The ecology ( ancient Greek οἶκος oikos 'house', 'household' and λόγος logos 'doctrine'; thus "doctrine of the household") is according to its original definition a scientific sub-discipline of biology , which the relationships between living beings (organisms) and their explored inanimate environment . In the second half of the 20th century, the term was increasingly used to denote the overall environmental situation, but it also became more diffuse overall. The adjective “ecological” was mostly used colloquially as an expression for an attitude or an act that is careful with environmental resources .
Origin, definition and variety of meanings of ecology
As the founder of basic ecological research, Charles Darwin (ecology of earthworms, interaction between ecology and evolution), Karl August Möbius (marine animals), Johannes Eugenius Bülow Warming (plant ecology and plant geography), Arthur George Tansley (ecosystem aspects) and August Thienemann (ecology the inland waters). Justus von Liebig (agro-nutrient ecology ) and Ellen Richards (hygiene) should be mentioned as examples from the applied ecological research direction . The central works of the aforementioned appeared between around 1840 (Liebig) and 1940.
Definitions of the scientific term ecology were first given in the years 1866 to 1869 (with slight changes in the wording) by Ernst Haeckel , a leading German zoologist at the time and an advocate of Darwin's theory of descent . Haeckel himself did not conduct research in the field of ecology, but defined the term as a study of the interactions between types of organisms. In his last definition, he understood it to include the entire budget of nature, a definition that comes close to our current broad understanding of ecology:
“By ecology we mean the entire science of the relationships between the organism and the surrounding outside world, where we can count all“ conditions of existence ”in the broader sense. These are partly organic, partly inorganic in nature; Both these and those are, as we have shown before, of the greatest importance for the form of organisms, because they force them to adapt to them. "
However, the term did not establish itself in biology until the end of the 19th century and its definition was modified , sometimes more narrowly, sometimes very broadly.
Instead of ecology, in the 18th and 19th centuries people often spoke of economics (as in Goethe), a term that was formerly used in the (southern) German-speaking area for farms and is still sometimes used in the Anglo-Saxon area for ecological processes . The term “biology” in the sense of “ecology” was and is used in various ways, for example in terms such as “flower biology”. Another parallel term sometimes used in Romance languages was mesology . The term bioecology is often used by geoscientists and landscape ecologists to distinguish the orientation that emerged from biology from a more geoscientifically oriented geoecology . However, the latter is also understood differently, either more in the sense of the physical-geographical landscape ecology or in the sense of an environmental (natural) science focused on the material dynamics .
Right from the start, in ecological research and teaching, one could distinguish between a basic orientation, sometimes also called theoretical ecology , and an applied ecology . The latter focused strongly on problems in forestry, agriculture, water pollution control and hygiene for humans and animals. The basic research saw their main goal is to understand how the interactions in nature, having been the first to point out that a lot of basic findings also have application references directly or indirectly.
Research approaches in ecology
At the beginning of an ecological investigation there is often a statistical-descriptive inventory, in which the living beings or other ecological parameters of interest are recorded and usually the corresponding environment is characterized at the same time. By comparing findings from several areas and regions or periods of time, patterns can be recognized, for example recurring species communities whose representatives obviously have similar demands on the environment or which often occur together (associated) for other reasons. Such approaches lead to classification systems of the environment, for example the subdivisions into vegetation zones or plant sociological units, which are often used for a brief characterization of animal biotopes (habitats). Descriptive descriptions and classifications are often an important first step in the formation of hypotheses.
In ecology, causal analysis questions often arise from observations in natural or cultural landscapes or from intensive observations of individual individuals or populations. Correlations between the occurrence or frequency of a species or a genotype on the one hand and abiotic environmental factors on the other hand can provide information on the physiological-ecological demands ( resource requirements ) of species. Biotope and food requirements, predatory and parasitic opponents as well as space or food competitors can be recognized or suspected. The type of suspected interaction can be formulated in the form of a hypothesis, which is either corroborated or falsified by further observations, for example in other regions, or by targeted experiments in the laboratory or in the field . Field experiments can, for example, be carried out in such a way that certain organisms are prevented from accessing an observation area. For example, rabbits and deer can be kept away from a meadow by fences, and small fish in the water body that would otherwise eat the zooplankton using net structures. From the system behavior of the environment, from which an important trophic component has been withdrawn in each case , more precise hypotheses about the interaction in the system can be developed, which may be subjected to a new test for refinement.
