“Trees are planted by themselves, with the help of the wind, birds and mammals”

Story by: Viatori Photography by: Marc Pell/Unsplash Translated by: Carlos Duarte mar 6, Jul 2021

Natural regeneration is the best way to achieve native forests from abandoned farmland. Instead of plastic protectors, let the scrub grow. And instead of repopulation, let birds and rodents bury seeds and let the wind blow them away. “Trees are planted by themselves, with the help of the wind, birds and mammals,” said Tony Juniper, President of Natural England.

The best strategies to get forests, the fastest, cheapest and most valuable for biodiversity, are those with the least human intervention, according to a scientific study carried out in Great Britain. “The natural recovery of forests is free, there is no risk of importing diseases, it captures ozone and helps reduce the risk of floods,” Juniper stressed.

The authors of the study have declared themselves against the restocking with foreign trees, usually with coniferous plantations. They argue that they can “harm wildlife and carbon-storing peatlands. Likewise, they emphasize that it is necessary to learn to “value the scrubland”, which provides refuge for wildlife. “The bush is a festival of wildlife,” said Richard Broughton, lead author of the study.

According to the scientists, passive regeneration through natural regeneration could be an “important tool” in the policy of reforestation of indigenous trees.

In the case of the United Kingdom, it will invest 5.7 million pounds (6.65 million euros) to increase forests in England by planting at least 12 million trees on 185,000 hectares by 2042, applying regeneration passive could mean a “significant saving”.

Jays, “designers” of native forests

The research, published in the journal ‘Plos One’, reveals surprising data, such as that more than half of the trees in the new forests analyzed in the lowlands of England were “planted” by jays (Garrulus glandarius). The study’s findings are applicable throughout temperate Europe, according to the authors.

The scientists, using field studies and sensors, analyzed two agricultural areas abandoned for 24 and 59 years, both adjacent to ancient forests with trees of multiple species. What the authors call “passive reconstitution” of these two sites resisted both the presence of herbivores and the variable climate.

The old fields quickly became indigenous forests without the need for plastic protectors, irrigation or expensive management, just letting nature take its course.

There was a “passive regrowth” mainly thanks to the scattering of the seeds of brambles, thorns and sloes by the thrushes. This thicket provided natural protection to the trees, mainly oaks, which grew from acorns buried in the ground by jays and, to a lesser extent, by the dragging of seeds due to the action of the wind.

“The new wild nature”

In this way, 24 years after they were abandoned, the grasslands had been transformed into young forests with an average of 132 living trees per hectare, of which 57% were oak. It is what scientists call “the new wild nature.”

In the other field studied, 59 years after its abandonment, the old páramo had become a mature forest, with 390 trees per hectare, of which 52% were oak.

Also in this case, the “design” of the forest corresponded mainly to jays and their work in storing acorns during the winter, although birds of the genus Turdus (thrushes, blackbirds and thrushes) and field mice (Apodemus sylvaticus) also helped. notably to the “creation” of the new wooded spaces.

In the UK, birds such as the jay are key to the natural regeneration of degraded land. Photo: Pixabay

The “collaboration” of a harmful invasive species

An invasive species also “collaborated” in the passive reconstitution of forests: the gray squirrel or the Carolinas (Sciurus carolinensis), included in the list of the 100 most harmful invasive alien species in the world of the International Union for the Conservation of the Nature (IUCN). A species that arrived in the United Kingdom from the United States at the end of the 19th century and displaced its native relatives: there are currently 3 million gray squirrels in the country and just 30,000 red squirrels (Sciurus vulgaris).

The study concludes that the colonization by shrubs and trees begins spontaneously shortly after the abandonment of the land, without the need for active reforestation. There is a rapidly developing shrubby scrub phase in the initial two decades after abandonment, which then progresses to growing tree cover and eventually becomes closed mixed forest after approximately 50 years.

In neither of the two fields studied was there human intervention beyond road cleaning. In fact, the forest vegetation developed “without any kind of intervention or management”.

There was no protection against browsing animals, such as the brown hare (Lepus europaeus), the already mentioned gray squirrel, the European rabbit (Oryctolagus cuniculus), the muntjac (Muntiacus reevesi) and the roe deer (Capreolus capreolus), which were “very common or abundant during part or all of the study period ”, but that did not stop the natural repopulation of native trees.

Natural regeneration withstands five notable droughts

Forests regenerate naturally, thanks to the interaction of wildlife with their environment. Photo: Pixabay

Forest regeneration and growth also weathered the region’s hot climate, “with increasingly hot summers since the 1960s” due to climate change. They even withstood five “notable droughts”, those that occurred in 1973, 1976, 1990, 1995 and 2003, which did not prevent the vegetation cover and natural re-populations from continuing to develop.

The researchers highlight in their conclusions that there are similar patterns in the regeneration of pastures in Spain and of old fields in the temperate zones of North America.

“In Western Europe, the shrubby scrub stage in the first decades after abandonment is a ‘key habitat’ for several birds of community concern, such as the musical flycatcher (Phylloscopus trochilus), the great tit (Poecile montanus), the European turtle dove (Streptopelia turtur) and the common nightingale (Luscinia megarhynchos) ”, point out the researchers.

“Subsequent succession to closed and oak-dominated forests favors other species in decline, such as the great tit (Poecile palustris) and the whistling mosquito net (Phylloscopus sibilatrix),” they add.

Reference Report: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0252466

This note was originally published in VerdeYAzul, written by the Spanish journalist Ramón Díaz.

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