Climate change is changing the life cycles of many animal species. The behaviour of birds is one of the most evident proof of it. We talked about it with Francesca Buoninconti, naturalist and scientific journalist
The consequences of climate change are clear to everyone: extreme weather events, drought, increasing in average global temperature, acidification and deoxygenation of the oceans. This has negative effects on ecosystems and all living species. However, some organisms are more affected than others by these consequences, so that they can be considered as indicators of climate change.
We talked about it with the naturalist and scientific journalist Francesca Buoninconti, author of Senza confini. Le straordinarie storie degli animali migratori.
How can climate change affect animal behaviour?
This phenomenon affects all aspects of animal life, often generating knock-on effects. For example, in our hemisphere, many species are expanding and moving their range northwards or to higher altitudes to combat rising temperatures: plants and animals are literally climbing mountains. The same thing happens in the seas and oceans: many species take refuge in deep waters or move towards the poles in search of colder water. From this point of view it is evident that the species living at high altitude or in glacial habitats are certainly the most at risk on an increasingly warm Earth. We are facing a very rapid loss of biodiversity: the so-called "sixth mass extinction". The increase of the temperatures also influences the phenology of the species, therefore their behaviour in the various seasons: it can interfere with the times and the modalities of the hibernation or of the diapause (the phase of spontaneous arrest of the development of some animals, ed) of some species. In others it can affect reproductive success. In others, it changes the timing of migration, unchanged for thousands of years. For other species the main problem could be dealing with the environmental transformations: increasingly frequent and vast fires, drought, or floods and rains, extreme weather events, lack of food. Not to mention that the rise in temperatures also favours the spread of pathogens, their vectors, and therefore diseases. We could talk about it for days. In summary, the biodiversity crisis is just a symptom of the climate crisis that we have caused.
As an ornithologist, you are particularly interested in migrations. Can climate change also affect the routes of migratory birds? How?
Yes, it mainly affects the timing of migration for many species. To understand how, however, we need to take a step back.
The migratory birds, every year, must keep a promise: to return to nest in the place where they were born. Getting to the right place at the right time is vital to them. The species that nest in Europe spend the winter mainly in Africa and every spring they return here after a journey of thousands of kilometers, crossing three great ecological barriers: the Sahara desert, the Mediterranean and the Alps. They must arrive in time to fully enjoy the spring, a period in which there are more hours of light to carry out all the necessary activities (conquer a territory, a partner, build the nest, breed one or more nestings) and where there is the maximum availability of food (mostly insects or their larvae) to grow offspring. In thousands of years a perfect synchrony has evolved between the arrival of the migratory, the hatching of their nestings, and the peak of alimentary availability. Some birds, for their accuracy in the dates of arrival in Europe, are called "calendar birds". But today climate change is breaking this synchrony. It is estimated that in Europe the peak of food availability in spring comes between 9 and 20 days before: migratory birds, as a result, are trying to arrive in advance at their destination. Many species are reducing the duration of the stops during the trip by around 20%, but stops are essential to let them to rest and refresh, to replenish the energy reserves before continuing the journey. So they risk more to get there early, but the advance they manage to earn is about a week: too little. They should reduce the duration of stops by 50% to anticipate 9 days, and 100% to earn 20. In short, something impossible for small sparrows that weigh between 10 and 20 grams and travel for 15,000 km in spring and as many in autumn. In autumn, when they should migrate southwards, they often still stay in Europe, delaying their departure. This is only the most obvious effect for ornithologists who are accustomed to measuring and studying migratory arrivals and departures, but it is also necessary taking into account the environmental transformations caused by climate change. The greater aridity, the fires, the snow and the ice that melt before and form late not only modify the wintering and nesting areas of the migratory birds, but also those they frequent during the stops. The migratory birds are precise: year after year they always pass by the same points, they always follow the same routes, and they even choose the same islands and wetlands as stopover sites. Migratory birds are trying to cope with climate change, but we should help them. Because they are the best insecticides that we have, as in spring they buy up harmful insects for us, like mosquitoes, or for our cultivations, like aphids and caterpillars of different butterflies and moths.
What is one of the most incredible examples of migration?
Surely the Arctic tern: it has a primate in the entire animal kingdom, not only among birds. The Arctic tern nests around the Arctic Circle, from Alaska to Siberia via North America and Northern Europe. But it spends the winter in the seas and along the coasts of Antarctica. So this fish bird, which weighs just 100 grams, every year goes back and forth on a journey of about 80,000 kilometers. The record belongs to a nesting Arctic tern in the north of Great Britain that has crossed 96,000 kilometers. This elegant sea bird, with a V-tail like that of the swallows, gets to fly for 2 and a half a million of kilometers in an average life: it could make 3 return trips from Earth to the Moon.
Climate change can have negative effects on the survival of some of the most endangered species. Can you give us some examples?
Speaking of migratory animals in general there are two "borderline cases". Reindeer and caribou are great migratory who march for thousands of kilometers. In the last 20 years, however, the world population of this species (Rangifer tarandus) has more than halved: it has gone from 4,7 to 2,1 million specimens, mainly due to climate change. In the Arctic it rains more and more often than snow, and the rain on the ground freezes, preventing the reindeer from eating the lichens which are the only source of sustenance in winter. In this period, moreover, the females are pregnant. Reindeer hooves have evolved to dig in the snow, but they can’t break the ice, so reindeer literally starve to death. And they have no peace even in summer: in the season of births, with increasingly hot summers, the number of parasitic insects that infest their respiratory tract (such as the Cephenemia sp.) or that create pustules under the skin (such as the Hypoderma tarandi) have increased dramatically.
Sea turtles suffer climate change as well, and entire populations that nest along the Australian beaches are "feminizing": the ratio of the sexes is no longer 50 and 50, but even 98-99% of newborns are female. This happens because in sea turtles the sex is determined by the incubation temperature of the eggs in the sand, and if the temperature inside the nest exceeds the 30° C, from the 100-120 eggs laid in each nest will be born only females. And that is what’s happening to the Australian population of green turtles. It is not by chance that Australia and the Arctic are two of the places in the world that are suffering the most ferocious effects of global warming.
One last question: when did you realize that you wanted to be a naturalist? What does it mean today for you to be able to do it also by disseminating science?
I think I always knew I wanted to be a naturalist: the love for animals and nature has always accompanied me. I grew up practically by the sea and "spying" octopuses, jellyfish, sea hares, hedgehogs, crabs and of course fish was the most natural thing. Harder, though, to choose what to specialize in when I get to college. But like all the best things in life, even this choice - specializing in ornithology and becoming a bird-ringer - happened a little by chance and a little for a lucky meeting with professionals, now dear friends.
For several years I have been working only as a scientific journalist, obviously dealing with the issues that are most dear to me. I have always liked to talk about biodiversity, ethology and climate, but passion is not enough. You also need to learn how to choose the sources, writing an article, an episode or a post on social media, using different languages based on the audience and the medium you are using and so on. Sometimes it also means taking sides, when you need to raise awareness on some important and fundamental issues: from the climate crisis to the loss of biodiversity, until the disappearance of coastal dunes and beaches. And it also means having a great responsibility towards those who listen to us, especially the future generations. But this is part of my work as well, and I love it.