I. Introduction

Biological diversity, or in short biodiversity, has been defined by the leading Convention on Biological Diversity (CBD) 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 a biological perspective, biodiversity thus encompasses more than the mere diversity of species: it also includes varietal diversity (e.g. of agricultural crops), so-called genetic resources and the variety of ecological processes.

The term "biodiversity" thus covers the variability among living organisms on three levels of diversity:

the diversity of species (plants, animals, microbes, fungi),
the variety of genetic information carried by living organisms,
the variety of ecosystems or habitats.
Biodiversity, as the diversity of all living things, is to be distinguished from geodiversity, although they are interdependent in many ways.

Assessment of biodiversity

Biodiversity is often understood as the number of different species. In order to measure biodiversity not only in terms of quantity, qualitative aspects of biological diversity in a particular area or region are being included in the form of the following parameters: species density, frequency distribution of species, rarity, functional diversity and ecosystem services, diversity in terms of species relationships, endangered species, non-indigenous species, and value for human beings. 

These parameters are used primarily to assess biodiversity and, beyond that, to assign priorities for the selection of areas to be protected by conversation measures.

In view of the high variability of the living it is not possible to assess biodiversity as a whole. The data collected in the aforementioned parameters rather provides insights into the respective parts of biodiversity. For example, estimates on the number of different species range from 5 to 30 million species of animals, plants and micro-organisms. The Millennium Ecosystem Assessment, based on all species that have so far been identified, estimates the total number of species on Earth at 13.6 million. Overall, however, the assessment of biodiversity is associated with a great deal of uncertainty.

Distribution of biodiversity

Biodiversity hotspots are areas that feature a particularly high density of species and ecosystems which are, at the same time, especially endangered. In general, species density increases from the poles to the equator: the largest diversity can be found in the tropics and subtropics, with the tropical rain forests being the richest ecosystems in the world. The deep-sea floor, which remains to a large extent unexplored, is also home to myriad animal species and micro-organisms. Within the marine ecosystems, tropical coral reefs account for the largest diversity of species.

The following map (Fig. 1) shows the distribution of vascular plant species on Earth. Due to several correlations, it can be assumed that a similar distribution applies to animal species. However, a comparable map of the distribution of fauna has not been created yet. It is noteworthy that almost all biodiversity hotspots are located in the Global South.

Ecosystem services and functions

Ecosystem services are services provided by nature or ecosystems, which are useful to human beings. They include, for instance, the provision of freshwater through precipitation and soil filtration, carbon sequestration in vegetable biomass, pollination of plants by insect colonies and climate regulation, but also primary production of plants that are of use to human beings. According to the Millennium Ecosystem Assessment, ecosystem services can be broken down into four categories: supporting, provisioning, regulating and cultural services. 

As part of biodiversity loss, the decimation of ecosystems by human activities may have serious impacts on the reliability of an ecosystem, which in turn may affect human well-being. For example, satellite pictures have shown that coastal areas in the tropics with intact mangrove forests were much less affected by the 2004 tsunami disaster in Southeast Asia than areas where the forests had been cut down.

Biodiversity loss

As it is difficult to determine accurate numbers of species and to precisely quantify diversity (e.g. of ecosystems), the assessment of biodiversity loss is a very challenging task. However, it is a fact that biodiversity is threatened at the global level; this is e.g. reflected in the destruction of ecosystems (such as rain forests or coral reefs) or in the threat of extinction of species (such as the panda or the Przewalski's horse). Key drivers of biodiversity loss are: 1. habitat change, 2. climate change, 3. invasive alien species, 4. overexploitation of species (e.g. overfishing), and 5. pollution, including overfertilisation. In this regard, the regulation of agriculture is of great importance: For example, the results of the global study of the PREDICTS project on land use attribute 13.6 percent of the loss of species in regional ecosystems to agriculture. In addition to helping assess the current loss of biodiversity, its verified causes also help make predictions about expected future biodiversity loss

As a response to the increasing loss of biodiversity, the Convention on Biological Diversity (CBD) was adopted at the United Nations Conference on Environment and Development (UNCED) in Rio de Janeiro in 1992. By the year 2015, 196 countries, including Germany, were contracting parties to this international nature conservation agreement.

