Butterflies in danger: Spanish species adapt to heat, but do not escape extinction | Sciences

2023 was the hottest year on record and the third driest summer in Spain since records began six decades ago. The lack of rain particularly affected Catalonia, which ended the year with its worst drought on record, according to the state's meteorological service. People are becoming increasingly aware of the consequences: reservoirs falling to record levels have reduced supplies and imposed restrictions on water consumption. In the natural environment, plants dry up, and butterflies flee from parks and gardens. Although these insects have learned to regulate their body temperature, they are not free from the negative effects of heat, which increases the risk of their disappearance.

Due to their bright colors and fluttering that begins with good weather, there are more than 24,000 recorded species of butterflies. Their diversity goes beyond their shades: these lepidopteran insects use different climate adaptation strategies depending on where they live. This was proven by an international study published in a magazine Journal of Animal Ecology, which found that butterflies in Catalonia are more efficient at regulating their temperature than species in the UK. However, rising temperatures due to climate change are putting Spanish butterflies at greater risk of extinction. There is an impact on their productivity, as they could be spending time hunkering down from the heat, explains Eric Toro Delgado, of CSIC's Institute of Evolutionary Biology and author of the study: “They can't invest that time in reproduction or laying eggs, which “will have a negative impact.” On the population.”

The researchers compared butterflies from these regions because they have different latitudes and temperature regimes. Furthermore, Toro explains, “knowledge of the conditions of the warmer region reflects to some extent what might be found in the future in the cooler region if climate change continues.”

Scientists have found that as temperatures rise, both groups shift to heat-avoidance behavior. In Catalonia, butterflies change their exposure to the sun with changes in their position: “They open their wings more or less and change their direction relative to the sunlight,” the environmental biologist describes. On the other hand, UK residents “rely more on finding suitable microclimates, i.e. areas of somewhat higher or lower temperature, with more or less exposure to wind.”

For the research, scientists measured the body and air temperatures of nearly 800 adult butterflies from 23 different species. For 10 of them, the researchers had comparable data between species from Catalonia and the UK. Despite the differences between the two groups, the researchers noted that when they reached 22 degrees Celsius, the difference between body temperature and ambient temperature decreased. That is, they need to be heated less or not at all. Therefore, if temperatures get too high, they will overheat as well and must stop activity to protect themselves. This change may initially benefit British butterflies, while Spanish butterflies will struggle to survive if they do not adapt quickly enough: “In the UK, they will also end up overheating if global warming continues,” Toro warns. The British species, which relies mainly on shade to stay cool, is at greater risk of population decline due to habitat loss.

The study authors suggest that one reason Spanish butterflies are better at regulating their temperature may be that they have more thermal options available. However, they also resort to searching for areas with lower temperatures, and their displacement is becoming increasingly apparent. Inappropriate and excessive use of fertilizers and pesticides, or the introduction of non-native species, are other threats to these pollinators. In Spain there are 13 listed species List of wild species subject to a special protection regime.

Butterflies are bioindicator species. That is, their behavior and development provide information about the state of the ecosystem in which they live. Furthermore, these scale insects react quickly to changes, which is why they have been used to study the effects of climate change. Therefore, the fact that the number of butterflies has declined due to drought and heat may provide clues to the condition of other insects, such as bees or beetles, and even vertebrate animals.

A greater understanding of how butterflies thermoregulate, as well as understanding of temperature changes, is essential to predict which species are most at risk from climate change. Diverse ecosystems provide these insects with a greater diversity of microclimates, so the authors highlight planting wildflowers and planting more trees as some measures that can counteract habitat loss.

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