What is biodiversity?
Biodiversity is the totality of life forms occurring on earth. But biodiversity is also the variety of ecosystems, which in turn are made up of the habitats where different species of plants, animals, fungi and microorganisms live. And each species, in its turn, can be divided into different populations that are also subject to internal diversity, since no one individual is identical to another.
The number of species present in a region is one of the most commonly used ways to express its biodiversity. It is often impossible to obtain this detailed information for all ‘taxa’ (the groups into which living organisms are divided), so we have to work approximately, studying the composition of communities through indicator groups that are better-known or just easier to study.
The illustration presents nine species of butterflies with sometimes similar and sometimes very different colors and shapes to indicate how the diversity is vast but not always easy to identify.
How many living species are there?
Global biodiversity estimates are still very far from accurate. Currently about 1.9 million species have been described by scientists and given a scientific name. Most of the species described are insects, which are in turn home to unique communities of bacteria, archaeans, fungi, algae and viruses: the ‘microbiome’, only a tiny part of which has been studied to date.
Various mushroom species, macro and microscope photos.
Various estimates have been made based on the current rate of knowledge accumulation. One even suggests that between 183 million and 4.2 billion species live on Earth, between 58% and 88% of which are bacteria. Scientists will certainly be kept busy recognising and describing all of this diversity.
Where is biodiversity?
Living species are to be found in almost all of the outermost part of the earth’s crust. They are absent only in glowing lava, while other places that would seem inhospitable to life – such as very hot underwater springs, the ocean depths, underground rock, caves, desert soil and the surface of glaciers – are all teaming with living organisms. Another way of putting it would be to say that life will be found in any part of the Earth that human technology can reach. But it is also found in places our current technology will never explore.
Conservation International (conservation.org) defines 36 biodiversity hotspots — extraordinary places that harbor vast numbers of plant and animal species found nowhere else. All are heavily threatened by habitat loss and degradation, making their conservation crucial to protecting nature for the benefit of all life on Earth.
Conservation InternationalLiving species are not generally distributed uniformly. Some areas host a much greater number of species than others and are therefore considered biodiversity ‘hotspots’. They are the richest terrestrial regions in biological terms, but also the most endangered. Currently, 36 biodiversity hotspots have been established globally.
An area has to fulfil two strict criteria to qualify as a biodiversity hotspot. It must:
- contain at least 1,500 species of vascular plants found nowhere else on Earth ('endemic' species);
- have lost at least 70% of its original primary vegetation cover. Despite its high population density, Italy is very rich in biodiversity, the Mediterranean basin being one of these hotspots.
Some areas are more biodiverse than others, leading to the establishment of Important Plant Areas in all regions of Italy.
What is biodiversity for?
We human beings are one of the many manifestations of biodiversity. We exist thanks to the many different ways we have of interacting with other living things, some unthinkable just a few decades ago. We eat plants and animals and use various parts of them to dress ourselves, build our houses and work the fields. We have close symbiotic relationships with the microorganisms that live in our bodies, which enable us to perform many physiological functions. But above all, we enjoy ‘ecosystem services’, or the set of functions that other organisms perform.
Photosynthesis ensures our supply of oxygen, while use of many plant species and some fungi in medicine improved our quality of life. Even organisms that seemed unlikely to be helpful to us in the past have proven extremely useful in unusual ways. One example is penicillin, the antibiotic that significantly improved our chances of surviving bacterial infections in the 20th century, which was derived from a mould. Avoiding the extinction of a species might mean allowing future generations to benefit in ways that we cannot see in the present.
What are the threats to biodiversity?
Several factors threaten biodiversity by placing species at risk of extinction. The 1992 ‘Earth Summit’ in Rio de Janeiro was the first world conference to bring together heads of state to discuss the environment. During the event, the group of experts gathered by the UN declared the main environmental threats to be:
- habitat destruction, alteration and fragmentation;
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colonisation by ‘allochthonous’ species (from other geographical regions);
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rising temperatures on Earth;
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and depletion of the ozone layer.
The image illustrates the process of loss and fragmentation of a wooded habitat area as a result of human interventions: the creation of ski slopes, roads and tourist centers, in addition to removing soil from the habitat itself, making it disappear there, reduce it to many small fragments impacting on the normal flows of the ecosystem.
Understanding the urgency of certain threats can help us search for and find solutions to human-induced problems. For example, depletion of the ozone layer was found to be caused by release into the atmosphere in modern times of the CFCs (chlorofluorocarbons) widely used in industrial and domestic cooling processes.
Prompt removal of CFCs from refrigerator coils has allowed this situation to improve. Where the other factors are concerned, awareness alone will not suffice: much more incisive action is needed than is currently being taken.