The inventory of methods includes, on the one hand, genuinely ecological methods (e.g. detection, trapping and collection methods, statistical methods for evaluating certain distribution patterns), and, on the other hand, methods from neighboring disciplines, including soil science , meteorology , limnology , genetics and, always, statistics . Applied Ecological Research, especially also Social-Ecological Research, next to used methods inventories, which in the social sciences , in economics , sociology , anthropology and psychology has been developed. Socio-ecological analyzes refer to the material and immaterial relationships between nature and human society; In this context, an attempt is often made to find solutions for sustainability programs. Approaches to uniting and discussing aspects of the various disciplines mentioned can be found, for example, in individual research projects .
Practical ecological questions are also very central in nature and species protection , when evaluating the economic importance of ecosystems ( ecosystem services ) as well as in agriculture , forestry and fisheries science . Ecological monitoring , which records, categorizes and catalogs certain organisms, substances or state variables of the environment as a potential basis for measures, is highly applied and important in environmental protection . Special and partially standardized procedures have been developed for all of these areas, which often enable a direct comparison with planning measures and legal requirements.
Traditional subdivision of ecology
In the 20th century, the teaching and research subject of (biological) ecology in the German-speaking area was traditionally divided into the three areas of autecology, population ecology and synecology (the ecology of communities ). The ecosystem theory developed from the third sub-area. Special areas that were added later included the analysis of biological and ecological diversity or research into the relationship between biological and structural diversity and the stability / resistance of the ecological system to disturbances. From a botanical point of view, an ecologically oriented plant-sociological approach (founded by Josias Braun-Blanquet ) was pursued - albeit almost exclusively in continental Europe - which led to a complex classification of plant-sociological units as well as lists of pointer plants according to the then (still little of neophytes and climate change) vegetation of Central Europe was developed.
Methodological and content-related difficulties of ecological research lie in the high complexity of most ecological systems as well as their dynamics and interaction with other ecosystems via material flows and the exchange of organisms, which are strongly based on stochastic principles. In addition, there are always unpredictable influences from new types of environmental pollution, from eutrophication and climate change to immigration and the establishment of invasive species from other regions and continents. This also hindered the development of reliable and stable classification systems of the environment from the beginning, which were pursued for much of the 20th century, most impressively in plant sociology , but even with imitative experiments in animal ecology. The specific and open system properties and dependencies on external rivers make it difficult or even impossible to make predictions about future developments, for example population sizes of endangered animal species.
Autecology: ecology of species
Autecology was coined as a term in 1902 by the German botanist Carl Schroeter , who teaches in Switzerland, and was initially understood as an antithesis to synecology. Autecology deals with the interactions between individuals and environmental factors. These environmental "factors", which can be better characterized by system analysis as influencing variables or control variables, include on the one hand abiotic influencing variables such as light intensity, soil fertility and atmospheric pressure, in the aquatic system among other things the depth-dependent light intensity and quality, the oxygen concentration and ion composition in the water. On the other hand, they also include biotic influencing factors, such as food quality and quantity or the direct interrelationship with parasitic or symbiotic species, and in animals also behavioral- ecological aspects of dealing with other species.
A basic concept of this approach is that living beings are generally only viable within certain tolerance ranges of the individual factors, insofar as these can be quantified. In reality, the situation is complex in that the various influencing variables interact mutually, and the individuals also have a certain, albeit limited, physiological ability to adjust to suboptimal conditions and in that many tolerance limits also depend on the biological “competitive situation” the species are in see the respective system exposed. Finally, in the course of longer periods of time, a certain shift in the tolerance range due to genetic changes, for example changes in allele frequency, is to be expected. The specific demands or tolerances of a species with regard to certain factor values as well as the interactions between the influencing variables are described and analyzed by the concept of the ecological niche and also applied in the context of evolutionary biological interpretations.
The term auto-ecology is only rarely used in modern teaching and research practice due to these diverse interrelationships, rather the term physiological ecology or as an adjective also ecophysiological .
