Ungulates also threaten the very valuable population of Zerynthia cassandra, the butterfly of S. Piero. This splendid butterfly lives only in a very restricted area areale of the Elbe, an island where it had been seen in 1932 by a group of German researchers, in the area of Marciana Marina, and then disappeared, until it was found more than 70 years later, in 2008, by Ornella Casnati and the scholar Leonardo Dapporto, who then scientifically ascertained its uniqueness. We report a text by Dr. Leonardo Dapporto describing the results of the study by the University of Florence. “How many times have we told ourselves that butterflies and fireflies are disappearing?
Just think of the effect of the clean windshield, for which in recent years traveling on the motorway we rarely happen to crush hundreds of insects with the car as often happened in the past. But to move from feelings to certainties and above all from certainties to actions to counter this evident decline you need great study and a lot of dedication. An example comes from the activities carried out in the Tuscan Archipelago National Park to preserve the precious population of Zerynthia cassandra on the island of Elba. Supported by various projects funded by the National Park and the Ministry of Ecological Transition, the researchers of the Department of Biology of the University of Florence, led by dr. Leonardo Dapporto and Legambiente Arcipelago Toscano have been trying to understand for years whether this splendid butterfly is in crisis on the island and what strategies can be put in place to safeguard it.
Since 2017, researchers have been following this population by going to the island every year to count the eggs of Zerynthia laid on the leaves of Aristolochia, a very rare plant that the larvae feed on. After clarifying that butterfly larvae are mostly found on sunny plants at the edge of the bushes, since 2019, in collaboration with Legambiente, a micro-intervention activity has begun aimed at manually cleaning small areas of brambles where Aristolochia plants were already present but suffocated by vegetation. These interventions have produced great benefits to the butterflies in that any small area of one meter in radius cleaned it has hosted the larvae produced by a couple of butterflies on average.
However, the measurements of the eggs also allowed an important assessment of the impact of a herd of goats established in 2019 near one of the classic sites of Zerynthia, a few hundred meters from the town of San Piero in Campo. This massive activity of the goats has greatly reduced the area of the bushes, taking the Aristolochia plants out of their margin and completely prevented the flowering of the herbaceous plants that produce nectar that the adults feed on. The graph below clearly shows that while in areas treated with targeted cuts the number of eggs has increased over the years, in areas used intensively by goats the number has decreased by the same amount (the central level indicates the average number of eggs present on each plant in each year, positive values are therefore sites to be considered good, negative values sites to be considered not good). The sites where no action has been taken are on average just below average but without major variations over time.
What do these data teach us? First of all, it is necessary to monitor biodiversity to understand how it works and take action to protect it. Furthermore, they give us the measure ofimpact of ungulates carried by man on the populations of insects present on an island where these large mammals would not be naturally present. Another useful element, the grazing of goats could be a threat during the spawning period (March-June) while in the rest of the year it could be useful to keep the area clean from shrubs. Now, if on the one hand the Park and the Associations will be able to indicate to the shepherd careful management of the flock in the immediate vicinity of the enclosure, it will not be as easy to manage the presence of other invasive ungulates on the island.
Nobody can convince mouflons and wild boars to avoid the most precious areas for the species we want to protect and we must resign ourselves to a Manichean choice: considerably reduce the presence of these animals up to the eradication from the island or lose part of a biodiversity that has accumulated on Elba with a unique path from the day of its origin. " (Tuscan Archipelago National Park).
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