Barcelona has identified a new butterfly species, the Green Hairstreak (Callophrys avis), for the first time within the city. The uBMS observatory made the discovery weeks ago during a sampling programme at Parc del Laberint d'Horta. This observation brings Barcelona's total to 52 recorded diurnal butterfly species, representing about 26% of all species found in Catalonia.
The Green Hairstreak is a specialist species, flying only from March to May, with a single generation each year. Its survival depends heavily on the presence of two specific plants: the strawberry tree and the rockrose. Diurnal butterflies, like this newly identified one, are considered excellent bioindicators of environmental quality. Their sensitivity to changes in vegetation, climate, and ecological conditions provides valuable information about urban biodiversity.
In their larval stage, these species rely exclusively on a small number of plants. When these plants disappear or decrease, butterfly populations decline rapidly. Butterflies also respond sensitively to the effects of climate change and play a fundamental role in urban ecosystems as primary consumers and as a food source for many predators and parasitoids.
Monitoring Urban Butterfly Populations
The discovery was made as part of the Urban Butterfly Monitoring Scheme (uBMS) observatory. This project, coordinated by the CREAF ecological research centre, has operated in Barcelona since 2018 under an agreement with the Municipal Institute of Parks and Gardens of Barcelona. Currently, nearly 40 volunteers actively participate in weekly butterfly monitoring across 29 city parks and gardens. Visual censuses are conducted between March and April to collect data.
Barcelona also participates in the Catalan Butterfly Monitoring Scheme (CBMS), an initiative by the Granollers Museum of Natural Sciences. The CBMS carries out monitoring along two routes in Montjuïc and El Carmel.
Common Species and Conservation Efforts
Accumulated data from these monitoring efforts show that, despite an increase in the number of species detected, the five most common species currently account for 64% of all observations. This pattern indicates a community primarily composed of generalist species, which are better able to adapt to urban environments. These five species include Pieris rapae (33%), Pararge aegeria (9.80%), Lycaenidae (8.66%), Leptotes pirithous (7.8%), and Lampides boeticus (4.55%).
Barcelona City Council is promoting various naturalisation strategies to support species with more specific ecological requirements. Key actions include establishing urban meadows and grasslands, low-intensity forest management in natural areas such as Montjuïc, Les Tres Turons, Collserola, and the Rec Comtal, and creating biodiversity refuges.
Monitoring data shows a notable increase in butterfly abundance in the city during 2020, coinciding with lockdown measures, reduced intervention in green spaces, and wetter weather conditions. Conversely, a significant decrease occurred during the prolonged drought between 2021 and 2023. Data from 2024 onwards indicates a progressive recovery.
