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This initiative arises, according to the Autonomous University of Madrid, from the need to restore and enhance the role of cattle trails in territorial connectivity (the public network of Spanish cattle trails covers about 125,000 linear kilometers), as habitats of biodiversity, with special emphasis on wild bees, in addition to providing ecological connectivity within and between spaces of the Natura 2000 Network and other protected areas.

The entity highlights that the project has a clear demonstrative nature, since its main objective is to implement actions to restore livestock trails, which, properly managed, can act as a reservoir of biodiversity and provide ecological connectivity.

In this way, the results of the initiative, complementary to the LIFE CAÑADA project, contribute to objectives 1.3, 2.1, and 2.2 of the Strategic Plan for Natural Heritage and Biodiversity, and could also be applied in many other geographical contexts, being easily replicated in the other existing livestock routes in Spain.

The general objective of the project has been to contribute to the conservation of the diversity of wild bees (Apoidea) in several protected areas of the Community of Madrid, belonging to the Natura 2000 Network, through restoration actions on livestock roads that allow their rehabilitation as green infrastructures.

The specific objectives were as follows:

• To assess the state of conservation of the network of cattle trails that are operating or potentially can function as green infrastructures in the Regional Park of the Middle Course of the Guadarrama River (PRCMRG) and the Regional Park of the Upper Manzanares Basin (PRCAM), with special attention to the presence in livestock routes of the critical habitats necessary for the survival of wild species of bees and its possibilities of increasing connectivity between Natura 2000 Network sites.
• Define the criteria for the restoration of cattle trails as green infrastructures and execute these actions in line with the recommendations developed under the State Strategy for Green Infrastructure and Ecological Connectivity and Restoration.
• Test restoration interventions on biodiversity.
• To learn about the social importance of the role of livestock roads today, as well as the importance of wild bees in the agricultural sector and the general public.
• Dissemination and communication of the project.

• Analysis of the geographical and structural characterisation of the surroundings of the cattle trails included in the Regional Parks of the Upper Manzanares Basin and the middle course of the Guadarrama River.
• Carrying out two verification outings in the field to the previously selected locations to check the diagnosis carried out. In this way, it has been possible to confirm on the ground that the cattle trails of the Regional Park of the middle course of the Guadarrama river can constitute spaces of critical importance to host natural and semi-natural habitats and, therefore, refuges for biodiversity.
• Design of the restoration plan and quantifiable indicators for its evaluation (occupation of nests for wild bees, number of germinations and surviving plants in woody hedges, etc.). The interventions included in the restoration plan have consisted, on the one hand, of the construction of three dry stone walls in 16 sections of cattle track, accompanied by two nests for wild bees per wall, and, on the other hand, in the planting of hedges of native woody plants of floral interest in another 16 sections. The construction of the walls has made it possible to increase the reservoirs of biodiversity, and, at the same time, has promoted positive ecological effects from the point of view of the conservation of multifunctionality in the landscape. In addition, the existence of multiple hollows in them with varied shapes and sizes constitutes a source of microhabitats suitable for the activity or refuge of a good number of species of reptiles and invertebrates.
• Restoration of cattle trails in the study areas, through three types of intervention: an installation of dry stone walls, an installation of nests for wild bees in the dry stone walls, and planting of low hedges of woody species of floral interest.
• Conditioning of potential habitats for the nesting of wild bees in the selected livestock routes, so that they resemble as closely as possible the natural nesting structures that may be available to bees in the natural environment and thus contributing to the criteria for the restoration of livestock routes as elements of green infrastructure.
• Field sampling of wild bee populations in restored habitats and control areas. The first sampling was carried out to check the initial state of the bee communities, and the second aimed to know the state of the populations after the installation of the nests. These campaigns have made it possible to control the occupation of wild bee nests, observe their evolution and analyse the richness and abundance of the different species of wild bees on the intervened livestock routes.
• Evaluation of the richness and abundance of Apoidea species present in the habitats and the different areas of the PRCMRG and PRCAM identifying the species of wild bees present, identifying 34 morphotypes of wild bees. In addition, it has been found that nest occupancy has been growing exponentially since April 2021, with 87 nests occupied, to a total of 757 in December of the same year. Finally, a slight tendency to be higher has been observed in landscapes with less area of semi-natural habitats and more area of cultivated habitats.
• Social sampling of the population of the municipalities, with special attention to producers, with the aim of collecting information on the value that the inhabitants of the study area give to livestock routes and wild bees. Thus, 82% of those surveyed knew that cattle trails are protected by law and 89% knew that they are related to transhumance and the local movement of livestock. However, just over half of those surveyed believed that cattle trails provide areas for wild bees to nest; In fact, a great disparity of opinions has been observed regarding the idea that the existence of cattle trails is indifferent to the presence of wild bees in them. In addition, almost 50% of those surveyed said they were little or not at all aware of the role that livestock trails play as reservoirs of biodiversity for wild bees. Therefore, the results of the study have concluded that there is a general lack of knowledge among the population about the ecological role of livestock trails, especially in the conservation of wild bees.
• Dissemination and communication of the project: publications on social networks and the project’s website, dissemination in the media, three days of environmental awareness and education and the holding of a technical workshop on the transfer of results “Case study: Greenbee project”, which was held within the program of the Course “Pollinators: beyond the honey bee”.

