A forest in which all its specimens are adults, in which there are no young trees, in which other forms of life are missing or these have abnormally low populations are ecosystems that hide the most silent of extinctions, the so-called “forest syndrome empty".
They are"Forests of the undead", as biologists have called them, places where it is"Collapsed"the natural cycle of regeneration of a certain species because the interaction with other living beings necessary for it to take place has been lost.
And it is that the interactions of mutual benefit between living beings make up"Mutual networks" in nature that when they break due to the absence or decrease of any of them they cause this silent death known as the"Empty forest syndrome".
Condemned to die
They are "Forests with plants, but without animals, condemned to degrade and disappear in the immediate future, victims of this lack of living beings that fulfill fundamental ecological functions in them",Pedro Jordano, a researcher at the Doñana Biological Station, explained in an interview with Efe.
In fact, in wasteland forests "The loss of up to three-quarters of its carbon storage potential has been documented," that is to say, "The trees are still there, but not their ecosystem functions", has pointed out.
"There is not a single species on the entire planet that lives alone, without interrelation with other species",Jordano has assured; is the case of the predator and the prey or the parasite and the host, all of them make up "The architecture of biodiversity".
For this reason, for this biologist "ecological relationships or interaction diversity must be taken into account when addressing the loss of biodiversity in an ecosystem".
Because, although there are habitats that persist adequately even if certain species are lost, in other cases"These species are essential for the proper functioning of the ecosystem, which without them collapses completely."
The role of birds
In the case of birds, although most of them are insectivores, there is a second group formed by frugivores, which feed on fleshy fruits, flowers, nectar, pollen or tubers, and that"They are responsible for disseminating the seeds" through their feces or by regurgitation, Jordano explained.
"They are the flower beds of the forest and without them the natural regeneration of many of them, such as tropical forests, would completely collapse", although also in the Mediterranean forest between 50 and 70 percent of the woody species produce fleshy fruits and depend on the dissemination by frugivorous animals.
And any factor that intervenes in the loss of the ecological functionality of the species, either due to its extinction or because its density is residual, puts this balance at risk;"The wolves are in Sierra Morena, but they do not exercise an ecological function in that ecosystem", the expert has pointed out.
Jordano has referred to the alteration of the habitat of the frugivorous species, which need large areas of range;"If the forest is fragmented, these species will not be able to survive and with them the forest itself."
“If the amount or local abundance of frugivorous birds decreases very strongly, the dispersal process of the plant collapses, the ripe fruits dry up in it or are eaten by rodents, herbivores kill the seedling and there is no dispersal process. of the seed that is effective ”.
The complexity of the forest
For this researcher, approach the problem on a global scale"It's discouraging", because they are very complex systems of relationships between species, and the number of species is very high in an ecosystem, from arthropods and pollinating insects, to pollinating or frugivorous vertebrates.
"We are lost if we intend to list each interaction, we have to understand the complexity to focus on which are the most central interactions within the network itself, which groups of species we cannot lose under any circumstances", he stated.
And in this sense,"There are already lines of investigation, this approach is already being taken, there are fronts that are being opened, but their application is lacking."
For Pedro Jordano, the empty forest syndrome is“An insidious form of extinction, which is not perceptible unless we look through a magnifying glass; the trees can be there, they can be adult trees, which flourish, which bear fruit and they fall to the ground, but not a single seed germinates there ”.
By Cristina Yuste