with municipalities will provide information on each area of old-growth forest that is protected. GPS devices will be used to map the boundaries of each site and GIS software will be used to calculate the total area protected.
In addition, forest integrity and biodiversity in protected forests will also be measured. In July 2024, a baseline survey was conducted in the newly established forest reserve in Vega del Codorno.
For the baseline survey, 40 circular plots of 1 ha area each were established, comprising 15% of the total forest, shown in the map below (Fig. 1). The location of the plots was determined by first randomly selecting points from a grid, and then modifying some points due to their proximity to roads or other landscape features that would make them invalid. Surveying was conducted along parallel transects, and each plot was surveyed by a single observer. These plots will be revisited for future surveys.
Figure 1: Location of the circular survey plots (green circles) within the Vega del Codorno forest reserve area (blue).
To classify survey results from each plot, a method called the Potential Biodiversity Index (PBI) was applied, which was developed by the Centro de la Propiedad Forestal of Catalonia and and the French Centre National de la Proprieté Forestière. The PBI was applied at stand scale, following Baiges et al (2019). The PBI consists of ten key variables. For each variable, different states are defined on a scale from lowest to highest environmental integrity, with each state worth a certain number of points. The state of each variable is then assessed and the total number of points across all ten variables calculated. Specific guidelines for Spanish forests of the Mediterranean region describe how states are defined for each variable. For example, for the ‘native species’ variable, states are assigned depending on the number of native species present, with the lowest number of points for stands with no or only one native species, and the maximum points for stands containing five or more native species. Across all ten variables, the maximum number of points is 50 (max. 5 per variable).
In addition, percentage forest cover was recorded for each stand.
The baseline at the start of the project was 0 ha protected. In 2024, the first old-growth forest reserves in Vega del Codorno was created with an area of 261 ha.
For the baseline survey in Vega del Codorno, The mean PBI value, representing biodiversity and forest integrity, was 15.4 points ± 3.54 (s.d.) out of a possible 50, and the highest value for a single plot was 24. Mean forest cover was 45.1% ± 25.2 (s.d.).
The vast majority of stands were dominated by Scots pine (Pinus sylvestris) and black pine (Pinus nigra), with holly (Ilex aquifolium) and holm oak (Quercus ilex) present in some areas. Open spaces varied greatly, with some areas close to 100% open space and some densely forested areas with 0% open space.
Old-growth juniper tree in the Iberian Highlands. Photo: Rewilding Spain.
Interpretation
One of the main reasons for the low average PBI score of the plots is the relative immaturity of the forest. This is an area where wood has been extracted and the forest heavily managed for decades, and non-pine species are thought to have been actively removed since they were not of economic benefit. Despite this, there is high forest growth. Protecting the forest as a forest reserve will allow it to mature. It is expected that over time other non-pine forest species will begin to expand, generating a mixed forest with higher biodiversity. In addition, in the past deadwood was commonly collected due to the forest’s proximity to the town. With protection, the abundance of deadwood should also increase. These surveys will be repeated in future years to assess how forest biodiversity changes in the newly protected areas.
To assess temporal continuity, historical photographs were used to compare forest between 1956 and 2021. These photos revealed historical deforestation and more recent forest expansion. Some less exploited areas of the forest were also identified, corresponding with the areas where the largest trees were present.
References
Baiges, T., Cervera, T., Palero, N., Gonin, P., Larrieu, L. (2022). El Índice de Biodiversidad Potencial (IBP) como herramienta de apoyo a la gestión forestal: fundamentos y aplicaciones en Cataluña. 8º Congreso Forestal Español. Sociedad Española de Ciencias Forestales. ISBN 978-84-941695-6-4. 8CFE-646
Camprodon, J.; 2008. Elementos biológicos a tener en cuenta en la planificación forestal a escala de rodal y de paisaje. Cuadernos de la Sociedad Española de Ciencias Forestales, (27), 78-86
Europarc-España; 2020. Bosques maduros mediterráneos: características y criterios de gestión en áreas protegidas Ed. Fundación Fernando González Bernáldez, Madrid
Europarc-España; 2020. Bosques maduros mediterráneos: características y criterios de gestión en áreas protegidas Ed. Fundación Fernando González Bernáldez, Madrid.
Europarc-España; 2019. Manual de campo para la identificación de rodales maduros de referencia. Fase I: Prospección de rodales. Proyecto LIFE Redcapacita_2015. Deliverable B3.1. Ed. Fundación González Bernáldez. 29 p. Madrid
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