Butterflies in the city: science, management and citizenship for a greener Barcelona

As cities have grown and populations have concentrated there, the need to integrate nature into urban environments has become evident. In Barcelona, this vision has taken shape thanks, among others, to the research in urban ecology initiated by CREAF in the 1970s that has evolved into current initiatives such as the Citizen Observatory of Urban Butterflies uBMS . During this time, the city has been transforming its urban green space and scientific research, municipal management and citizen participation have aligned to make Barcelona a benchmark in sustainability, biodiversity and the connection between people and nature.

But how did urban ecology research at CREAF come about? Let's start at the beginning.

In the late 1970s, naturalists, sociologists and urban planners around the world began to debate the role of nature in these urban spaces and how they should be understood and managed taking it into account. The first studies on nature in cities were taking place in different parts of the world: Hong Kong, Tokyo and Belgium had already begun working on them. It was as a result of the connection with this last group that Jaume Terradas , founder of CREAF, promoted the first research on urban nature in Barcelona that gave rise to the branch of study of urban ecology. The first concrete result of this research was the book Ecology of a city: Barcelona, by Jaume Terradas and Margarida Parés who, from 1986, would be a leading person in Ecology and Environment at the City Council.

In addition to these studies, there was a very relevant international milestone that finally boosted urban ecology: the 1992 Rio Summit , where the UN debated biodiversity and sustainable development and which gave rise to Agenda 21, an action plan to promote the latter. As a result, Barcelona intensified its efforts to move towards a greener and more sustainable city, taking advantage of the scientific knowledge provided by CREAF, among others.

Jaume Terradas captured all this knowledge that was being generated in the book Urban Ecology. It was published in 2001 and included proposals from the scientific and municipal fields, many of which are still valid and some of which have already become reality.

As for the administration, during this period it also became clear that the human presence in the urban system adds a lot of complexity when planning urban green spaces. This makes close collaboration between research, municipal bodies and citizens essential. The commitment of Barcelona City Council and the Municipal Institute of Parks and Gardens to move towards a greener and more sustainable city is reinforced by scientific advice, with research centres that provide knowledge and ecological criteria to urban planning.

For example, in 2002, Barcelona City Council published its Citizen Commitment for Sustainability , within the framework of Agenda 21. In order to achieve the established goals, the interaction between CREAF, and other research sources, and the City Council became key to contributing to the conception of change. Thus, CREAF's contributions appear such as the updating and digitalization of the existing Ecological Map of Barcelona and the Aula d'Ecologia de la Ciutat conference series, led by Anna Àvila and Jaume Terradas, which were born in 1996, the result of the collaboration that began in 1980 in the field of urban ecology between Barcelona City Council, the Autonomous University of Barcelona and CREAF. The Aula d'Ecologia has its origins in the purpose of consolidating a nucleus of debate on environmental issues.

The studies resulting from the different collaborations between CREAF and the City Council contribute to and inform aspects of the Green and Biodiversity Plan of Barcelona , which was approved in 2013, and also of the Natura 2021-2030 Plan , roadmaps that seek to achieve the different milestones already established in the Commitment and establish new ones.

The collaboration between Barcelona City Council and CREAF has been consolidated and expanded over time thanks to the involvement of several researchers and joint projects. Around 2016, Yolanda Melero and Joan Pino , researchers at CREAF, began to provide technical and scientific support to the city council through various studies and assignments aimed at understanding and managing the city's ecological potential . This concept refers to the capacity of urban ecosystems to offer environmental services that improve the health, well-being and quality of life of citizens . At the same time, the Barcelona Municipal Institute of Parks and Gardens was initiating significant changes in the management of urban green spaces, such as the elimination of chemical phytosanitary products to promote a healthier and more sustainable green infrastructure. In this context, Melero's research on the biodiversity of urban butterflies and their behavior was a clear example of how a research question can become a useful tool for management.

The reason? Butterflies are considered indicators of biodiversity . That is, their richness, abundance and distribution tell us whether the territory they inhabit is more or less hostile to biodiversity in general. Added to this is the fact that they are the protagonists of citizen science projects around the world, with a standardized protocol that can feed research with data and inform the City Council: and this is how the Barcelona Urban Butterfly Observatory uBMS began to be created.

