As mentioned above, sufficiency can be defined and understood in different ways. Therefore, it is also necessary to consider the respective understanding of sufficiency. Due to the large number of different definitions and following Linz (2002), a first step is to distinguish between a qualitative and a quantitative understanding of sufficiency.

A quantitative understanding of sufficiency refers to views in which sufficiency is aimed exclusively at the mere reduction of resource consumption. The qualitative understanding of sufficiency encompasses this quantitative aspect, but goes beyond it by also including socio-cultural change. This may involve a redefinition of prosperity, among other things.

In the next step, the qualitative understanding of sufficiency was further differentiated and it was examined whether the authors of the publications see sufficiency as being linked to a profound transformation of economic conditions and society. A critical attitude towards economic growth and capitalism, statements on the necessity of ‘degrowth’ and ‘post-growth’, as well as remarks on far-reaching changes in power structures and the distribution of property were evaluated as indications for such an understanding.

In this category, a distinction was made between specific and non-specific connections.

The subcategory ‘unspecific connection’ includes publications that mention biodiversity loss as a reason for the need for sufficiency or imply that sufficiency is necessary for the protection of biodiversity, without explaining this further. Publications that describe how sufficiency contributes to the conservation of biodiversity in greater detail are assigned to the category ‘specific context’.

The publications were – if possible - assigned to a field of action based on the system of Demuth and Heiland (2020). Fields of action are understood here as economic and socially significant areas that are distinguished from one another by functions or tasks. The fields of action were then supplemented by the inductive formation of subcategories.

The fields of action considered are: Consumption, energy, mobility, housing, work, agriculture and food, forestry, mining, travel and tourism, research and teaching, regional development and spatial planning, and nature conservation.

With regard to the field of action ‘nature conservation’, it should be noted that, since only publications that establish a connection between biodiversity and sufficiency were evaluated, the publications ultimately deal with the field of action ‘nature conservation’, since biodiversity conservation is a central aspect of nature conservation. However, the field of action ‘nature conservation’ as defined here encompasses the explicit engagement with social issues of nature conservation, nature conservation policy demands or nature conservation narratives.

The evaluation of the texts in relation to fields of action was carried out through the qualitative evaluation of the text sections dealing with sufficiency. In the case of the scientific texts, the one field of action that was considered was assigned. If several fields of action were considered as examples, no allocation was made. Several fields of action were not assigned to one publication, as the scientific publications did not take an in-depth look at several fields of action. It should, however, be noted that there are overlaps between the fields of action. For the purpose of classifying the content of the publications, and because almost all fields have points of contact with each other, a corresponding differentiation of the fields while at the same time making the classification unambiguous seems heuristically sensible.

The publications of the nature conservation associations were treated differently from the scientific publications with regard to the allocation of fields of action, as these publications often considered fields of action such as mining in relation to nature conservation. In the case of the evaluation of the publications of the nature conservation associations, the assignment to a further field of action was therefore made in addition to the assignment to the field of action nature conservation, provided that this second field of action was a central object of consideration of the publication.

The paragraphs in which the terms biodiversity or sufficiency appeared were systematically analysed and the content was classified according to the categories described above.

In addition to the methodology described above, the translation assistance of DeepL, an AI assistant tool, was used in the preparation of the manuscript.

Sufficiency is understood quantitatively in eleven of the 44 publications according to the definition presented above, and qualitatively in 24 cases. In nine other publications the understanding remains unclear. Here, the term is mentioned without further explanation. Of the 24 scientific texts with a qualitative understanding of sufficiency, 13 mention biodiversity loss/biodiversity only once or twice and 19 only make a general connection between biodiversity/biodiversity loss and sufficiency.

Eleven publications mention that there is a conflict between sufficiency and economic growth (Keck et al. 2017; Pufé 2017; Schiemann and Wilmsen 2017; Sperfeld et al. 2017; Witt 2017; Zahrnt, 2017; Miehe 2018; Biermann and Erne 2020; Dallmer 2020; Berger et al. 2021; Wyborn et al. 2021), so it can be concluded that for them sufficiency is linked to a profound transformation.

In the twelve publications of nature conservation associations examined, sufficiency is understood quantitatively in five cases and qualitatively in four cases. Three publications cannot be clearly assigned.

