Global warming and wildlife migrations

Global warming and wildlife migrations

In recent years, the issue of global warming has aroused many concerns but also perplexity from those who argue that the cause is not human.
However, the scientific community, which perhaps has the most convincing data, is not that of meteorologists but that of zoologists.
So some researchers have tried to understand the phenomenon through data that could confirm or deny the phenomenon of climate change.
One of the questions that scientists have been asking for some time is: what could happen to fish in the oceans due to rising water temperatures?
A team of researchers from the University of Washington tried to answer the question. According to their study, published in the journal Science, warmer waters will not be able to meet the oxygen needs of marine animals in the coming decades. This will cause the migration of different species of fish that will leave the equatorial areas for colder and more oxygen-rich waters. A consequence of the rise in temperature is also that of increasing the metabolism and therefore the search for food, as stated by Curtis Deutsch, a professor among the authors of the study, who states: «this means that aquatic animals could suffer from lack of oxygen in a future with higher temperatures, even if the amount of oxygen remains the same. But we know that oxygen levels in the ocean are declining and will continue to decline as the climate warms.”
In this sense, the marine animals that will be most affected by climate change by 2100, the year in which the temperature will have risen by 3°C, will be three types of fish in particular: the northern cod, the bream pizzuto, viviparous blennid, and a crab, cancer irroratus.
According to the researchers, the equatorial zone would become unlivable for these four species, forcing them to move away, with the disastrous consequence that current marine habitats would undergo dramatic changes. In the best-case scenario, instead, the temperature will rise by just one degree, causing fish to move from their original habitat at a rate of 15 km every decade. All this will also lead to a food crisis for the populations living next to the equatorial oceans, whose subsistence is often based precisely on the availability of fish.
Needless to underline the catastrophic consequences of this scenario.
Furthermore, the increase in temperatures also influences the phenology of the species, therefore their behavior in the various seasons which can interfere with the times and methods of hibernation or diapause.
In others it can affect reproductive success. In still others, it modifies the timing of migrations, unchanged for thousands of years. For other species, the main problem could be dealing with environmental transformations: ever more frequent and vast fires, droughts, or floods and rains, extreme weather events, lack of food. Not to mention that the increase in temperatures also favors the spread of pathogens, their vectors, and therefore of diseases.
Unfortunately, open field research has given an answer to these theoretical models.
In fact, to this hypothetical scenario, which in itself is already worrying, another one is added, sadly confirmed, which is that of bird migrations.
Migratory birds, every year, have to carry out a task which is to return to nest in the place where they were born.
This means that migratory species must arrive at the right place at the right time.
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 enjoy a full spring, a period in which there are more hours of light to carry out all the necessary activities (conquering a territory, a partner, building the nest, raising one or more broods) and in which there is maximum food availability (mostly more insects or their larvae) to raise offspring. Over thousands of years, a perfect synchrony has evolved between the arrival of migratory birds, the hatching of their broods, and the peak of food availability. Some birds, due to their precision in the dates of arrival in Europe, are called “calendar birds”. But today climate change is breaking this synchronicity, which is no longer perfect.
Thus, according to the estimates of other researchers, in Europe, the peak of food availability in spring is anticipated by between 9 and 20 days: migratory birds, consequently, are trying to get to their destination in advance. Many species are reducing the duration of stops during the journey by about 20%, stops which however are used to rest and refresh themselves, to replenish their energy reserves before continuing their journey.
These species, therefore, risk more to buy time and arrive earlier, but the advance they manage to earn is about a week: too little. They would have to reduce the duration of stops by 50% to anticipate 9 days, and by 100% to gain 20. In short, something impossible for small passerines that weigh between 10 and 20 grams and travel 15,000 km in spring and as many in autumn.
Even in autumn, when they should migrate south, they often still linger in Europe, delaying their departure.
Without going into too much detail on the biocenoses linked to birds, it must be said that the decrease in moments of rest, the forced lengthening of some migratory routes is putting a strain on the direct descendants of the dinosaurs with the result that in the last 40 years, according to the most detailed, had a decline of 247 million copies.
All this brings disastrous consequences in the ecological, agricultural and social fields. Birds are the best insecticides we have, since in spring they stock up on insects harmful to us, such as mosquitoes, or to our crops, such as aphids and caterpillars of various butterflies and moths.
Furthermore, the lower bird load leads to a drastic decrease in excrement and carcasses with negative effects especially for phosphates, notoriously very important for agriculture.
Not to forget other fundamental roles such as pollination (which is not performed only by pollinators) and other important information and material exchange activities such as those of seeds.

