Climate change is one of the biggest challenges of our century. Along with habitat destruction, they are the main drivers of the global biodiversity crisis. There are more species in danger of extinction than ever before. Many studies show that butterflies are among the species that have responded the most to climate change, usually in the form of northward or elevation range shifts. Climate change affects their life cycles, flight times, essential interactions and ultimately survival.
Parnassius apollo is an exemplary case of these challenges. Since the first half of the twentieth century, P. apollo populations have declined and become rare or extinct in several European countries. The main causes for such a decline are anthropic, such as inadequate shepherding, pollution, tourism, collecting or habitat loss. However, species sensitivity to habitat alteration and climate change also plays a crucial role.
Butterflies go through a series of swift and dramatic transformations during their life circle. This metamorphosis is sensitive to climatic changes since the transformation from one stage to the next is synchronous with the rhythms of nature and similar to many other natural cycles. A lot of butterflies possess a special sensitivity to warm environments. Thus a slight increase in temperature, imperceptible to humans carries vital significance to butterflies. It has triggered new patterns in their metamorphosis process and even driven the creatures out of their native habitats.
One of the ways of species adaption is through changing the time of year at which they are active. Such timing of life circle events is called “phenology”, so when species start things earlier in the year they are said to be “advancing its phenology”. Advances to some extent have been observed in a wide range of butterflies and moths.
Studies show that species with more flexible lifecycles are more likely to benefit from an earlier emergence driven by climate change. Some species are able to go from caterpillar to butterfly twice or more per year, allowing population growth to occur. However, there are also other species that are less flexible and restricted to a single reproductive cycle per year. They have no benefit from emerging earlier. Moreover, species specialising in one specific habitat type tend to be harmed by advancing phenology.
Butterflies on the move
As a result of climate warming native butterflies all over the world are currently on the move. They are leaving their homes and going to places with cooler temperatures. Long migrations possess a lot of perils. Sometimes the obstacles on a way make a move impossible, which brings us to the human role in the lives of butterflies. Habitat fragmentation caused by land development combined with climate change threatens butterflies’ survival, depriving them of safe stopover points where they can rest and replenish their energy.
This migration is particularly visible in mountain regions. Thus studies show significant and constant shifts of butterfly distributions in the eastern Alps towards higher elevations. As these changes differ among species, they might result in serious community modifications with possible effects on species interactions and competition. A particular concern is caused by species with a low disposition to dispersal because they usually remain in one habitat for many generations.
Parnassius apollo populations are small and isolated with distribution restricted to mountain ranges. Global climate change shuffles their vegetation habitat structure, causing plant species to move toward mountain summits. That changes biotic interactions between insects and plants. Climate change also directly affects species distributions, with the elevational distribution of Parnassius species shifting upward on mountains. Yet mountain ranges are finite and even the highest mountains present ecological and evolutionary limits for parnassians.
Protecting one species to protect all the others
As climate change continues, butterflies may find themselves unable to live with us. Due to our reckless treatment of their habitats, we can lose these joyful and beautiful creatures. Yet the protection of butterflies from climate change is important not only for the sake of their beauty. Butterflies play an important role in our ecosystems. Their caterpillars consume large quantities of plants and act as prey for other species. They also act as pollinators of a wide range of plant species. The destruction of butterflies might result in unpredictable cumulative effects for other species in the ecosystem.
Parnassius apollo acts as an umbrella species for the protection of biodiversity on the ecosystem level and habitat mosaics. By protecting the species itself, other species and habitats associated with it, are also protected.