published on 7 February 2019 in life

The population of monarch butterflies is increasing in Mexico

Good news is arriving from Mexico for the monarch butterfly (Danaus plexippus): recent research has revealed that the population of monarch butterflies wintering in Central Mexico in 2018 increased by 144% against the previous year. This is what emerges from the census conducted in the Michoacán mountains (Mexico), which additionally revealed the presence of monarch butterflies in an area of 6.05 hectares of pine and fir forests, areas increasing over the 2.5 hectares occupied a year ago. The increase in the population and expansion of their distributional area were the direct consequence of the particularly favourable climate, while in 2017 tropical storms and tornadoes contributed to limiting the number.

Monarch butterfly (Danaus plexippus)

Monarch butterflies are known for the incredible migration that they undertake each year: tens of millions, in fact, leave the United States and Canada to make a journey of over 5 thousand kilometres to go and winter in Mexico. These butterflies, which create one of the most fascinating sights offered by nature, are threatened by extinction. Suffice it to say that over the past years the number of butterflies has dropped drastically and that the historical population has decreased by 90%. According to the scientists, the decline of this species is linked to numerous causes, all of them of anthropic origin. These include climate changes, deforestation that has drastically reduced the habitat of the butterflies accustomed to gathering in thousands on trees, massive use of pesticides that eliminate the plants on which the monarch butterflies depend.

Tree branch with monarch butterflies in Michoacán, Mexico

Jorge Rickards, director of the  WWF Mexico, has pointed out that annual fluctuations in populations are very frequent events amongst butterflies, as they are for other insects. Therefore the census this year is certainly positive, but it must not make us think that the species is out of danger. Indeed, there is no certainty that this growth trend will continue in the future too.

In an attempt to save this species, in 2016 the United States, Mexico and Canada signed an agreement and pledged to introduce various conservation initiatives. Mexico, for example, committed to fighting illegal deforestation and is promoting ecotourism, the United States is seeking to recreate some of the monarch butterfly’s habitats, and Canada, lastly, has undertaken to protect a number of areas where this multicoloured insect reproduces.

With the sponsorship of the Italian Ministry of Education, Universities and Research
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