It's a perfect spring day for watching butterflies. The sky is clear, the temperature is above 13 degrees and there is almost no wind. The Valdelatas mountain, next to the main campus of the Autonomous University of Madrid, has been dyed yellow by the flowering dandelions and dozens of insects flutter before the watchful eye of a group of entomologists, who write down each specimen and each species they find. . A few minutes from the Faculty of Biology, Miguel L. Munguira began to carry out this transect to observe butterflies 10 years ago, every week between March and September, which is the period in which the adults fly.
The information from each of these routes is just one of the million and a half records that Munguira and his team are working with to publish the Atlas and red book of the butterflies of Spain. The project It will be released in the second half of 2025 and has the participation of some 500 collaborators – including experts and amateurs who love these lepidopteran insects, very sensitive to the effects of climate change – who are helping to fill in the information gaps that exist. in the national territory.
In 2004, Munguira already participated in the publication of an atlas. But on that occasion, 300,000 records from 33 informants were used. Besides, It only covered the peninsula and the Balearic Islands. The new one includes the Canary Islands, Ceuta and Melilla, so the number of species studied has gone from 230 to 257. “We are collecting absolutely impressive information,” says this researcher.
According to his team, between 2004 and 2022 data has been provided for the first time for 25% of the Spanish territory thanks to new studies specific to areas or species, mobile tracking applications and the appearance 10 years ago of the Butterfly Monitoring Program coordinated by Munguira. The data is “oil for scientists,” she says, and will serve to suggest new places that can be included in the network of protected spaces and to know if existing ones are effective, for example. He also explains that this knowledge will allow us to compare the situation of insects with other groups of animals such as birds and see “what is happening with Spanish nature.”
“There will be a file for each species with a representative photo, the flight time of the adults, what the larvae feed on and in what ecosystems we can find them, as well as possible threats, population trends and their conservation status,” he details. Sara Castro, study coordinator. One of the objectives of the work has been to try to establish the distribution limits of some species that resemble each other. To do this, researchers have captured a specimen in order to carry out a study of its genital apparatus or a genetic analysis in the laboratory. Castro warns that, both to capture insects and to use a butterfly net, it is necessary to have permits and inform about the species being investigated. The project is financed by European Next Generation funds and managed by Tragsatec.
Another purpose of the work is to identify information gaps. Those places that no one has yet visited to certify which butterflies live there. The researchers divided the peninsula into 6,260 grids of 10 kilometers on each side and identified that in 569 of them (9.1%) there had never been a record of butterflies. Munguira and his team, made up of Sara Castro, Enrique García, Helena Romo and Enrique Ledesma, have visited as many of those grids as they could. Together with the contributions of volunteers, they have managed to obtain information from 230 more areas. But there are still 339 to explore. Most of them, in Castilla-La Mancha and the Ebro valley.
And this is where citizen science plays a crucial role in this project. The biologists They have launched a campaign to try to fit all the pieces of the puzzle. “We are trying to gather at least some information from each grid. “Something is better than nothing,” summarizes the biologist. It is not necessary to record a transect with the thoroughness with which one works in the Valdelatas one. Simply visit one of these boxes and write down what species are observed, the date and place. The name of the person who took the data is also requested, which will later appear in the atlas.
There are identification guides, but if it is not possible to distinguish the species, you can take a photo and send it to the researchers by email. They recommend searching within the space to study areas with vegetation, with flowers. Butterflies prefer grasslands to forests and clear days. “If you already know a little more, you can use the app ButterflyCount and carry out a 15-minute count, recording all the species and the number of specimens,” explains Castro.
Munguira assures that there is not a single corner where lepidopterans do not live. “I have climbed 3,000 meter peaks and there are butterflies there too; in somewhat desert areas or intensive crop areas, too. “In any place in Spain there are 10 or 20 species,” he says. In the Valdelatas transect there are, for example, about 50 species recorded. This figure can rise to 100 or 120 in areas such as natural parks. The researchers explain that butterflies are “without a doubt” the insect for which the most data is recorded. “This is what is known as charismatic animals. Among insects, which is a group that the general public does not usually like very much, they have the advantage that they are very pretty and easier to identify,” says Castro-Cobo.
The scientists They use butterflies as bioindicators of ecosystems. Any change in them is a warning that something similar could be happening to other groups with which they live. “We have worked a lot with grasslands and we have an indicator that shows us that in the grasslands the butterflies are going downwards, because something similar will be happening to all the animals and plants that also live in that type of ecosystem,” explains the researcher.
One of the new features of the project is the red book, something that had never been done with all the lepidopteran species of Spain. In this part of the work, threat categories are established for the species, which allow us to understand the risk of extinction and the conservation status. When they finish analyzing the data, they will be able to determine how many species are threatened in the country. Munguira explains that, on a European scale, there are 9% of the 500 butterfly species at risk.
“In Spain it will be a similar figure. It means that there may be 20 or 30 species that are clearly threatened,” estimates the scientist. The dangers for lepidopterans come from the intensification of land use (due to urbanization or agriculture) and also from its abandonment, which causes forest areas to proliferate. In addition, there is a third factor that is becoming more and more important: climate change. “In the future it is going to be terrible. Species are going to disappear, especially mountain ones,” laments the biologist.
Recently, Munguira has begun to observe the effects of global warming on the Valdelatas transect. Each time, the butterflies begin to appear earlier and are sometimes observed until October. Furthermore, species that were on the route 10 years ago have disappeared and new ones have arrived. This is the case of Violetilla (Zizeeria knysna) that previously was only observed as far as Aranjuez and in 2022 it will already be seen along the route. One more proof that changes are constant. The researcher shows the specimen that he has found. It is small, with brown wings with a violet sparkle. Munguira smiles and says: “In any miserable place you find very beautiful things.”
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