The GreenBee project has carried out various interventions on livestock roads in the Community of Madrid in order to promote their role as reservoirs of biodiversity of wild bees (Apoidea), thus enhancing their role as elements of green infrastructure capable of producing tangible ecological effects on local and regional scales. After a cartographic analysis, it was decided to concentrate efforts on the Regional Park of the middle course of the Guadarrama River, where 32 sections of cattle track were selected that had their legal width well preserved and crossed cereal agricultural landscapes.

Subsequently, a restoration plan was drawn up in coordination with the LIFE CAÑADAS project and interventions were carried out in 24 sections, with a length of between 600 and 700 metres each and a variable width depending on the type of livestock route. The actions included the installation of dry stone walls and the planting of aromatic and other small woody plants, in addition to installing 96 nests for wild bees on the walls. Before executing these interventions, a sampling of the wild bee community was carried out in the 32 sections included in the design. This pre-treatment sampling yielded a list of 34 morphotypes of wild bees, unevenly distributed between sections.

On the other hand, intensive monitoring of the occupation of the nests installed in the dry stone walls has been carried out, through visits carried out every 6 weeks. The occupation of beers has shown a marked growth throughout 2021, reaching a total of 757 at the end of 2021. The nests have remained installed once the project is completed and the monitoring of the occupation continues.

In parallel to the interventions on livestock trails, the project has also taken into account the social environment of the municipalities of the Regional Park of the Middle Course of the Guadarrama River, aware of the need to link actions on the territory with social actors. Thus, one of the actions of the project has made it possible to carry out social research on the public’s perception of the ecological role of cattle trails and, in particular, on their importance for the conservation of wild bees. The data show a significant margin for improvement in the population’s knowledge of livestock trails: for example, almost 50% of the 151 respondents are little or not at all aware of the role they can play as reservoirs of wild bee biodiversity.

Finally, in the GreenBee initiative, intense work has been carried out, according to the entity, to disseminate the objectives and results of the project. Part of this dissemination has been carried out in the area of intervention, such as the celebration of the days of return of results at the IES Sapere Aude in Villanueva de la Cañada (Community of Madrid). However, events have also been held at the Autonomous University of Madrid (UAM) and a conference has been held with technicians and managers within the framework of the course “Pollinators: beyond the honey bee”, organized by the Bosque Sur Environmental Education Center and the Api-Agro Symbiosis Operational Group. Finally, the project has also had a presence on the networks, and has its own space on the website of the Socioecosystems Laboratory of the UAM.