II. Ethical aspects

The concept of biodiversity always includes descriptive aspects that relate to measurable and describable characteristics of the diversity of e.g. species. At the same time, the term "biodiversity" is used to refer to the diversity of nature as something that is worthy of protection. Biodiversity protection is often considered a worthwhile objective; yet it can be challenged on philosophical and ethical grounds. The subject of this discussion is how human behaviour towards non-human nature can be justified and which value (or even intrinsic value) can be attached to nature. The moral debate on biodiversity thus mainly focuses on its right to protection. What exactly is the value of biodiversity? Is it a purely instrumental value that has to be contextualised with respect to the benefit for human beings, or does nature, or do specific areas of nature, have value in its/their own right? In addition to a fundamental debate about the value of biodiversity, its protection is also associated with numerous other ethical challenges that arise not only from the different focuses of the various approaches, but are also related to practical problems and conflicts between different groups of people.

Nature and environmental ethics' argumentation often follows basic patterns, which can be broken down into anthropocentric, pathocentric, biocentric and holistic positions. These approaches differ in terms of the range of objects to which intrinsic value is being attached and which are hence directly entitled to protection. All four approaches have in common that they are anthroporelational. This means that the value assigned to nature is reflected in rights to protection that always relate to the human being. Only humans can bear the obligation for protection; only humans have the ability to establish rules and to assume responsibility. However, this can only be generalized with regard to the derived moral duties. Some environmental ethics approaches assume that various entities in nature can be considered valuable completely independently of human value judgments, while others reject this view.

The value of biodiversity for human beings
Anthropocentric (human-only) environmental ethical theories justify the value of biodiversity in its benefit to humans, who, following an anthropocentric view, can be considered the only intrinsically valuable entity. The value of everything else is derived from this central value and only applies indirectly in relation to its usefulness for humans. Accordingly, a direct duty to protect can only be formulated towards humans, but not towards other living beings. This implies that, if the idea is radicalized, biodiversity is completely meaningless on a planet without human life, but a comprehensive demand for the protection of biodiversity can also be derived from an anthropocentric perspective. The decisive factor here is the central importance of intact and species-rich ecosystems for human well-being as well as economic and scientific endeavors. This makes the preservation of biodiversity a question of global and intergenerational justice. The idea that biodiversity should be preserved for human benefit is still the most relevant legal justification today and can be found in numerous international agreements, such as the Convention on Biological Diversity (CBD). In the CBD, biodiversity was declared a "common concern of mankind".  Following Art. 1, it combines the aim of conserving biological diversity with that of the sustainable use of its components, as well as the fair distribution of the thus produced benefits.

Intergenerational justice and the utility value of nature
On the one hand, biological diversity provides mankind with essential resources for sustainable food security, for the development of new medicines and for the discovery and development of industrial raw materials. On the other hand, biodiversity plays a major role in the fields of bionics and bioindication. Furthermore, the so-called ecosystem services are of major direct or indirect importance for agricultural and industrial production processes. In addition to its being utilised for economic purposes, biodiversity is also associated with aesthetic and recreational values, which are difficult to measure in a commercial sense. The beauty of plants and animals, for example, is appreciated by many people who enjoy nature to go on trips or on holiday. However, which components of biodiversity are necessary for the aforementioned uses is a controversial topic and partly unknown. The decision to conserve biodiversity as fully as possible can be justified with reference to the aim of a long-term satisfaction of basic human needs, for example by strengthening the resilience and functionality of ecosystems.

Ethical positions that support the idea of intergenerational justice argue that people living in the present have moral obligations towards future generations, such as people who are currently still very young or have not yet been born, which are expressed, among other things, in the preservation of an intact natural environment as the basis of human life. Although it is debatable what weight should be given to the interests of people living in the future, it is fundamentally true that it is hardly morally justifiable to maximize the benefits of those currently living at the expense of the environment to such an extent that basic human needs can no longer be met at a later date, for example if environmental damage leads to famine and water shortages.

