What needs to be done to rebuild biodiversity

What needs to be done to rebuild biodiversity

“Biodiversity” is one of those composite words that seem to be self-explanatory: “diversity of life” understood, for example, as the number of different species in a given place. However, this aspect of biodiversity is only the easiest to grasp, but it is not the only one. We need to make an effort and look beyond the simple etymological meaning of the word. Indeed, the theme of World Biodiversity Day this year is about going beyond conservation and committing to 'rebuilding biodiversity'. What is meant and what commitments does it require.

Natural phenomena have a preponderant physical component, common to the whole universe, and a biological component so rare as to be special, as unique and exclusive to a single planet (as far as we know today). What most distinguishes life from the universal physical component is that it is a "process" rather than a "substance". Even when it actually takes shape, in an oak tree or in a cat, it's not like when a stone or a star takes shape. This makes difficult to describe and understand life in all its manifestations, including biodiversity. But we certainly know that without evolution, life on Earth wouldn't be as diverse.

Apparently it was precisely a "problem of biodiversity" that provided Darwin with the key to arrive at the evolutionary theory. Generations of students have learned of this revelation through the iconographic story of Darwin's encounter with the Galapagos finches. Like Newton's apple, these birds and their diversity are credited with triggering the spark in Darwin that would have led him to conceive his theory. In reality, Darwin missed the biodiversity of the Galapagos finches.

Darwin was convinced that the finches of the different islands were varieties of the same species, whose differences (for example in the conformation of the beak) were no more appreciable than those of the pigeons that he himself raised. When John Gould, the ornithologist to whom he had sent the samples, told him that each variety of chaffinch was actually a different species, Darwin was thunderstruck. Darwin's "eureka" did not arise from how much the finches differed (as textbooks usually report), but from how similar they were despite belonging to different species. Darwin understood that the fact that different species of finches were so similar meant that what was once a single species was fragmenting into many new species, each "in the process of transformation" to adapt to the resources available on its own island. It was evidence that disproved the "fixity of species," which was the dominant theory at the time that ruled out evolution.

This story also tells us more: without something that disturbs their continuity on the territory and their balance with the environment, the species tend to remain unchangedor in any case to vary very little. Biodiversity, like the evolution that produces it, is therefore a consequence of geological-environmental change. If the islands had all provided the same ideal environment for the original species, probably Darwin would have really sampled only one species of finch. In fact, however, Darwin had underestimated the biodiversity in the Galapagos.

Actually it would be more correct to say that Darwin had underestimated the "taxonomic biodiversity" of finches. Taxonomic biodiversity (number of species, genera, families, and so on) is what we perceive best also from a practical point of view: it is the "signal light" of the "biodiversity problem". But it is only the simplified scheme with which we speak of a vast and intricate network of interactions between living organisms and the physical context: like the life from which it takes shape, biodiversity is a "process" (interaction), more than a "substance" (taxonomic quantity ).

The network of interactions from which today's biodiversity emerges is only the latest in an infinite number of textures woven over the course of geological eras; a sort of Penelope's canvas that has been going on for billions of years and to which evolution gives no peace, undoing and re-weaving it each time with a new embroidery; each time a new network of interactions where each species is a "node" equally essential to the integrity of the ecosystem mesh and its balance.

Biodiversity presents itself as a "problem" when, for some reason, there is a rapid loss or excessive weakening of the nodes. Now, if we limit ourselves to considering biodiversity simply as a number of species, we might get the impression that every time a knot breaks or loosens, just make another one here and there to maintain the robustness of the network and "rebuild biodiversity". .

In the nineties I came across a book with a curious title: The Strange Case of Lake Victoria. Natural history of a microcosm in the balanceOf Tijs Goldschmidt. The presentation on the back struck me because it described a story that seemed to me at odds with that of Darwin's finches: in Lake Victoria, Africa, hundreds of different species of minnows had evolved from a single ancestor in a few millennia. All this evolution had taken place in a relatively uniform environment, certainly not discontinuous like that between one island and another of an archipelago, each capable of fragmenting, with its ecological specificity, the continuity of a species and of generating new ones. new from each fragment.

However, the focus of Goldschmidt's book was not on evolution but on its blind spot: extinction. The furu, as the fish of the cichlid family of Lake Victoria are called (in the Swahili language), were going from a frenzied “evolutionary radiation” to a sudden mass extinction. It is estimated that up to 500 cichlid species lived in Lake Victoria in the middle of the last century. A very beautiful biodiversity. Then it was decided to introduce a host, the Nile Perch, much more profitable for the fishing market even if able not only to compete with the cichlids but also to prey on them. Already in the 1980s between 60 and 70% of the species had disappeared. Here is a "biodiversity problem": what can be done to save the remaining furu species? Can we rebuild the richness of biodiversity that was there before?

And here's the point: if we see the "biodiversity problem" limited to the level at which it manifests itself, i.e. as the disappearance of species, we are led to seek a solution by focusing only on that level. Therefore we take action to fence, protect, restore biodiversity. In this protective rush however, we forget about biodiversity as a network, and about the fact that our protection and reconstruction attempts can prove useless, if not as impactful as our actions that caused the problem. This more complex view of biodiversity scares us because it makes us feel powerless. It makes us understand that perhaps our means may not be enough, that it will not be by planting trees on one side of a forest that we will be able to compensate for the imbalance caused by deforestation on the opposite side. Indeed, by doing so we will probably have just triggered another imbalance. This does not mean, however, that then we might as well stay with our hands folded; it means that it is necessary to focus more on preventive approaches based on respect for biodiversity, as a wonderful phenomenon, which we can protect but cannot restore afterwards.

We must intervene on ourselves before the environment. Economic investments and targeted interventions are not enough (although they are indispensable); above all, a profound cultural change is needed. We must become aware of the fact that we have transformed the planet into a lake all to ourselves, and that we are much more numerous and voracious than the Nile perch. If we haven't got there yet, then this is the awareness we should aim for, on World Biodiversity Day and on subsequent ones.

*Domenico Ridente is a researcher at the Igag (Institute of environmental geology and geengineering) of the Cnr



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