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Biodiversity conservation is a key component of sustainability. According to the University of Alcalá de Henares, birds are the most diverse and abundant group of terrestrial vertebrates in Spain and play an important ecological role. Therefore, changes in the abundance of birds, especially the most common ones, can alter the balance of ecosystems.

This project has analysed the population trend of common landbirds in mainland Spain over the last 20 years, and predicts their evolution for the coming decades considering climate change scenarios. According to the entity, the analytical approach proposed to predict the impact of climate change on population trends is highly innovative, so it is expected to have a great scientific impact. In addition, species that could go into decline have been identified and mitigation measures have been proposed to the agents responsible for the management of the territory and the Natura 2000 Network.

The general objective of the project has been to predict the population trend of common landbirds in mainland Spain in response to climate change and to design mitigation strategies to prevent the decline of the affected species.

The specific objectives were as follows:

• To determine how climate limits the abundance of bird species in mainland Spain.
• To evaluate how the climatic limitation of abundance has determined the population trend of species in the recent past (1998-2018), and to estimate the predictive capacity of the models obtained with observed data.
• Predict the population trend of species in future climate change scenarios.
• Identify common terrestrial species whose populations could be reduced in the future as a result of climate change.
• To identify areas of priority attention in mainland Spain for the conservation of bird species whose populations could be reduced in the future.
• Identify opportunities for action in priority areas to prevent and mitigate the decline of common landbird species as a result of climate change.
• To transfer the results of applied interest of the project to the competent authorities in the field, to communicate the results of scientific interest to the research community and to disseminate the results of the project to the general public.

• Preparation of the database of bird abundance in mainland Spain, based on the raw data of the SACRE programme, of SEO/BirdLife, for the monitoring of population trends of common birds. 68 species were selected from the 130 contemplated in the SACRE program.
• Obtaining climatic variables for the study units, compiling the average temperatures and total rainfall recorded monthly throughout the 20 years considered in the study (1999-2018). In total, 30 climatic variables have been used for each year that have a greater ecological relevance for the birds under study (average temperature, minimum temperature, maximum temperature and precipitation of 5 different periods: winter, breeding, post-breeding, reproductive and annual).
• Modelling of the maximum potential abundance achievable by the species under study along the temperature and precipitation gradient of mainland Spain, which is an indication of the opportunities and constraints that the climate may impose on their maximum population sizes.
• Preparation of the database of observed population trends of the study species over the period 1999-2018.
• Prediction of the population trend of each species in mainland Spain throughout this period.
• Estimate of the predictive capacity of the models for each species studied.
• Extraction of climate data predicted in the future for the whole of mainland Spain, in different climate change scenarios.
• Prediction of the potential abundance and population trend of species for the period 2041-2060.
• Identification of 22 species whose populations in mainland Spain may decline under future climate change scenarios. These are the ones that, according to the models applied, indicate that they could be significantly affected in the future, considering the trend between the predictions of the present and the future.
• Identification of the most suitable future areas for species in decline as a result of climate change. To this end, two maps were drawn up representing the peninsular areas of priority attention, a map for the current period (from 2016 to 2018) and another for the future (from 2041 to 2060), in order to allow comparisons regarding their hypothetical evolution from the present onwards.
• Evaluation of the degree of inclusion of priority action areas in Natura 2000 Network areas, and detection of “conservation gaps”.
• Analysis of land occupation in priority areas.
• Evaluation of the suitability of land occupation in the areas of priority attention for declining species, and delineation of management proposals.
• Dissemination and communication of the project: preparation of a report of the results of the project in book format, an internal analysis report for SEO/BirdLife, 4 scientific articles, publication of two web news, the organization of a seminar, participation in scientific congresses, etc.

In this project, researchers from the University of Alcalá de Henares have analysed the future of 68 species of common birds in mainland Spain in the face of climate change, considering their habitat preferences and their protection through the Natura 2000 Network spaces. Predictions show that some species will be favored while others will see their populations reduced with climate change by the middle of the 21st century. In addition, the conservation responsibility that each autonomous community will have in the future is identified.

Thus, based on the data provided by SEO/BirdLife from the SACRE programme, which allow quantifying the trends in abundance of the species for the period 1998-2019, the entity has undertaken an analysis between the demographic trends recorded and those predicted for the same time window by the models that relate abundance with precipitation and temperature. In addition, with the models of maximum response of abundance to climate, projections have been made of how the abundance of 68 species chosen in the future will vary spatially , showing their degree of overlap with the habitat that is currently ideal for each species and with the current figures of protected areas. All this information makes it possible to detect the needs and priorities of protection by autonomous communities and by species.

The detailed results for each species are collected in a report in book format that is available in the digital library of the University of Alcalá, whose objective is to expand knowledge through an approach to the modelling of the population size of species throughout the peninsular geography, and which has been sent to more than 100 institutions and organisations public and private entities competent in the conservation of Spanish avifauna.

In addition, the conclusions of the study have been communicated to the scientific community and society in general, through participation in the XV Congress of the Spanish Association of Terrestrial Ecology (AEET), the publication of a scientific dissemination article in The Conversation and content on Twitter, as well as the generation of press releases and radio interviews and the preparation of 4 scientific manuscripts.