Specifically, uBMS is a citizen science project that has been collecting and providing scientific data to the City Council for seven years. The project is the result of collaboration between citizens and research to effectively monitor the improvement of urban greenery. It was born in 2018 with Melero at the helm and has had the support of the City Council since 2019. As bioindicators, butterflies have become a key organism for studying the Barcelona ecosystem . As protagonists of participatory research that will help promote changes and improvements in the management of urban parks and gardens.

The two great green lungs of Barcelona—Collserola and Montjuïc—concentrate most of its biodiversity. Thanks to the uBMS reports, it is possible to identify which spaces have the greatest potential for biodiversity and carry out specific maintenance tasks there to conserve and enhance it.

Butterflies arrive from Collserola and Montjuïc, but they need to be able to move through the city. In 2019, Melero led the publication of a scientific article that used citizen science data from the uBMS. The article showed that it was necessary to promote connectivity between the city's green spaces : butterflies found barriers to reach and move around Barcelona. The map drawn by butterflies in the city indicates the path for other beneficial species . The Natura 2021-2030 Plan includes this scientific contribution and includes management criteria to improve connectivity, such as biodiversity refuges and the flight of our protagonists. Other more recent research results give us information about the relationship between management and the functional diversity of butterflies.

The consideration of research results in the management of urban green spaces has contributed to supporting some of the changes necessary to move towards a healthier urban ecosystem, made by the Municipal Institute of Parks and Gardens of the Barcelona City Council. These changes involve transforming gardening practices, continuously monitoring green spaces and evaluating planning policies, tasks in which the uBMS plays a key role.

Urban greenery had traditionally been made up of mowed, uniform lawns that were highly dependent on irrigation. Transforming this model meant reconciling the city with seemingly more disordered spaces that were rich in biodiversity. New practices had to be adopted: reducing mowing, allowing spontaneous and diverse species to grow, and prioritizing the use of more drought-resistant native species. This commitment to naturalization has resulted in a greater variety of plant formations, such as grasslands or shrub areas. Today, green spaces are classified according to their frequency and degree of naturalization, and management is based on biodiversity and ecosystem service criteria .

The responsible and technical staff of the City Council and Parks and Gardens have worked hard to transmit and establish this new paradigm. They have promoted training for their Parks and Gardens gardening staff and established a monitoring of the actions in order to establish a gardening that is conciliatory with nature and aligned with the new municipal vision . This transformation of urban greenery and the active collaboration with research have allowed Barcelona to be recognized at a state level by the Spanish Federation of Municipalities and Provinces with the Finalist Award in the IV edition of the Biodiversity Good Practices Award.

Over the years, 101 volunteers have passed through the uBMS. It currently has 40 active people who, from March to November, periodically visit the city's parks and gardens observing and counting butterflies. 2,981 censuses have been carried out since the start of the project until 2024. With these data, an increase in the diversity of the group of generalist butterflies has been detected, which are now more abundant and more frequent. This could indicate that they are better distributed throughout urban parks and gardens, probably due to the changes implemented by the Municipal Institute of Parks and Gardens in the management of urban greenery .

Without the volunteers, there would be no project. Among them, there is an intergenerational interest in biodiversity and sensitivity for a greener city, which increases significantly thanks to participation in the uBMS.

Perhaps the passion and enjoyment that Pau Guzmán highlights derives from what the project brings to the volunteers, who even take on the strong commitment that participation in carrying out the census over the weekend entails. Participation in the project offers them a wide range of learning opportunities: from increasing their knowledge about butterflies —learning to identify them and learn about their habitats— to discovering research methodologies. Furthermore, this knowledge enables them to pass it on to others.

However, if there is one essential element in citizen science, it is the community. This community is built thanks to good coordination, which “accompany you, resolve doubts or problems and motivate volunteers, and it is very grateful because it brings important added value to the project”, as one volunteer explains. As a result of their participation in the uBMS, a network of butterfly hunters has been consolidated in Barcelona, which is also manifested in the desire to add new people from their environment, such as friends and family.

Overall, the uBMS has created a community of involved, trained and connected people , who contribute to research aimed at guiding the management of green spaces and urban biodiversity. A change that they themselves have already begun to perceive and that they recognize as a clear improvement for the well-being of all the citizens of Barcelona.

The uBMS experience shows that collaboration between citizens, science and administration can translate into concrete and positive changes for the city . Urban green spaces have become a living and valuable space for biodiversity and also a tool for improving the quality of life of citizens. But the driving force behind it all is the people: from researchers to technicians and, above all, the volunteers who, week after week, observe butterflies and connect with a new urban culture that integrates nature as an essential part of the well-being and resilience of the city.