Population ecology: ecology of populations
In population ecology (also called "demecology" in German-speaking countries, based on Schwerdtfeger 1968) quantitative aspects within a population or reproductive unit are described and analyzed. Accordingly, a distinction was previously made between a descriptive (static) population analysis and a dynamic approach, which examined aspects such as population growth and demographic changes and was accordingly referred to as “ population dynamics ”. Earlier, and above all in applied entomology, the term “mass change” was also common. In population dynamics, populations with a complex gender and age composition are described and analyzed using demographic methods in order to identify trends, fluctuations and tendencies. The underlying models were originally largely deterministic models, later increasingly stochastic models. More recently, the changes over time in the genetic basis of the populations and in the confrontation with other populations have also come into focus.
If population genetic aspects such as allele or genotype frequencies are taken into account , one often speaks of population biology . Long-term changes as a result of evolutionary processes no longer belong in the traditional area of population ecology, but in the resulting population biology, evolutionary ecology or even evolutionary biology .
Synecology: ecology of living communities
Synecology examines natural communities from an ecological perspective. Like autecology, the term was coined by Carl Schroeter in 1902 and formerly also comprised the part that corresponds to today's population ecology. However, the term is no longer used frequently and has given way to the term and concept of ecosystem analysis, which from the beginning also focused on the energy flow and material cycle in addition to the community .
The task of classical synecology is the analysis of the interspecific interactions in the community ( biocenosis ) and their dependencies on the " biotope ", i. H. all structural relationships and influencing variables outside the organism community under consideration. Biotope and biocenosis formed the ecosystem in this model-like simplification, although this comparison does not exist in reality, since the biotope is also changed by the organism community itself, for example in that earthworms and other burrowing and rooting organisms influence the local soil properties. Central traditional research topics include interactions as a result of competition , predation -prey relationships (predation in the narrower sense), herbivory, host-parasite relationships and cooperative relationships, which can be summarized as mutualism relationships. In many cases, mathematical and statistical methods are used to describe and model communities, in applied research also models for (more or less reliable) forecasts.
A widespread approach for the analysis of complex communities is that the dynamics of biocenoses is investigated on comparatively simple systems, often consisting of only two species, through observation, experiment (also in long-term studies ) and modeling. The underlying understanding is that complex communities can be made more manageable by reducing them to partial aspects and can be understood as examples. So the concept of trophic levels ( producers , consumers and destructors ) arose from this, even if this again represents a model-like simplification in the overall food web itself.
Newer focus areas
Naturally, ecological problems can be approached differently. An unorthodox question, perhaps caused by modern methods available or as a result of new types of environmental pollution, can become the starting point for a new focus with its own name, problem, analysis and interpretation. The following list of more recent approaches is not complete and will naturally change. However, it does reflect the diversity of approaches, with overlaps also occurring.
- As a Chemical Ecology is known from about the 1960s / 70s, two different approaches, on the one hand the study of the occurrence and distribution of chemical substances in the ecosystems. This also included the environmental chemicals that appeared in large numbers and quantities from the middle of the 20th century, of which decomposition and conversion products were soon to be found in the environment. On the other hand, chemical ecology describes the study of the role of chemical signals in the interrelationships of organisms. This approach resulted in some practical applications, such as the development of methods for biological pest control. In some cases, these two directions also merge, for example when the presence of new types of environmental chemicals disrupts the chemical communication of living beings.
- The Evolutionary Ecology investigates issues in the border area of ecology and evolution. It established itself around the 1960s to 1970s, but experienced a kind of renaissance two decades later with the introduction of molecular genetic analyzes. The term was and is often used in the field of behavior analysis, for example to investigate complex pairing systems and the analysis of gene transmission in the course of the succession of generations. In a broader sense, however, evolutionary ecology encompasses all aspects that contain evolutionary components in the analysis or interpretation, because many ecological systems are also genetically evolving systems.
- As molecular ecology refers to approaches and methods, environmental issues using molecular genetic basis to investigate. The orientation and designation became established around 1990, after the PCR technology in particular greatly simplified the use of molecular methods in ecology. This approach acquired a special meaning for questions from population ecology and biology. Genetic sequences are often used as markers in order to be able to make statements about population differentiation on a genetic basis, about species hybridization and genetic diversity in a population or an ecosystem. The available or interesting DNA components in the system section are analyzed and assigned. This also includes the use of DNA barcoding to identify species.
