Despite this increase in surface area, only 9% of all forests have a certain degree of maturity and most are still young, dense and often structurally very homogeneous and, therefore, more vulnerable to the effects of climate change.
Mountain pine has deep roots in the Pyrenees, but climate change threatens its future
Since 1956, the area covered by these forests has increased by nearly 30%. However, most of them are still young, which limits their ability to withstand droughts, wildfires, and other impacts of climate change.
The habitat of Scots pine forests (Pinus uncinata) is protected by the European Union through the Habitats Directive and those that grow on calcareous soils are considered a priority due to their rarity in Europe. In this context, the LIFE Uncinata * project, coordinated by the Centre for Forest Science and Technology of Catalonia (CTFC) and in which CREAF participates, has published the most comprehensive report to date on the state of these forests in the Pyrenees -including Catalonia, Aragon and Navarre- and notes that their surface area has increased in recent decades. Despite this favorable trend, the analysis also warns that climate change could reverse the situation.
Specifically, the comparison of aerial photographs from 1956 with current images shows a significant increase in forest cover, which has increased from 18% to 45% in some areas. According to the data, this expansion has been particularly intense in the lower areas of the mountain range, where the forest has colonized former high mountain meadows that were abandoned decades ago.
Jordi Vayreda
The team has also analyzed the future of these forests under different climate change scenarios. The models of the distribution of black pine forests in the future show worrying data, since they could suffer a strong regression due to the lack of suitable climatic conditions. In fact, projections indicate that by 2040 the areas considered most suitable for this species could be reduced by more than 70% and by 2100 almost 100% under the most severe scenario, especially due to the increase in temperature and the increase in the duration, frequency and intensity of droughts. This could cause the forests to move towards higher altitudes "but drastically reduce their presence at lower altitudes and, even, could almost disappear by the end of the century". Although with forest management oriented towards adaptation and resilience to new conditions, this trend could be attenuated.
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Aging forests and free evolution to improve their conservation
Aging forests and free evolution to improve their conservation
Although it has improved, the study also confirms that only 27% of the total black pine forests are in a good state of conservation. To address the situation, one of the actions carried out by the LIFE Uncinata* project to improve their state of conservation and make them more resilient is to promote their maturity, that is, 'ageing' them; "because a mature forest can better withstand droughts or fires , among other disturbances", adds Vayreda. To accelerate maturity, measures are proposed "that imitate natural processes such as protecting old trees, increasing large dead wood and creating small openings in the forest that allow light to enter to favor other tree and shrub species", as Pol Guardis Bedmar, researcher at the CTFC, comments.
The report also shows that, in some stands, time and the lack of disturbances (natural or anthropogenic), have allowed certain elements of mature forests to evolve naturally. “ We have found that allowing the forest to evolve freely in certain areas is also the most effective way to improve its conservation and maturity ,” highlights Víctor Sazatornil, CTFC researcher and project coordinator. For example, the most mature and best preserved black pine forests are concentrated in protected areas of the Pyrenees, especially in the Aigüestortes and Estany de Sant Maurici National Park, but also the Alt Pirineu Natural Park, Cadí-Moixeró and other areas included in the Natura 2000 Network, where there is less human pressure and more protection.
Large dead wood in a black pine forest in the Aigüestortes and Estany de Sant Maurici National Park. Image: Galdric Mossoll
Other proposals in the project also make the use of the forest, such as timber production, compatible with its conservation. Some examples are "applying selective thinning, marking individual trees foot by foot to decide which ones to keep and extract in order to irregularize the structure of the forest. Also promoting key elements for biodiversity in productive forests, such as companion species or the presence of dendromicrohabitats, such as cavities that provide shelter for birds, bats or small mammals", explains Pol Guardis Bedmar.
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Guide decision-making
Guide decision-making
To create this X-ray, the research team combined several data sources, including the comparison of historical aerial photographs, forest inventory data, forest cartography obtained with LiDAR technology and climate models. “We evaluated both the changes in forest area and the state of conservation and the degree of maturity of the forests, identifying the best-preserved areas and determining their vulnerability to climate change,” explains Jordi Vayreda.
The LIFE Uncinata* project is coordinated by the CTFC and involves CREAF, the Forest Property Centre (CPF), the Catalunya La Pedrera Foundation, and Orekan, from the Government of Navarra. The aim of the project, which will end in 2027, is to improve the conservation of the black pine forests of the Pyrenees and ensure their survival in the face of the challenges of climate change. “ This diagnosis, therefore, provides key tools to guide forest management and decision-making , both within the framework of the project and to guide conservation policies by the administration,” concludes Víctor Sazatornil.
