The efforts and activism of experts in conservation biology greatly contributed to the emergence, dissemination and success of the notion "biodiversity", which has now become a buzzword as noted by Takacs (1996). But how should we interpret the widespread acceptance by the scientific community of a notion that is often considered a hodge podge of ideas?
Robert Barbault often defines biodiversity as "the living tissue of the planet" (2008), a very (overly?) general definition, but which has the advantage of expressing, above and beyond the diversity of life forms, the almost infinite web of interactions between the organisms present in the biosphere.
A number of different disciplines have adopted the notion and each has produced a scientific definition for different levels in the structure of life. They distinguish the genetic diversity of populations (and of species on a larger scale), the specific diversity (i.e. the number and relative distribution of species) of functional groups (and of ecosystems and landscapes), the functional diversity of ecosystems (i.e. the number and types of interactions between functional groups). It is also possible to link the diversity of habitats to the dynamics of how they are assembled in order to study the functioning of an ecological landscape mosaic. Though the notion of biodiversity itself is fuzzy, it can be subdivided into various precise scientific definitions depending on whether the topic is population dynamics, ecosystem operation or ecosystem complexes. We may therefore wonder how these various biodiversities can legitimately be placed under the single heading of "biodiversity".
One reason is a hypothesis currently studied by ecologists, i.e. that the biodiversities defined for the different levels in the structure of life (a population, functional group, ecosystem, landscape) can all bestow, on each level, the capacity to adapt to changes in that environment.
In abandoning the general concept of E. Odum based on the "balance of nature" (Odum, 1953), scientists now tend toward a dynamic view of ecology and include disturbances as structuring factors in biotic communities. It is now accepted that the environments surrounding us are the product of their history, including the disturbances encountered and those encountered by the other environments with which they interact. The degree of species richness and the structure of ecosystem mosaics are the result of a historic process in which natural and anthropogenic disturbances combine. That transforms the way we perceive human activities because the imbalances caused by people are not necessarily more catastrophic than those caused by nature. We can no longer see humans as the bull in the china shop of natural balances. Human activities and constructions must be included within the scope of ecology (Larrère et Larrère, 1997 ; Blandin, 2009). At the same time, we observe the development of ecological engineering that can be used to restore environments, guide the development of biotic communities, reinforce certain populations or reintroduce species that have disappeared from a given region. The goal of ecology is now to assist in managing nature (Chapuis et al., 2002).
In this dynamic view of ecology, our handling of nature can no longer consist of attempting to maintain its balances, nor protecting the integrity and stability of ecosystems. Even without human intervention, the notions of integrity and balance are relative in a context of perpetual change. Rather than stability, the issue now is the capacity to adapt, i.e. the resilience (Gunderson et Holling, 2001) of populations, environments, environmental mosaics, etc. to the new disturbances confronting them.
There is thus convergence between the new perspectives of scientific ecology and the idea that biodiversity is a good thing for each level in the structure of life where it can be defined and, consequently, for nature in general.
This is where another explanation of the widespread acceptance of biodiversity comes into play. If it can be presented as various descriptive concepts, then biodiversity is a prescriptive notion. That is no doubt due to its origins. Conservation biodiversity developed as a militant form of science whose goal was precisely to preserve biodiversity and to protect it. Similarly, if we return to the image of the "living tissue of the planet", it becomes clear that the term in itself implies that protecting life also means protecting the diversity of life. It is this general idea that is reinforced by the hypothesis that at each level in the structure of life, the various biodiversities are a positive factor for resilience.
Concerning specific diversity, scientists are in agreement that an extinction is underway and it is progressing faster than the other extinctions that the planet has known. Human activities are thought to be responsible through a complex set of intermingled causes, including excessive consumption, systematic destruction of "pests", cutting of tropical and equatorial forests, agricultural and industrial pollution, urbanisation and infrastructure fragmenting habitats. The species eliminated by human activities are the product of evolutionary processes spanning millions of years. There is an intuitively shocking disconnect between activities motivated by short-term interests and their irreversible consequences. They also note that evolution, through a succession of extinctions and speciation phases, tends to increase the diversity of species and that natural selection implies the existence of genetic diversity in populations. An intuition that is difficult to express suggests that it would be unwise to harm these biological diversities which are both the result of natural selection and its raw material. It is the evolutionary potential (on the various levels in the structure of life) that must be preserved in biodiversity (Blandin, 2009).
Biodiversity can thus be considered a positive factor for nature, but it also constitutes a very rich set of resources and is therefore important for humans. Living species, with their genetic heritage and their many interactions are also "natural resources" and the source of "ecological services" beneficial to humans. Human activities render species extinct, but it is not because species have no apparent utility today that they will never have any. We are denying our descendents access to resources that they could have used.