The extent to which a profound transformation is seen as a prerequisite for sufficiency is not noted in the NABU publications. A BUND publication (2022c) states: “Policies that are primarily oriented towards the goal of economic growth are in stark contradiction to sustainable development and the world’s limited resources” (BUND 2022c, own translation). The WWF publications do not address more fundamental changes in political and economic structures. One exception to this is WWF Germany’s publication by Kind and Engel (2018) which states: “Alternative economic concepts to growth-oriented capitalism include the zero-growth, growth-reduction and sufficiency concepts” (Kind and Engel 2018, p. 76, own translation).

When looking at the links between sufficiency and biodiversity established in the scientific publications, it is striking that the necessity of sufficiency for the preservation of biodiversity is mentioned non-specifically in 32 of 44 publications.

The authors of twelve publications make specific links between the need for sufficiency in the face of biodiversity loss and the positive effects of sufficiency for biodiversity conservation: five publications describe the threat to biodiversity posed by agricultural practices and diets and consider sufficiency as a strategy for reducing this threat (Fehrenbach et al. 2017; Antos 2018; Fabricius 2018; Mok-Wendt 2020; Cohors-Fresenborg et al. 2021; Schlatzer et al. 2021). Three publications (Fehrenbach et al. 2017; Fabricius, 2018; Schlatzer et al. 2021) address the pressure on land use and sufficiency as a strategy to reduce this pressure. Other publications mention the positive and negative impacts on biodiversity that can result from sufficiency in tourism and recreational use (Schrader 2017; Zahrnt 2017; Antos 2018). Concrete positive correlations between sufficiency and biodiversity are shown in two publications for the forestry sector (Lippe et al. 2017; Creutzburg et al. 2020).

In contrast to the scientific publications, the publications of the nature conservation organisations more often consider the cause(s) of biodiversity loss and sufficiency as a way to combat those causes in more detail. For instance, they outline the negative impacts of chemicals (BUND 2022b), resource use in a bioeconomy (NABU 2022) and mining on biodiversity (BUND 2017; Kind and Engel 2018).

NABU publications also problematise the impacts of the energy transition on biodiversity: They highlight that the energy transition must be linked to energy sufficiency (Sothmann 2014; NABU Schleswig-Holstein 2019).

A central aspect of this work is the consideration of the integration of sufficiency into biodiversity protection. As this is an essential task of nature conservation actors, central statements and demands on sufficiency from scientific publications on the field of action ‘nature conservation’ are presented below. Since biodiversity protection is also dependent on the spatial management of various anthropogenic land uses, the contents of publications on spatial planning are also listed.

• For effective environmental protection (as well as fair prices and wages), the “Western consumption model of constant increase cannot be continued” (Zahrnt 2017, p. 43, own translation). Thus, Sufficiency is necessary (see also Immovilli and Kok 2020, p. 21).
• Nature conservation (and conservationists) would have to discuss and reflect on its embedding in the imperial mode of living, “[f]or a sustainable social and economic system will not be achieved with efficiency and consistency strategies alone [...]. Sufficiency strategies are needed that pursue the goal of lower energy and material requirements and raise awareness of the non-material - i.e., emotional and social - dimensions of a ‘good life’” (Leibenath et al. 2021, p. 147, own translation).
• Sufficiency will increase the importance of nature and thus increase the pressure on nature through uses such as domestic tourism and sport. Hence it is suggested to develop sufficiency strategies in the context of nature conservation as well as compensation measures for non-use (Zahrnt 2017, p. 43).
• For the implementation of sufficiency strategies, spatial planning and development, especially with regard to land-intensive economic and settlement developments, will play a decisive role (Hofmeister et al. 2021, p. 8).
• Sufficiency could reduce contradictions between climate protection and nature conservation caused by the energy transition (Sperfeld et al. 2017, p. 8).

Eight out of twelve texts from nature conservation associations focus on the field of action ‘nature conservation’. Concrete statements or demands of the associations that link biodiversity conservation and sufficiency can be summarised under the following keywords:

• Nature-friendly energy transition by saving energy (Sothmann 2014; NABU 2021).
• Absolute resource reduction targets (WWF Deutschland 2020; BUND 2022c).
• Putting a stop to deep-sea mining (BUND 2017).

