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Migratory birds disperse plants in the wrong direction with climate change

Plants Y migratory birds, especially the frugivorous ones that feed on fleshy fruits, maintain a relationship of mutual benefit. While vegetables feed their pulp to birds, the latter spread their seeds wherever they travel and where the plants would never get there on their own.

Most plant species in Europe that are dispersed by migratory birds do so when they migrate to warmer latitudes in the south, which is counterproductive due to climate change

“When they are not migrating, these birds usually spread seeds tens or hundreds of meters, that is, on a local scale. But when they are in migration, they can disperse seeds tens or even hundreds of kilometers, ”he explains to SINC. Juan Pedro González-Varo, researcher in the department of Biology of the University of Cádiz.

On a stage of climate crisisMany species of birds are moving towards colder latitudes, towards areas with more appropriate climates for their survival. But, in these distribution and adaptation processes, plants depend on long-distance seed dispersal, which could be compromised.

This is revealed by a new study led by González-Varo and published in the journal Nature, with the participation of 18 researchers from 13 European research centers. The results show that the majority of plant species in Europe that are dispersed by migratory birds do so mainly when they migrate to warmer latitudes in the south. This is counterproductive to adapt to current climate change scenarios.

A difficult adaptation if it is not towards the north of Europe

According to various studies, the temperature on Earth is moving at speeds that could exceed 100 km per decade in certain regions. “This means that the temperatures that are currently characteristic of a certain site will not be found there in ten years, but 100 km towards colder latitudes, towards the north in our hemisphere,” emphasizes González-Varo.

But how will European forest plant species respond to this rapid global warming through seed dispersal? “If the seeds travel south, they are going in the wrong direction in terms of adaptation to climate change,” he says. Beatriz Rumeu, second author of the study and also a researcher at the University of Cádiz.

The vast majority (86%) of plants are dispersed by birds when they migrate to warmer areas in autumn

“From a climatic point of view, the dispersion towards the north implies potential [para las plantas] to reach cooler latitudes that will soon be favorable due to climate change. On the contrary, the dispersion towards the south implies the potential to go to warmer latitudes that will be even warmer in the near future ”, the scientist underlines to SINC.

Research shows that only a third of the plants of woods Europeans dispersed by birds (35%) have the potential for long-distance dispersal to the north. “In other words, two thirds of the species could be limited in terms of dispersal,” González-Varo clarifies. The vast majority (86%) of the plants are dispersed by birds when they migrate to warmer areas in autumn.

The work shows that the plants that lack the potential for dispersal of seeds towards the north are those that ripen their fruits during a short period of time between summer and autumn; for example the honeysuckle, the hoops or many species of wild cherry trees.

“On the contrary, the plants with the greatest potential for dispersal towards colder latitudes are characterized by having a very long fruiting, as occurs in junipers, mastic, myrtles, wild olive trees or holly, or by having a very late fruiting, as occurs in the ivy”, Details the researcher.

Juvenile blackbird (Turdus merula) eating fruits of aladierno (Rhamnus alaternus). Birds in breeding or non-migration periods, as well as resident birds, often disperse seeds over short distances (generally less than 1 km) that are insufficient for plants to cope with increasingly rapid climate change. / Juan P. González Varo

In their study, the research team relied on plant-bird interaction networks, that is, on bird communities that consume the fruits and disperse the seeds of plant communities. Information on the fruiting period of plants and migratory flows of birds was incorporated into these networks to characterize the potential for long-distance seed dissemination, both north and south.

The work was carried out in forest areas located in Portugal, Spain, the United Kingdom, Germany, Italy and Poland, and included the study of 13 seed dispersal networks that included 949 interactions between 46 species of frugivorous birds and 81 species of plants. of fleshy fruit from European forest communities.

The key, the birds that winter in southern Europe

The birds that have the greatest potential to disperse European plants towards colder latitudes are Palearctic species, which do not cross the Sahara during their migration.

The scientists also determined that, although all migratory birds in Europe migrate in the same direction (from south to north in spring and north to south in autumn), those with the greatest potential to disperse European plants to cooler latitudes are Palearctic species, that is, those that do not cross the Sahara during their migration, but winter in central and southern Europe or in North Africa.

These species are, in general, very common and abundant on the European continent, like the robins, the warbler, the blackbirds, and various species of thrushes. “Although these are common species, the potential for seed dispersal to the north falls on only a handful of species, some of them heavily hunted in the Mediterranean basin, both legally and illegally,” explains González-Varo.

The potential for dispersal to new areas may have consequences for the composition of the forests of the future, since the different species may not equally colonize new territories that allow them to cope with the increase in temperatures.

“The limitation in dispersal could have effects beyond plants, since each plant species is linked to a cast of species of herbivores, parasites, pathogens Y pollinators“, Concludes the scientist for this research is key to understand, stop and mitigate future losses of biodiversity due to climate change.

Reference:

Juan Pedro González-varo et al. “Limited potential for bird migration to disperse plants to cooler latitudes” Nature

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