Today, 22nd May, is the International Day for Biological Diversity, a day in which to celebrate the variety of life on our planet. I personally believe that this truly is a special day, even more of several holidays every year we wait for: today we celebrate the feature that make the Earth unique, until proven otherwise, all over the universe. We are part of a living planet and we live thanks to the fact that we are many and diverse.
It is frequent to read or listen to phrases referring to biodiversity as ‘the animals’. Here, I would like to clarify as much as possible this term for, as commonly meant, it can be true only partially. Let us take, for example, an international definition, accepted by many and used in several contexts.
The United Nations define biological diversity as the variability among living organisms from all sources, including, ‘inter alia’, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part: this includes diversity within species, between species and of ecosystems.
From here one well understands how the variety in the animal world is only a fraction of biodiversity, which includes all that lives and the dynamics that characterize it. To put it in simpler words, biological diversity is the richness of life on Earth: plants, animals, organisms, genes contained in every individual and the ecosystems that constitute them as well as the shape and the structure they take, their abundance, their distribution and the interactions between them.
Well, biodiversity is a complex matter, which has to be studied in depth to be completely understood but, at the same time, it is instinctively intuitive since all of us are part of it. An additional clarification is given by distinguishing biological diversity in three different classes:
– genetic diversity, which defines the difference of genes within a given species and hence corresponds to the entirety of the genetic heritage, to which every living organism contributes
– species diversity, which includes the richness of species, measurable in terms of number of the same species present in a given area, or in terms of frequency of species, that is their scarcity or abundance within a habitat
– ecosystem diversity, which defines the number and the abundance of habitats, of living communities and of ecosystems, within which different organisms live and evolve
I believe this last one to be particularly important for the first cause of biodiversity loss impacts on it and that is habitat degradation and fragmentation. This phenomenon can happen for natural causes (floods, volcanic eruptions, tsunami, wildfires, etc..) as well as for profound man-made land changes, first of all deforestation. Always and everywhere very harmful, it is especially impactful in the so called hotspots, term often associated with biodiversity and which is defined as the areas of the planet characterized by very high levels of biodiversity and, at the same time, strongly threatened by humans. However, habitat destruction is not the only threat to biodiversity but in this list we also find pollution, global warming, overhunting and overfishing. I would like to highlight the second threat to biodiversity, not yet mentioned, because it is often underestimated: the introduction of non-native species in a given ecosystem. When species coming from far away are introduced, deliberately or not, in a new ecosystem, it can happen that they fit particularly well and hence they become invasive, breaking ecosystems balance and causing cascading damages that often begin with the extinction of other species. Take a look, for example, to the case of Lake Victoria perch, the extinction of several bird species after the introduction of cats in New Zealand, or, spatially and temporally closer to us, what is happening nowadays in Italy: Louisiana crawfish haunting Padana irrigation channels, Asian giant hornet killing bees, water hyacinth choking lakes and grey squirrel which is making disappear his red cousin are only some examples of a phenomenon much more important than what is believed to be. In fact, alien species can be the cause of soil erosion, destruction of crops, loss of livestock, damage to infrastructure as well as allergies and diseases carriers: this is the case of the tiger mosquito, to which we are nowadays getting used, which originally comes from south-eastern Asia.
It is fundamental to understand what threatens biodiversity in order to be able to preserve it, which must be done for it increases the productivity of ecosystems, which we are part of and upon which we depend. Every species, of every kind, has its specific role within its ecosystem and contribute to its balance and more. It is thanks to biodiversity if ecosystems are able to provide and maintain services, goods and resources from which we, as humans, benefit, sometimes taking it for granted: I am talking about food availability, medicines, extreme natural events moderation, air and water quality, recreational and spiritual services and much more.
What I think is crucial to realize is that we do not have to look at biodiversity as something with which we have to coexist, we cannot consider ecosystems as some areas outside our cities to be preserved. We are biodiversity ad we are part of ecosystems and we have to look after them to take care of ourselves since we are all gears in a big machine that needs all its components. If there would be only a single animal species, soon there would be no animals, if there would be only a plant species, soon there would be no plants, if there would be only one life form, soon there would be no life.
Co-founder of Kukula