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Increasing the resilience of ecosystems by reducing local impacts is one of the few existing alternatives to mitigate the effects of climate change. In the European Atlantic, laminaria forests (also called kelp forests or kelp forests) are a key coastal habitat that provides important services ecologically, socially and economically. However, these forests are in decline due to the effects of climate change, possibly combined with other more local pressures such as an increase in herbivory.

Despite the importance of these forests and the evidence of regression in many areas of the world, the magnitude of their decline and their socio-economic implications are still not adequately valued in the peninsular Atlantic. According to the University of La Coruña, this lack of knowledge prevents the necessary measures from being adopted to improve the conservation expectations of this key habitat.

The general objective of the project has been to contribute to the improvement of the conservation status of the Laminariales forests, taking as a study area the Atlantic Islands of Galicia National Park (PNIAG), a marine protected area representative of the coastal Atlantic ecosystem.

The specific objectives were as follows:

• To quantify the conservation status of the Laminariales forests in the Atlantic Islands of Galicia National Park (PNIAG) and its surrounding areas.
• To evaluate the role of herbivoredom in the Laminariales forests and to test its control as a measure to restore these forests.
• To evaluate the socioeconomic importance of the Laminariales forests in the northwest of the Iberian Peninsula.

• Monitoring of the conservation status of the Laminariales forests of the PNIAG and surrounding areas and collection of data related to the coverage, biomass and density of the specimens collected.
• Monitoring the presence of potential herbivores, quantifying the number of species of herbivorous urchins and fish in the eight monitored areas. In addition, this database has made it possible to carry out an analysis of the differences in the abundance of urchins and fish between the Laminariales kelp forests of the PNIAG and the surrounding areas at different times of the year.
• Evaluation of the perception of fishermen who regularly fish in the Cíes Islands Archipelago about the loss of the Laminariales forests and the potential causes of this loss.
• Historical reconstruction of the distribution of Laminariales forests in the PNIAG through the traditional ecological knowledge of park users.
• Historical reconstruction of fisheries developed in areas with Laminariales forests, based on structured interviews with fishermen who carry out their activity in the archipelago of the Cíes Islands.
• Current assessment of the economic relevance of fisheries in Laminariales forests.
• Bibliographic review of scientific articles and reports related to the subject and published in the last 15 years and review of national and international reports and publications made in the marine environment of the PNIAG. As a result of this review, the entity has presented three reports, highlighting the importance of kelp forests and explaining the progress of knowledge achieved thanks to the project: “Laminaria forests: Regressive landscapes”, “Laminaria forests in the Atlantic Islands of Galicia National Park” and “Herbivory in kelp forests”.
• Dissemination and communication of the project in the media, publications on social networks, informative conferences and congresses.

The HERBIKELP project has analysed the causes of the deterioration of kelp forests in the Maritime-Terrestrial National Park of the Atlantic Islands of Galicia, as well as its impact on local fishing activity. To this end, an intense bibliographic review has been carried out that has allowed the study of the populations of Laminariales and the herbivory associated with these forests, both globally and regionally.

Likewise, the initiative carried out by the University of A Coruña has made it possible to verify for the first time that fish herbivory is the cause of the collapse of reef-scale Laminariales forests in northwestern Spain. In the study area, the archipelago of the Cíes Islands, the inability of kelp (Laminaria ochroleuca) to form well-developed forests for a few years is due to an excess of herbivorous pressure by the native fish salpa (Sarpa salpa).

The results show that the degradation of kelp forests is an expanding phenomenon, since the fish is able to cause healthy forests to present a degraded state in a very short period of time, without the help of external agents. Thus, in the two years of study, the number of affected forests has increased considerably, and interviews with fishermen in the area confirm that, in recent years, the extent of these forests has drastically decreased in the National Park and in the surrounding areas.

Therefore, this decline can have important ecological and economic consequences associated with the loss of biodiversity and, therefore, the reduction of the ecosystem services required by the region’s fisheries sector. The discovery of the cause of the collapse of these marine ecosystems, caused by the herbivorous pressure of this species of fish, lays the foundations for the evaluation of possible management measures to reduce, or even eliminate, this source of degradation.

On the other hand, from the aforementioned interviews with fishermen in the area, the general perception of fishermen about the decline of these ecosystems has been determined. In general, most of the interviewees have detected the degradation of the Laminariales forests in their fishing areas, but they do not know the reasons, associate them with overfishing or even relate them to the Prestige accident. None of them associate the loss of these algae populations with the effects of climate change, but they do know that the good state of conservation of the Laminariales forests favours the presence of other species and, consequently, improves fishing (ecosystem services).

In addition, from these interviews, it has been possible to reconstruct the distribution of kelp forests in the entire territory of the Maritime-Terrestrial National Park of the Atlantic Islands of Galicia before its collapse. In addition, these interviews have allowed the study of the value chain of three species, traditionally caught by fishermen in the forests of Laminariales: maragota (Labrus bergylta), spider crab (Maja brachydactyla) and octopus (Octopus vulgaris). The study of the traceability map of kombu seaweed (Laminaria ochroleuca) has also been carried out from its harvest to its destination for sale to end consumers.

Finally, within the framework of the project, the results have been disseminated, both on social networks and in other types of media (talks, news, participation in conferences, etc.). In addition, numerous bibliographic references on the subject have been reviewed and four technical-scientific reports have been written for the transfer of knowledge to four regional and state public entities, as well as three scientific publications in journals with an impact factor (JCR), whose purpose is to transmit the results obtained, their conclusions and proposals to the scientific community. Thus, one of these three reports (“Herbivory in kelp forests”) reveals that native herbivorous fish can be large consumers of brown algae and that, probably, their role as deforesters has been underestimated in temperate latitudes.