The phenomenon is silent and evolves discreetly, but the climate change are, little by little, anticipating the arrival of Spring. It was the Copernicus program, the European Union mission for Earth observation, that left one of the most recent alerts: in Almogía, in the Spanish province of Málaga, the almond trees blossomed earlier.
With a satellite image captured on February 12 and published four days later, the European Copernicus mission noticed that the almond trees were giving premature flowers, warning that this could compromise future harvests due to exposure to the cold and asynchrony with pollinating animals. , like bees.
Already in the United States, Spring is paving the way with a month in advance. In New York, temperatures are rising and, in Washington, the famous cherry trees are already in bloom without waiting for mid-March, reveals a Bloomberg news. Quoted in the article, Theresa Crimmins, director of the US National Phenology Network, says: “It’s definitely been an unusually early and warm spring in the Northeast this year; I had been hesitant and didn’t want to overdo it, but it really does seem quite evident.”
The researcher, who is also a professor at the University of Arizona, notes that, in 2017 and 2020, the city of New York had early springs, but this year’s heat will be surpassing them. “Conditions have definitely been much warmer than average in New York since the beginning of the year, and as a result, the plants and animals are definitely starting to wake up,” she confirms.
This arrival is not exactly official, since the seasons are delineated, not by weather conditions, but by equinoxes and solstices. The spring equinox, when night and day last exactly the same time, announces the official arrival of this season in the northern hemisphere and this has nothing to do with the temperature, precipitation or the number of flowers that we see in the park around foot from home.
If, on the one hand, changes in temperature and average annual precipitation make it seem that the seasons are changing, on the other hand, “Spring is perfectly defined”, recalls Filipe Duarte Santos, professor at the Faculty of Sciences of the University of Lisbon and president of the National Council for the Environment and Sustainable Development (CNADS).
However, the line that separates the different seasons is increasingly blurred, as, with climate change, characteristics of some begin to easily pass to others. Plants flowering earlier than expected – as the Copernicus mission and the United States National Phenology Network warned – is yet another example of how climate change is changing the tides of biodiversity.
“What happens is that, as temperatures are higher, the plants are bewildered. Plants or trees that, in the past, flowered only after a certain date, are now flowering earlier”, observes Filipe Duarte Santos.
Helena Ribeiro, professor and researcher at the Faculty of Sciences of the University of Porto (FCUP) and also responsible for the phenological garden at the Geophysical Institute of the University of Porto (IGUP), explains what is bewildering the plants: “From the moment When temperature and photoperiod conditions are favorable again, a cascade of physiological responses is triggered”, he clarifies.
Good weather signals to the plants that they can start to grow and, “with the occurrence of favorable temperatures out of season, as observed in the last two weeks, some species anticipate their cycle”, continues the researcher. Seeing the spring colors even in January or February is like a breath of fresh air on the gray days of winter, but the truth is that changing the routines of plants has social and economic implications, including in Portugal.
a new normal
The image shared by Copernicus raised doubts: after all, isn’t February the month that marks the beginning of the pink and white blossoming of the almond trees? The manuals say that, between the end of January and March, it is common to see several regions of the Iberian Peninsula adorned with almond blossoms, but the climate seems to be switching back and forth between plants and anticipating this moment. They are, sometimes, very subtle differences of a few weeks or days and that can vary from region to region, but they are enough for those who care for these cultures to notice them.
João Ferreira de Andrade, an almond producer at Quinta da Lagoalva de Baixo, in Ribatejo, told PÚBLICO last year that it had already flowered in January, earlier than expected. In the Alentejo, the blossoming of the almond trees was slightly different, starting just a week before the calculations of farmers in certain areas. The phenomenon has different contours from region to region and seems to have come to stay, having been the new normal of the last five years. And this year does not seem to escape the (new) rule.
“[Este ano] there is already some sprouting, but it is being similar to the previous two years. It is likely that, in the species that are more demanding in the cold, as their needs were met earlier, there is some anticipation”, tells PÚBLICO Ana Paula Silva, professor and researcher at the University of Trás-os-Montes and Alto Douro (UTAD).
In Portugal, the heat and the lower probability of late frosts facilitate the production of almonds further south, but now almond trees are multiplying from the north to the Algarve as temperatures rise. Early flowering is a problem to which growers have already adapted, seeking to escape the consequences of a changing planet from an early age by choosing varieties of this plant that are more suited to the climate of each region. Thus, in the North, almond trees that bloom later are planted to prevent them from freezing; in the south, seeing flowering even in January becomes natural.