The other demands or statements of the conservation associations such as “a stronger focus should be placed on social and ecological innovations (sufficiency) for a truly sustainable economy” (NABU 2022, own translation) are less concrete.

Nevertheless, these publications contain proposals such as “no-go areas” for the protection of biodiversity (Kind and Engel 2018, p. 67), which are, however, not linked to sufficiency by the authors.

One reason could be controversies about the political implications of sufficiency as suggested by the following statement by a BUND expert: “[S]ufficiency is […] questioning […] the current economic system and the growth paradigm. And that goes against the fundamental core logic of this society, this economy, this policy” (quoted in Huber 2023, p. 37). In other words, the term ‘efficiency’ is met with greater acceptance because it does not imply a restructuring of the existing economic and social conditions - and is therefore preferred. In contrast, the use of the term ‘sufficiency’ may imply this transformation. Spengler (2018) argues similarly: “In [...] several literature sources, there is talk of sufficiency ‘policies’, which are not policy instruments in the strict sense, but refer to broader socio-economic developments that would require a fundamental change in values and entire programmes of far-reaching political reforms. Examples are the “exit from growth policies”, the “reduction of working hours [...] and the reduction of social inequality in order to reduce luxury and ‘conspicuous’ consumption” [...], which could indeed have significant effects in terms of mainstreaming sufficiency” (Spengler 2018 p. 37).

The lack of clarity of the term sufficiency could be another reason why it is used much less frequently. Linz (2004) for example, writes: “To the uninitiated, [the term sufficiency] says nothing or something wrong” (Linz 2004 p. 47, own translation). For Linz (2004), the meaning of sufficiency is therefore unclear for people who are not familiar with the term, or a completely different meaning is attributed to it. Making the term effective in the public sphere is consequently unpromising in his eyes (Linz 2004, p. 47,).

In this context, however, it is noteworthy that the French government adopted a ‘plan de sobriété énergétique’ (energy sufficiency plan) in autumn 2022 (Gouvernement français 2022). Sufficiency is presented as one of three pillars of the decarbonisation strategy. Energy sufficiency is thus very much present in the French public. Hence, the mainstreaming of the term sufficiency, at least in the area of energy sufficiency, should be possible (cf. also Ore 2022). However, in this plan sufficiency is hardly associated with the need for a ‘deeper transformation’ or ‘growth critique’ by the government. Rather, the use of the term seems to focus primarily on a purely quantitative reduction in energy consumption. Moreover, France seems to be the only country in Europe with a focus on energy sufficiency (Messad 2023). Nevertheless, sufficiency policies are recently taken up more prominently in Germany as well, as publications such as those by Reese et al. (2023) on sufficiency and environmental law or by Nawothnig et al. (2023) on sufficiency as a ‘booster’ for reaching climate protection targets show.

Another possible explanation for the low number of publications dealing with sufficiency and its links to biodiversity is that scientists and/or conservation organisations write about the related issues without using the term ‘sufficiency’, either paraphrasing similar strategies and analyses, or using other terms. Examples of paraphrases without the use of other terms can be found, in Moranta et al. (2022) and Otero et al. (2020).

Moranta et al. (2022) write that economic growth, which is linked to human activity and resource use, is the main cause of biodiversity loss. In order to counteract this, a fundamental change in social values and a downsizing of the economy are required. Otero et al. (2020) make a similar argument. They point out, again without explicitly using the term sufficiency, that “economic growth contributes to biodiversity loss via greater resource consumption and higher emissions” (Otero et al. 2020 2). Therefore, they suggest that the conflict between economic growth and biodiversity conservation needs to be acknowledged in policies (Otero et al. 2020, 2). Thus, both Moranta et al. (2022) and Otero et al. (2020) put forward arguments that - given the diversity of the sufficiency definition - could also be put forward for sufficiency.

