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Hervé Le Guyader

Protecting biodiversity is the is the challenge of our generation


Emeritus professor of evolutionary biology at Sorbonne University, former Director of the Systematics, Evolution and Biodiversity research unit* and author of several books on the theme of biodiversity,  Hervé Le Guyader looks at the world of living organisms from the perspective of a specialist, who sees himself as optimistic.

The word “biodiversity” dates from the early 1980s. How did it come about?
It appeared for the first time in a book aimed at defending the environment. The idea was to encompass all biological diversity within a single term: the genes contained in species, along with species themselves and ecosystems. Biodiversity defines all living things in their immensity, that dizzying wealth that we are constantly discovering. About one and a half million species were listed by the 1980s, compared with a figure now estimated at seven or even eight million!

Amid the catastrophic pronouncements on biodiversity, you are distinguished by a rather optimistic attitude: why is that?
Let’s be clear about the fact that I do not question the official figures showing the erosion of biodiversity. I simply think that we act more effectively by looking at the glass as half full. Disaster is not inevitable. We have two to three hundred years ahead of us to reverse the process. I agree that this is not a long period and there is no time to lose. It is true that if we do nothing, our existence and that of many species would be threatened in the short term, yet faced with this observation, we must above all remain ready to act. The collapse of a population does not mean its extinction, but it does imply that we must act quickly and usefully, by leveraging the correct means. As Isabelle Autissier, Honorary President of the WWF, rightly said, “it is up to our generation to take things in hand and it is time to get started.” I sincerely believe that this is what is happening, that we have realized the scope of the problem and started to act, which gives me reason to be optimistic.

The Earth has already experienced five mass extinctions; how is the current crisis different?
Among these five extinctions, two were particularly severe: the Cretaceous-Tertiary crisis, which saw the extinction of the dinosaurs; and the end of the Permian period, during which, according to paleontologists, 85% to 95% of species vanished. Each time, the living world rebounded and was transformed as well as reinvented. Mammals, birds as well as practically all the vertebrates that make up our fauna today are the result of these catastrophes. What characterizes the crisis we are currently experiencing is that it is due to human activity. For the first time, it is a species – in this case us – that is transforming and impacting the natural environment to the point of endangering it.

The growth of the human population risks accentuating the process in the years to come?
Very serious projections by American scientists indicate that the human population will reach its peak around the year 2050, then stagnate on a plateau before decreasing. These models are based on solid anthropological and economic data, such as the drop in fertility in Western countries, the evolution of customs in Africa and India, along with the gradual decrease in world poverty which is the main cause of environmental damage since it leads to chaotic resource extraction. The strong pressure on biodiversity should therefore continue for another 30 years, during which time we will have to be particularly vigilant to ensure that it is as non-destructive as possible. Then the situation could ease. This is just one scenario, but it is a plausible one.

Is biodiversity more at risk in the poorest areas of the world?
Yes, because the urgency of subsistence takes precedence over all other concerns. In the area of forests alone, the Amazon is undergoing full-fledged ecocide causing the disappearance of many populations, but it is not the only one. The forests of Africa and Asia are also being exploited in an unreasonable and uncontrolled manner.

In which regions of the world is biodiversity faring the best?
As far as the marine environment is concerned, it is in the coldest waters that biodiversity is flourishing better than elsewhere. The Arctic and Antarctic waters are murky because they are rich in plankton. As far as the terrestrial environment is concerned, the opposite is true, with warm tropical and equatorial regions being home to marvelous plant biodiversity from which wildlife benefits fully. The causes are twofold: on the one hand, the heat and humidity favor the development of plants; and on the other, these areas were never affected by the great Quaternary glaciations which extended to the Bay of Biscay!

Among endangered species, some attract our compassion and our mobilization more than others: why is that?
The emotional aspect plays an important role. For example, the collapse of bee populations affects us enormously because these insects are familiar and pleasing to us. That is an excellent thing because it is urgent that we act to repopulate them, something which is currently being undertaken. Yet above and beyond bees, we would be well advised to take care of all the other pollinating insects, because all are experiencing the same drop. Similarly, in the oceans, we are very aware of the fate of magnificent species such as sperm whales and dolphins, but far less so that of plankton, which is the essential food of marine animals. There are endless examples of this type, even though everything is linked in our ecosystems. Biodiversity is a chain in which each element counts and that must be understood in its entirety, so as not to disturb the overall balance.

Like what happened in the Baltic Sea in 2019, when the unplanned development of cods damaged an entire ecosystem?
Absolutely, this example illustrates the fact that the rapid development of a species can lead to the destruction of an entire ecosystem. In the Baltic Sea, the problem arose from the massive use of fertilizers on the coast, which ended up in the waters, promoting the appearance of rich plankton which in turn caused the uncontrolled development of cod. Seals (a protected species fond of cod) arrived in large numbers, attracted by the abundant food. The scenario seemed to be positive, until the shoals of sprats feeding the entire chain fell victim to overfishing and began to dwindle in numbers, leading to the sudden collapse of the fauna across the whole area.

What about birds; can you confirm that their populations are increasing again?
According to studies by English ornithologists – who are the best in the world – the most threatened European species have been protected, which has enabled a rise in their populations. On the other hand, the number of so-called “common” birds, to which less attention has been paid, is decreasing year after year. When I was a child, there were sparrows everywhere in the cities, such as along the quaysides in Paris and on Notre-Dame square... Nowadays, we hardly see them anymore. Here again, it is urgent that we take care of all birds.

Throughout history, humankind has constantly distanced itself from its natural environment. Do you see this phenomenon being reversed today?
Humankind has mainly disconnected itself from time in step with Nature. When people used to travel by mule, they lived in close communion with their environment and had all the time in the world to observe it closely, leading to many physical, astronomical and biological discoveries. Today, the challenges we are having to face in terms of protecting biodiversity require us to rediscover great closeness and intimacy with the living world in order to understand it, love it and protect it. They also oblige us to reconnect with the rhythms of Nature, to reflect on our human condition and how we envisage our society. In this respect, the adventure awaiting us is as much philosophical as scientific.

*The Institute of Systematics, Evolution, Biodiversity is shared by the CNRS, the National Museum of Natural History, Sorbonne University, the École Pratique des Hautes Études and the University of the French Antilles.

Based on an interview by Michèle Wouters
Photos © J. Norwood

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