Almond trees are not an isolated case: there are cherry trees blooming earlier all over the world and chestnut trees and vineyards seem to be on the same path. Also jasmine, “which usually blooms in March, is now blooming in February”, notes Filipe Duarte Santos.
Also in the phenological garden of the IGUP, there are already flowers appearing. “We have already seen some open flowers in the forsythia [lilaseiro chinês] and not populus [choupo]. The floral buds of fagus [faia] have already come out of the phenological state of dormancy. They swelled up and changed color, which usually only happens at the beginning of March”, reports Helena Ribeiro.
It’s not just in spring that this happens. Another example of the way in which the confused movements of the climate leave the plants without certain dates are the harvests, which are carried out earlier and earlier. The fact that average temperatures are higher means that the grapes ripen even in the summer and days at the beach are now being exchanged for the countryside.
“In Portugal, Spain and other Mediterranean countries, the harvests were done in September”, says the president of CNADS. “Now, farmers find it very difficult to take holidays in August, as everyone likes, because they have to harvest in that month.”
Plant rhythm is changing
The influence of climate change on plant routines has long been studied within phenology – the area of botany that studies the different stages of a plant’s development and how these can be influenced by external factors, namely, light and temperature. temperature, variables also related to the seasons.
The longest timeline of plant phenological changes ever made has been published in the journal nature in April last year and the results provide, according to the researchers, “powerful evidence of the impact of global warming in life on Earth”. The data – which include records made over 250 years – show that plant flowering remained stable during the 19th century and, as the global temperature increased, it began to occur earlier and earlier from the first half of the 20th century.
In China, the spring phenology has been advanced by about six days over the last 35 years and, in Switzerland, this number increases to 30 days. In Kyoto, Japan, the year 2021 saw the earliest cherry blossoms in 1200 years.
Another study, published months earlier in AGU Advances, analyzed the start and end dates of the vegetative phase (in which the plant grows, before reproducing) in plants from the northern hemisphere over the last 30 years, comparing changes in temperature with how they responded. What the researchers found was a mixture of plants that flowered earlier and others that flowered later than normal, with the phenomena occurring more frequently in regions dominated by intensive human activity.
As the phenological development of a plant is directly related to the air temperature, which has increased in recent years, science is discovering that “not only has the beginning of the growing season been anticipated, but also the entry into dormancy is being delayed” in plants. In places like Portugal, where the amount of light “is not a critical element”, the air temperature conditions – such as, for example, warmer autumns – may allow “the plants not to go into dormancy so soon”, he clarifies. Helena Ribeiro.
“Trees have memory”
A phenology that, in the words of Filipe Duarte Santos, “is disturbed”, can have long-term consequences for plants, which are programmed to behave in certain ways in a certain climate. Most adapt well to specific differences in temperature, but if the heat that caused the flower to appear earlier is replaced by lower temperatures – as will happen in the next few days – this could “enhance the occurrence of frosts that damage the flower”, recalls Helena Ribeiro.
“Flowers that have not yet opened will also remain closed and there will be a desynchronization in flowering, which could lead to a longer maturation period for the fruit and an extension of harvest dates”, adds the researcher.
However, and why “trees have memory”, long-term climate changes are the most worrying, says Filipe Duarte Santos, who highlights the droughts that have been recorded in Europe. For example, in a montage, ecosystem common in the south of Portugal, trees exist in a very particular balance and “they know how much it has rained in recent years”, explains the professor at the Faculty of Sciences of the University of Lisbon.
It doesn’t matter when it rains, but “if the average annual precipitation decreases as we go through the decades”, the flora will be harmed. “This is the big problem we have ahead of us”, he concludes.
The beauty of Spring arriving earlier seems like something positive, on a map of extreme weather events and melting ice caps. But, in nature, everything is connected and this balance depends on timings perfect. Rising temperatures can have several implications for animals and plants: from mosquitoes and pollen that appear earlier and persist longer, to migratory birds that change their routes and postpone travel.
With plants waking up earlier and going to sleep later, those suffering from pollen-allergic pathologies may have symptoms for longer, according to the alert of the person responsible for the IGUP’s phenological garden. And it doesn’t stop there: if a flower is born earlier, it may no longer exist when a bee arrives to pollinate it. Without pollination, there is no fruit and, without fruit, the nutrition of thousands of animals – including ours – is compromised.