Critics argue that such approaches would sacrifice the interests of people living today to an uncertain and hypothetical future. A philosophically challenging problem lies in Derek Parfit's objection of non-identity: if measures are taken to protect the interests of people living in the future, the causalities in the world are very likely to be altered to such an extent that those who would suffer if measures were not taken would not be born in the first place. In the course of time, a completely different earth population will emerge, but without those who were originally to be protected.

The preservation of the natural basis of life for future generations can also be found in the German Basic Law. Article 20a states: „Mindful also of its responsibility towards future generations, the state shall protect the natural foundations of life and animals by legislation and, in accordance with law and justice, by executive and judicial action, all within the framework of the constitutional order“.

Pathocentrism (greek pathos: suffering), also known as sentientism (latin sentire: to feel, to sense), links the intrinsic value of a living being to its sentience, or more specifically to its capacity for pain or suffering. According to this position, all sentient beings have morally relevant interests and therefore have an intrinsic value, which means that they are worthy of protection for their own sake. The concept of interest is of central importance here - sentient beings have an interest in things that are beneficial to them or in the avoidance of suffering, which does not differ in morally relevant respects from human interests of this kind and must therefore be equally included in moral decision-making. From this, a comprehensive protection claim for biodiversity can be derived, which does not refer exclusively to human interests, but rather instrumentally bases the value of biodiversity in a broader sense in its benefit for species capable of suffering. In a pathocentric way of thinking, interventions in nature and the loss of species are relevant if they influence the feelings of non-human animals and their associated interests. In most cases, the extinction of one species has negative implications for individuals of other species, for example because preferred food sources are no longer available or other important components of a living being's life are lost. The reduction of habitats can also cause relevant forms of damage, for example if there are intensified territorial fights or certain populations become genetically impoverished due to being cut off from other conspecifics and consequently suffer more frequently from diseases.

In biocentrism (greek bios: life) an intrinsic value is ascribed to all living beings, which, similar to pathocentrism, is based on the fact that all living beings have a morally relevant form of interest, sometimes also referred to as teleological aspirations or the will to live. The situation of living individuals can therefore always be related to species-specific ways of life, from which it can be deduced what is good and what is bad for the respective living being, even if most of the interests to be mentioned here may differ greatly from human ones. According to this view, plants, for example, may not have any interests, but there are notable things that are in a plant's interest and can be recognized through scientific observation and recorded in objective lists. According to biocentric approaches, the interests of all living beings must therefore be morally taken into account, but it is controversial to what extent gradations are permissible in the case of conflicting interests.

A moral duty to protect biodiversity arises in biocentrism in a comprehensive sense, which can be justified above all in the interdependence of different species. The extinction of individual species can always be considered problematic if the welfare of other living beings is impaired as a result.

In contrast to the other views presented, holism does not base its claim to protection on the welfare of individuals and the potential harm they could suffer from the loss of other species. Instead, various higher-level entities, such as species or ecosystems, are also ascribed an intrinsic value, which is often based on their system character or their own species-specific interests, which differ from individual interests. In this view, biodiversity can therefore be understood as something intrinsically valuable and worthy of protection.

Conflicts between the different theories

Individualistic approaches, such as pathocentrism, with strong animal ethical implications, can easily come into conflict in practice with holistic approaches that prioritize the protection of systemic aspects. For example, in order to protect an intact ecosystem, it may be necessary to radically suppress introduced and invasive species through heavy and systematic hunting. While such measures can be considered desirable from a holistic perspective, as they can preserve the integrity of the overall system and prevent the extinction of additional species, the hunting can hardly be justified from an individual and animal ethics perspective. Conflicts of this kind cannot be easily resolved and instead require a systemic change in anthropogenic influences on nature or give rise to a fundamental reconsideration of what form of biodiversity can be considered worthy of protection in a heavily human-influenced world.

Suggested citation

German Reference Centre for Ethics in the Life Sciences (2024): In Focus: Biodiversity. URL [date of access]

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