One example of a strategy with similarities to sufficiency is degrowth. Hickel characterises degrowth as “a planned, coherent policy to reduce ecological impact, reduce inequality, and improve well-being [by, inter alia, scaling] down ecologically destructive and socially less necessary production (i.e. the production of SUVs, arms, beef, private transportation, advertising and planned obsolescence), while expanding socially important sectors like healthcare, education, care and conviviality” (Hickel 2021, p. 1108). Another concept with similarities to sufficiency is the concept of consumption corridors. In accordance to Fuchs et al. (2021) consumption corridors “describe a space between minimum consumption standards that provide every individual with the ability to live a good life, and maximum consumption standards that keep individuals from consuming in quantities or ways that hurt others’ chances to do the same” (Fuchs et al. 2021 p. 4). It can be concluded from this that strategies with characteristics that could be attributed to sufficiency are discussed in the research without the term ‘sufficiency’ itself being mentioned. However, it is questionable whether the authors are familiar with the concept of sufficiency and whether or not they intentionally use other terms.

Another reason why only a small number of authors of scientific publications have used the term sufficiency to date could be that a discursive link between sufficiency and biodiversity has rarely been established. An expert from BUND Youth provides a possible explanation as to why this is the case: “This also raises the question of framing. So, on the one hand, what are the central problems we are actually referring to? Are we doing this for reasons of global justice, climate justice, biodiversity loss? All of those can be named. What does one refer to? And also: does one use the term sufficiency or not?” (cited in Huber 2023, p. 56). Thus, in addition to raising questions on terminology discussed above, this BUND Youth expert raises the question on how to frame sufficiency, suggesting that a variety of framings are possible. From this argumentation - and in view of the few publications that establish the connection between sufficiency and biodiversity - it can be concluded that the necessity of sufficiency is justified differently, i.e. other links are made between sufficiency and, for example, climate change. Is that the case? And if so, why?

When doing a Google search with the keywords ‘sufficiency’ and ‘climate change’ as well as ‘sufficiency’ and ‘biodiversity loss’ the number of hits for ‘sufficiency’ and ‘climate change’ is almost eleven times as high as the number for sufficiency’ and ‘biodiversity loss’ (972.000 hits and 88.700 hits, as of December 18^th 2023). The conclusion that the need for sufficiency is more frequently justified by climate change than by the loss of biodiversity thus appears to be substantiated, although it should be noted that the content of the hits just mentioned was not analysed.

One possible explanation for the difference in the number of hits is that it is easier to assess the benefits of sufficiency as a strategy for mitigating climate change by calculating the savings in greenhouse gas emissions or energy consumption (see for example Burke 2020; Cordroch et al. 2022). However, even with rather practical approaches to measure biodiversity loss caused by land use, like proposed by Durán et al. (2020), quantifying impacts on biodiversity is more complex. The complexity and the associated difficulty in quantifying the loss of biodiversity could therefore be another reason for the small number of publications that establish a link between biodiversity and sufficiency. Furthermore, this could also be a reason why, even when a link between biodiversity and sufficiency is established, it often remains unspecific.

Another explanation indicated by the keyword search mentioned above as well as by looking at the Google hits for the keywords ‘biodiversity crisis’ compared to the keywords ‘climate crisis’ (74.200.000 hits and 864.000.000 hits, as of February 21^st 2024), is that the climate change crisis appears to be more anchored in the public consciousness than the biodiversity crisis, despite both crises being related and should therefore be considered together (Pörtner et al. 2021).

Another reason for general statements on the link between biodiversity and sufficiency may be that biodiversity as a topic is primarily researched by natural scientists, especially biologists. Sufficiency, on the other hand, is a strategy aimed at changing individual lifestyles and social lifestyles, i.e., it deals with social behaviour. Sufficiency is therefore first and foremost an object of study for sociology. The link between sufficiency and biodiversity therefore requires an interdisciplinary perspective.

However, various factors make an interdisciplinary perspective difficult. According to Russels (2022) and MacLeod (2018), these factors include:

• different methodological approaches and technical terminology
• difficulties in reading and receiving texts from outside the discipline
• different conceptions of what the object of study is (or should be)

Moreover, according to Russels (2022), experts tend to focus on what they know.

An additional explanation for general statements about the link between biodiversity and sufficiency that affect both disciplinary and interdisciplinary research is provided by Leipold et al. (2024): They argue that underlying values and disciplinary paradigms influence collective science, constraining it and thus limiting its potential to contribute to inform and shape societal changes. They therefore propose a reflection on values and paradigms through a ‘narrative led dialogue’ (Leipold et al. 2024).