- The biological diversity may refer, depending on the orientation of the diversity of the genes of the species and ecosystems. The interaction between climate change and biodiversity change has also become a focus of research. The concept of biodiversity was introduced in the last 10 years of the 20th century, but did not spread to us until the first decade of the 21st century. As far as genomes and gene sequences are at the center of consideration, the terms environmental genomics, metagenomics or biodiversity genomics are also occasionally used ; These orientations only became possible on a larger scale with the time-saving and inexpensive genome analysis in the second decade of the 21st century.
- Macroecology is an approach and orientation that emerged from around 1990, but did not become more widespread until the 21st century. Here, patterns and mechanisms are researched that can be observed over larger regions and partly also over time for the examined taxonomic-ecological units (species, characteristics, species communities). It partially overlaps with other ecological approaches and disciplines.
Further areas of ecology
Numerous other focus areas have developed, some of which have reached their peak or whose current research content has switched to other ecological disciplines. Many branches of research that used to be carried out within the so-called animal ecology, hydrobiology or microbial ecology are now classified under headings such as evolutionary ecology, ecosystem analysis or molecular ecology. The reasons for this can lie with the scientists themselves, who do not want to see themselves operating in an “old-fashioned” research area. Sometimes, however, they also lie in the research funding institutions, which tend to support approaches and content that appear to be novel thematically, conceptually and methodologically, and which are used by the applying scientists and institutions as a basis.
- The classification according to groups of organisms traditionally allowed a distinction to be made between animal ecology, plant ecology and microbe ecology, which were often dealt with in separate textbooks.
- The breakdown according to major habitats on earth allowed a distinction to be made between marine ecology , freshwater ecology (hydrobiology or limnology ), terrestrial ecology (continental ecology, very rarely historically also called epirology). In a finer subdivision, one also speaks of forest ecology , river ecology or also cave ecology and groundwater ecology . The specific interrelationship between flowers and insects or other pollinators is examined in the context of flower ecology (traditionally also called flower biology). The discipline of aeroecology is dedicated to the airspace .
- The term theoretical ecology is sometimes used synonymously for basic research in ecology, sometimes also for the elaboration of mathematical-formulaic or physico-chemical principles of ecology (predator-prey interaction, energy flow, material cycles, formal population genetics, etc.). From this field, among other things, many ecological models have developed that generally play a major role nowadays, even if outside of science they are often confused with prognoses .
- Applied ecology sees itself (in contrast to theoretical or basic ecology) as tailored directly to human needs. It traditionally includes forest ecology, pest control or the ecology of bees and other important livestock and plants. In principle, the ecology of water pollution control also belongs here, but is often listed as an independent terminology or under hydrobiology (also technical hydrobiology).
- When human ecology is called the effect of ecological interactions between humanity and its environment, the content-orientations can be either rather scientific, technical, planning or social studies. The term human ecology can either refer more to the pre-civilizational development of mankind (ecology of indigenous or earlier peoples) or to modern mankind. The content of this branch has been partially incorporated into the term social ecology (and related terms) since the end of the 20th century .
- Social ecology or socio-ecological research are the names of predominantly social science-oriented questions and research fields in which primarily aspects of sustainability or research content of other direct relevance to today's human society are analyzed or taken into account, for example ecological economics . The extent to which scientific research components are taken into account and incorporated depends on the respective institution or social science "school".
- The civilization ecology deals with the effects of technical civilization on organisms and habitats and environmental problems and possible solutions for their control. It is often strongly oriented towards social science, but the term, like the term human ecology, is not (no longer) as widespread as social ecology.
- The Behavioral Ecology examines interactions of animal behavior and environmental factors, now often also using molecular methods. Traditionally, human behavior is not in the foreground, but is often taken into account, also in cooperation with environmental psychology and related areas.
- The Environmental Sciences (in the ecological sense) investigated the interaction of abiotic subsystems (eg. As soil, seepage and groundwater) between themselves and with biotic subsystems (. Eg roots, earthworms). It is considered, in various forms, as a branch of science and teaching at the interface of ecology, environmental chemistry , geography and sometimes also the social sciences , often also integrating aspects of soil science, hydrology or remote sensing .
- The Soil Ecology examines the ecological relationships of soil-dwelling organisms (earthworms, soil mites, fungi), but often highly applied nature towards agriculture, where traditionally very soil fertility attention is paid.