Among the birds most affected by climate change is the Arctic tern; his is a record in the entire animal kingdom, not just among birds. The Arctic Tern nests around the Arctic Circle, from Alaska to Siberia via North America and Northern Europe. This species spends the winter in the seas and along the coasts of Antarctica. Thus this fish-eating bird, which weighs just 100 grams, makes a round trip of around 80,000 kilometers each year. The record of all records belongs to an Arctic tern nesting in northern Britain which migrated 96,000 kilometres. This elegant seabird, with a V-tail like a swallow’s, can fly 2.5 million kilometers in an average life: it could make 3 round trips from the Earth to the Moon.
These birds, which oversee delicate ecological balances, are in significant decline and risk implementing the so-called domino effect; that is, an ecological repercussion that progressively involves all of us, including men.
Sea turtles are also suffering from climate change and entire populations that nest along Australian beaches are becoming “feminized”: the sex ratio is no longer 50/50, but 98-99% of newborns are female. This occurs because in sea turtles the sex of the newborns is determined by the incubation temperature of the eggs in the sand, and if the temperature exceeds 30°C inside the nest, only females will be born from the 100-120 eggs laid in each nest. And that’s exactly what’s happening to Australia’s green sea turtle population. It is no coincidence that Australia and the Arctic are two of the places in the world that are feeling the most ferocious effects of global warming.
Finally, among those we are mentioning (but the studies are now countless) a study conducted by researchers at the University of Glasgow has revealed that most fish populations are moving towards the north and south poles in order to escape the sea temperatures which are constantly increasing.
Fish are migrating to colder or deeper waters than their natural habitats in order to escape the ever-rising sea temperatures. The importance of water temperature for marine life is crucial. This environmental element has a significant impact on the metabolism, growth and reproduction of marine species.
Many fish species have very narrow temperature windows in which they can survive, so even a small change can make their habitat inhospitable, so moving to new marine territories remains the only option available.
This migration phenomenon has been observed to cause declines in fish populations worldwide, and in some regions, some fish species have even disappeared completely. Scientists have found that changes in the marine ecosystem are happening up to seven times faster than changes happening on land.
The research, which involved 115 different fish species from all seven of the world’s oceans, represents the first global-scale study of its kind.
Furthermore, the research found that fish populations are mainly moving from areas where temperatures rise fastest.
Ultimately it is not so much the meteorological feedback that gives us signals about global warming; factor often disputed by some meteorologists, researchers and deniers.
Global warming is having a significant impact on wildlife migrations in several ways.
Climate change is causing significant changes in the natural habitats of animals, such as rising temperatures, reduction of food resources and the loss of critical habitats such as forests or glaciers. These changes are driving species to migrate to new geographic areas in search of conditions that are better suited to their needs.
Global warming can affect climate zones, shifting the ideal temperature and humidity ranges for different species. For example, some species are migrating to higher latitudes or higher altitudes in search of suitable climatic conditions; which is already leading to the appearance of non-native species in new areas or the disappearance of local species.
The increase in ocean and sea temperatures is affecting the migrations of marine species, such as fish or sea turtles. For example, some fish species are moving to colder waters or looking for new breeding habitats. Sea turtles are affected by variations in sea temperature which affect food availability, reproduction and the ocean currents they use for their migrations.
Global warming is altering the interactions between species that depend on each other. For example, some migratory bird species depend on the availability of certain insects as a food source during their journey. Climate change is interfering with the synchronization between the arrival of migratory birds and the availability of insects (drastically combated with insecticides), which affects the survival of these species.
It is clear that all these studies and their meta-analyses are providing important information for understanding the problem, but the most worrying fact that emerges is that the entire planet is undergoing such a sudden change that has never been seen before (according to the findings analysed). in its history.
Just look at the following data:
– 33% of the world’s soils are degraded. The percentage in Europe rises to 60%, where, in just 10 years, 177,000 square kilometers of land have undergone progressive desertification (an area more than half the size of the Italian territory); remember that a whole series of organisms live in the soil.
– For birds: 247 million fewer specimens than 40 years ago.
– For insects: 46% less mass worldwide (with peaks of 90% in some species); 40% of known species are in constant decline; one third of species are critically endangered.
– For plants: almost a third of existing tree species are at risk of extinction. In all there are 17,510 species, practically double the endangered species of mammals, birds, reptiles, etc., combined.
– Agricultural biodiversity: out of about 6,000 cultivable plant species, those actually used in food production are about 200 and 66% of global agricultural production consists of only 9 species (sugar cane, rice, corn, wheat, potato, soybean , the fruit of the oil palm, sugar beet, cassava).
Furthermore, as described in this contribution, it is precisely the decrease in biodiversity that makes a substantial contribution to global warming.
Thus, to enter the socio-political sphere, as stated by the UN: every year climate change forces about 20 million people to flee. Their right to be protected and helped, however, is very limited. It is therefore a social crisis that affects above all those who contribute least to the causes of climate change.
If we do not understand that at the basis of all this there is a wrong socio-economic model, based on a liberalism that has made colonialism, the exploitation of resources and the free market its god, then we can continue to talk about it as much as we want.
Time is not on our side, but politics must be and to do so it must change its language.
All warned and none excluded.

Guido Bissanti