Of the many and diverse nightmares that Alfred Hitchcock turned into a cinema, one of the most remembered is that of Los Pájaros (1963), with a sky infested with birds whose intentions were as incomprehensible as alarming. Reality, according to biodiversity experts, should also concern us, but in the opposite direction.
Only in the US and Canada, where a study has been carried out that this Thursday publishes the journal Science , there are 3,000 million fewer birds than there were in 1970. In other words, in less than 50 years one of each has been lost four flying birds (29%). The data does not refer to the extinction of species, but to the abundance of animals. Although a specific type of bird does not disappear, they are becoming less and less .
Both processes, in any case, are related: " Extinction begins with the loss of abundance in individuals, " which, in turn, can cause changes in the ecosystem that are fatal to the species. In addition, birds are an "excellent indicator of environmental health and ecosystem integrity", as they are easier to observe and monitor than other groups of animals.
The threat, therefore, is not reduced to the sky, but is due to such widespread factors as "habitat loss, climate change, unregulated crops and other forms of human (animal) mortality." A large interdisciplinary team, led by the ornithologist Kenneth V. Rosenberg, has had a network of 143 radars and various databases for the preparation of the study, whose conclusion "points to an urgent need to face threats to avoid a future collapse of avian fauna. "
The scientist Arvind Panjabi, from the Bird Conservatory of the Rockies, explained to this newspaper that, although the data have been obtained in Canada and the US, two factors have to be taken into account: the first is that these same birds migrate to South America, where, logically, its number must also be reduced. Although experts in this region "surely do not know."
Which brings us to the second question: "Europe is perhaps the only place with similar long-term monitoring of bird populations, and they are suffering from a loss of similar biodiversity, especially in agricultural lands," warns Pajabi, who foresees Similar decline in all those areas where "agriculture has expanded and intensified through the intense use of herbicides and pesticides in large monocultures ." That is, the study has been done in North America, but the trend is widespread. Throughout the globe, the sky empties itself of birds.
It should be clarified that, in any case, the loss of abundance observed has not affected all species equally, and even some have increased their number. But Panjabi attaches special importance to the fact that "many of those (missing) birds were established species such as sparrows, pigeons or starlings , which previously thrived in our agricultural landscapes."
In fact, radar images show that the decrease in the number of birds has gone hand in hand with the loss of biomass in their migratory routes, which would indicate a relationship between the extension of certain agricultural techniques and the reduction of abundance of Birds: Farms and grasslands make up most of our landscape, "says Panjabi," so the loss of birds in these areas is many of us close to home. "
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