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The expansion of the holm oak trees threatens the Montseny newt

A study led by scientists at the CEAB-CSIC and the CREAF warns about the need of measures for protecting the Montseny newt. They say, in a study recently published, that climate change and changes in vegetation cover in the Montseny Natural Park, jeopardize the long-term viability of this species indigenous from Montseny, which is at risk of extinction.

The results of the work indicate that changes in landscape coverage affect water resources as well as the organisms that depend on them, as in this case the Montseny triton (in the picture), a species at risk of extinction. Image: CEAB-CSIC.The Montseny newt is an amphibian named after the mountain massif where it lives. It only inhabits the small streams of the highest parts of the Montseny massif and occupies an area of less than 25 square km. For this reason, the International Union for Conservation of Nature (IUCN) declared this newt as a species at serious risk of extinction.

A study led by José LJ Ledesma, a CEAB-CSIC (Centro de Estudios Avanzados de Blanes-CSIC) researcher, and Anna Àvila, a CREAF researcher, together with experts in biology of the species and climatologists of the Servei Meteorològic de Catalunya, warns that the increase in forest cover in the Montseny can reduce the water flow of the streams, which jeopardizes the project of reintroduction of the Montseny newt.

As the forest cover increases, the water demand by trees increases and stream flow decreases. As a matter of fact, the study warns that this is the main threat for the Montseny newt, more even than the rise of temperature or the lack of rainfall caused by climate change.

The fact that holm oaks are displaced to higher altitudes is, in its turn, a consequence of climate change. The holm oaks are slowly moving to higher areas, occupied until now by heather and where they could not live before, but where they progressively find better conditions of temperature and humidity.

“This displacement will have consequences in the hydrology of the massif, affecting therefore the aquatic habitats”, says Anna Àvila. Given that holm oak trees need for more water than heather and perspire even during drought periods, its expansion will increase the evapotranspiration of the ecosystem, leaving streams with less water.

The study has analysed five year flow measurements in a Montseny stream and its relationship with weather (rainfall and temperature) and vegetation. With this information, the researchers have calibrated a hydrological model that has allowed them to estimate how much water will be in the streams in 2050 and in 2100, according to the possible climate change scenarios. These scenarios were combined with possible forest cover scenarios, based on previous studies.

The main author of the article, José Ledesma, explains: “both climate and hydrological models, as well as vegetation cover scenarios, are uncertain, but different combinations of scenarios indicate that dry periods will be longer and more frequent in the future. This fact reduces uncertainty and gives robustness to the conclusions. ”

Too slow to run away from lack of water

The Montseny newt is virtually an aquatic animal. It lives in the cold, clean and oxygenated waters of streams of beech and holm oak forests. The drought will force the newt to shelter among the rocks for long periods of time or to migrate in search of new environments.

Although much is still unknown about the biology of the Montseny newt, studies indicate that they move very slowly. This low capacity of movement and the fewer adequate streams, could lead to the loss of individuals and eventually to the species extinction.

Albert Montori, a co-author and member of the GRENP group (which stands for the Catalan name “Grup de Recerca de l'Escola de la Natura de Parets del Vallès’), explains that Montseny newt depends more on the aquatic environment than the Pyrenean newt. “Unlike the Pyrenees, the sub-adults of the Montseny newt are as aquatic as adults and larvae. So, in the event of a drought, the entire population is affected”.

Landscape management can help newt to face climate change

The Montseny newt was first described in 2005. To help in its conservation, the local administration (Diputació de Barcelona) obtained in 2016 the LIFE Tritó Montseny project, aimed at deepening the knowledge of the ecology of this specie and assessing its threats. Reintroduction projects have successfully doubled the population, but now the habitat loss jeopardizes this species.

Reintroduction projects have successfully doubled the population of Montseny newt, but now the habitat loss jeopardizes this species.

José Ledesma considers that "from now on, the most important thing is to quantify and define the minimum flow that newt needs and to study whether the animal can adapt or not to drought events."

On the other hand, Anna Àvila believes that “the results of the study can help to manage for species protection. The Park administration could carry out forestry activities to avoid the expansion of the holm oak trees in the most elevated areas of the Montseny massif”. Actually, this expansion is a reality: a previous study developed by CREAF showed that since the second half of the XX century that heather and beach trees of Montseny are being replaced by holm oaks.

Reference article:

Ledesma, J.L.J., Montori, A., Altava-Ortiz, V., Barrera-Escoda, A., Cunillera, J., Àvila, A. (2019). Future hydrological constraints of the Montseny brook newt (Calotriton arnoldi) under changing climate and vegetation cover. Ecology and Evolution, 9, 9736-9747. doi: 10.1002/ece3.5506