In the last 20 years, 95 million birds have disappeared from the Spanish skies. The vast majority of losses have occurred in an increasingly inhospitable field. The losses have been compensated by two parallel processes also caused by humans: reforestation due to the abandonment of agriculture and the advancement of cities. In these however, the usual species, like the sparrows, are retiring before the colonization of species coming from outside.
The common calandria is a bird of earthy tones with which it blends with its preferred habitat, the crops of cereals and grasslands. Since 1998, the population of calenders in Spain has been reduced by 47.1%, leaving today four million less, according to data from SEO / Birdlife. Similar losses have had species such as the common shrike (-53.8%), the common swallow, with 15 million less (-51.4%) or the quail, which has lost 640,000 of the 860,000 individuals it had 20 years (-73.9%).
Is the general trend among the most common birds observed in other regions of the planet. In other species, such losses would not go so unnoticed hidden behind the millions of birds that remain. What does it matter if there are 30 million less sparrows if there are still another 130 million left? But missing up to half of a huge bird infantry could have catastrophic consequences.
Of the more than 500 bird species that can be seen in the Spanish skies, about 280 are of the so-called residents. And of these, leaving aside the most unique (eagles, vultures, owls ...) there are 110 of those considered common. These are generally small birds, birds or birds, which are counted or counted by millions. Of these, there are 40 species in decline, 44 in increase and 26 stable or with uncertain tendency. Of the first, there are now 95 million fewer. Of the second, 110 million more.
"The total balance is positive, about fifteen million, but we should not lose those 95 million of the declining species because, if they continue like this, in a few decades they will have become extinct," says Juan Carlos del Moral, coordinator of the citizen science program SEO / Birdlife, from which most of Facts about birdlife in Spain.
Beyond the millions of rise or fall, the earthquake is where those millions are lost or won. The case of sparrows aside, the vast majority of birds have disappeared from the fields. And most of the gains have taken place in forest forest or scrubland areas. Birds have also increased in cities, but the story here is very different.
"The disappearance of birds from the field is a trend that has been observed for a long time," recalls the researcher of the terrestrial ecology group of the Autonomous University of Madrid, Manuel B. Morales. Together with his group colleague Juan Traba, this teacher has been looking for the causes of the decline in the changes that agriculture has undergone in recent decades. One of them, as they recently published in Scientific Reports, would be the fallow, his disappearance.
Thickets and forests have increased their population thanks to abandonment of the field and natural reforestation
"The traditional fallow, with the rest of the earth to the rhythm of one year and one time, offered food, shelter from predators and where to nest in the plots at rest, "Morales recalls." With the intensification of agriculture, the modern fallow, in which the land is broken and herbicides are used so that the bad ones do not grow herbs, fulfills its agronomic function but not the ecological one, "he adds.
Birds are not the only ones that lose out. They lose all other members of the ecosystem, including farmers. Among the ecological services offered were pollination, the transport of seeds from one place to another, control insect pests and even weeds. Many species are also natural herbicides. Studies in France have shown how the disappearance of the common lark in Western Europe, where it was counted by millions, has favored the emergence of weed plants, the weed, whose seeds it fed on. The consequence has been the increased use of chemical herbicides.
In parallel to the decline of the birds in the field, there has been an increase in species of forest areas. In some cases, such as that of the papialbo mosquito net (+ 132.5%), the blue climber (+ 147.1%) or that of the capirotada warbler, which has gone from 5 million copies to more than 13 million since 1998, populations have doubled and more. Again human actions seem to be behind. At the same time that the intensification of agriculture has reaped the grassland bird base, the abandonment of less productive land and the withdrawal of extensive livestock has led to scrub, when not the advance of the forest, in many areas earned for forest species.
Something more complex is the reality of cities. Urban environments have seen their bird population grow in recent decades by up to 12%. But it is a trap increase. Most of this increase is due to previously rural species, such as the wood pigeon, which have found in the city a territory free of predators and full of food that humans discard. But explosive growth has occurred in a small group of invasive species such as the Argentine parrot, Kramer's or the Turkish turtledove. At the same time, populations of common swifts, swallows and, especially, sparrows, have declined by millions.
"The current urban planning is increasingly sterile, with less trees, less space between buildings and with increasingly smooth surfaces, which makes cities a less favorable environment for these species," says the Biological Station researcher from Doñana and urban wildlife specialist Álvaro Luna.
The question then arises as to whether it is a mistake to focus conservation efforts on a few unique species such as vultures or eagles. "It is not a mistake because they also need it, but it is insufficient. Focusing efforts on iconic species gives rise to the political game of pretending that things are going well, when in general they are going wrong," says Juan Carlos del Moral, of SEO / Birdlife, who adds: "We are fooling ourselves by saying that the imperial eagle and the lynx are evolving positively. The ecosystem is much broader and the millions of copies of birds that are being lost should not be lost. They are an indicator of quality of life. "
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