According to Bryan Norton (1991), an ethical system that values only the "resources" that nature can provide can result in effective protection of areas and living beings from abusive exploitation (or neglect), it is simply necessary to widen the notion of "resource". Above and beyond resource use (raw materials and energy, food and therapeutic uses, etc.), we must take into account other "resources" that can be scientific (we hardly know all living species much less their potential), aesthetic (the beauty of certain species, environments and natural landscapes), even symbolic or religious (in spite of their diversity, all human cultures attribute symbolic value (or supernatural qualities) to certain species, certain sites, certain landscapes). Finally, we must take future generations into account if we are to transmit a "natural heritage" capable of fulfilling their future desires and needs. To that end, we may consider that each generation must let future generations, whose needs and desires are unknown, decide for themselves how they want to use the natural "resources". That means that we must not leave behind an environment that has been destroyed and is unfit for human beings (Jonas, 1979). We must also do our best to avoid irreversible situations, i.e. extinct species and irreparable environments. Finally, the more there is genetic diversity within species, specific diversity in environments, habitat diversity in territories, the more it will be possible for future generations to decide how they wish to use their heritage.
Biodiversity, justified as a positive standard by both an expanded anthropocentric ethic and by an ecocentric ethic, intent on preserving the evolutionary capacities of species and environments (to say nothing of the biocentric ethic which, because it attributes an intrinsic value to all living organisms, strives on principle to enhance specific diversity), can be seen as a standard for action and the various biodiversities as evaluation criteria for spontaneous or managed trajectories. However, the fact that there are so many reasons to protect biodiversity also means that we will not all address the same biodiversities.
The prescriptive nature of the notion of biodiversity is also due to the fact that is has become, since the Rio convention in 1992 , a legal and political concept, subsequently integrated in European and national law that the people in charge of public policy must observe (cf. Gosselin et Gosselin, in this publication).
When divided, the notion is descriptive, when taken as a whole, it is prescriptive, it is also a legal concept and an issue in public policies. As such, biodiversity concerns scientists in the various disciplines (systematicians, population geneticists, biogeographers, ecologists) just as much as environmental managers, developers, amateur naturalists, activists for environmental protection, hunters, fishers, etc.
The new scientific and technical context modifies the traditional protection goals in that the issue is no longer to protect nature against human activities. The goal is either to maintain the disturbance regime that produced the present situation, or to redirect, initiate or block, in short to manage trajectories in order to produce a situation deemed preferable to the present one (or to that toward which it would spontaneously tend).
If we succeed in managing natural dynamics, we can target various situations that are more or less favourable to biodiversity and more or less desirable for humans. Efforts to determine the environment in which humans want to live and that would grant the greatest freedom of choice to future generations thus give way to political discussions to decide which state of the world is deemed preferable from the point of view of human activities and from that of nature.
Adoption of biodiversity as a standard for action and of the various biodiversities as evaluation criteria for desirable (or feared) trajectories has important consequences for politics and environmental-protection practices (Larrère et Larrère, 2009).
Action is undertaken in view of goals that can be negotiated and combined with other goals if they can be reconciled. It can be evaluated on the basis of the observed results. We can thus leave behind the opposition between human activities and a "naturalness principle" which previously placed natural processes above change induced by human use of nature and which declared the need to protect nature from humans. That is the good news proclaimed by contemporary ecology, i.e. it is possible to be part of nature and draw benefit from it, without destroying it… on the condition that we make the necessary efforts.
We have long been concerned with "remarkable" species and areas, but the adoption of biodiversity as a positive standard is an invitation to take care of ordinary nature as well.
Finally, working in the field of biodiversity means accepting controversy and debate. Each person, depending on their goals, experience and knowledge can legitimately claim to speak for the elements of biodiversity being negotiated. We must accept debate and compromises, i.e. avoid attempts to impose viewpoints at the expense of all others. The search for compromises implies that each person understand the ideas, but also the aspirations, passions and limitations of all the other persons involved. Each person is encouraged to respect the ideas of others, without necessarily adopting them, and to abandon technocratic procedures in favour of participative approaches.
 The convention declares "the intrinsic value of biological diversity", which corresponds to an ecocentric ethic. It also proposes that the "benefits arising out of … conservation and sustainable use of biological diversity" should be used for "fair and equitable sharing" among human communities. Biodiversity is thus attributed an instrumental, i.e. anthropocentric, value.
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Référence électronique :
LARRÈRE, Raphaël ; LARRÈRE, Catherine, Thoughts on the notion of biodiversity, Revue Science Eaux & Territoires, Public policy and biodiversity, numéro 03bis, 2011, p. 6-9, 15/03/2011. Disponible en ligne sur <URL : http://www.set-revue.fr/thoughts-notion-biodiversity> (consulté le 21/08/2019), DOI : 10.14758/SET-REVUE.2011.3BIS.02.