- Urban or urban ecology is dedicated to the rapidly increasing global density of densely populated urban regions, their specific ecological conditions and their fauna and flora that live in parks and stone cracks, in house gardens and on ruderal locations. The ecological conditions of people living or working in urban regions can also be the subject of urban ecology. The counterpart on the agriculturally used surrounding area is often called agroecology .
- The paleoecology studied the ecological conditions and relationships of yesteryear and earth periods, usually based on rocks (often former sedimentary deposits ), chemical ingredients and fossil remains . Recent analogue examples can be used to interpret some of the findings .
- The Landscape Ecology is directed to the spatial characteristics of ecological relationships and control circuits. She researches the interaction between biodiversity and geodiversity at the level of the resulting landscape diversity .
Scientific theoretical discussions about ecological systems
From the beginning of the 20th century, the philosophical and epistemological side discussed how ecological systems should be seen, assessed and examined. Should they be seen and analyzed primarily as holistic systems, as it were as highly organized superorganisms, whose species all have specific functions and where only their harmonious overall play ensures the functioning of the ecosystem. The observed or apparent homeostatic stabilizations would then result, as it were, from the system behavior. Or are ecosystems to be seen and analyzed as more or less random aggregations of populations and species that fit into the overall system. This contrast also affected the question of whether ecosystems are approaching an “ideal state”, a “climax community”, which can then be given a special name, or whether they are generally to be seen as stochastically occurring transition systems. These different concepts of ecological organization and the appropriate research approaches, expressed philosophically also about the ontological status of ecological communities, have been debated in a number of controversies:
- Since the beginning of the 20th century there has been speculation about whether ecological systems should be viewed holistically, comparable to an organism, or whether the system should be understood more in terms of its individual components. The term holism was thrown into the debate from 1926 onwards in particular by the South African statesman and general Jan Smuts . In contrast, there were the representatives of a concept of individualism, strongly represented by the American botanist and ecologist HA Gleason ,
- The strong classificatory approaches in ecology in the first half of the 20th century, as practiced specifically by Germany's plant-sociological orientation, were contrasted with a continuum or gradient concept. The central question of the debate was whether we actually have definable communities in front of us or rather continuous transitions in the sense of gradients (an approach that dominated above all in American research, where consequently no plant-sociological systems were defined Superorganism concept for ecosystems adopted and examined primarily functionally. They are seen as open systems which, especially today, form new and often temporary communities all over the world with newly emerging invasive species and changing other environmental conditions.
- Another debate sparked the Gaia hypothesis by James Lovelock and Lynn Margulis from the mid-1960s. The two authors argued - and later tried to underpin their hypotheses with modeling - that the earth as a whole and throughout the history of the earth behaves like a self-regulating system and thus also shows a high level of self-organization that seeks to maintain optimal conditions for earthly organisms. Their concept and model later also included the changes in the earth's material balance from the earliest geological times to the future (with the cessation of all life). These models with the postulate impressive self-regulation of the earth found enthusiastic followers in many non-scientific circles. On the scientific level, the system-theoretical approach was received positively, but the derivations and explanations were often interpreted differently than by a global, self-sustaining optimal state.
- Another critical discussion concerned the "ecological balance", which is widely propagated in public and presented as exemplary for human activity, and the question of whether it is real at all or just a fixed idea, perhaps due to the fact that we ourselves only oversee a very limited period of time and long-term changes seem constant to us. This discussion can be described as the equilibrium-imbalance debate, which was also critically examined and discussed mathematically on the basis of the system behavior of complex systems. In the meantime, ecologists themselves rarely speak of an “ecological balance”, but rather emphasize the dynamic and fragile aspects of natural population and ecosystems.
In philosophical discussions, ecological systems and the research subject of ecology are now discussed less in an epistemological context and more in the context of ethics , for example with regard to what (also immaterial) "value" intact ecological systems have for humanity or what we ecological systems or for but must protect biological diversity (biodiversity), whether “for nature” or “for us humans”. Such questions and developments have also arisen to a large extent in connection with the transformation of the term ecology (see following section).
Politicization and popularization of the concept of ecology
Until the end of the 1960s, the term ecology was little known and the corresponding branch of research was also regarded within the biological sciences as a rather marginal, traditional and outdated or even historical approach, which in its reputation was located well behind the then modern physiological and biochemical laboratory methods. The so-called International Biological Program (IBP) , decided by UNESCO in 1964 , which was actually implemented from 1967 to 1974 and through which approaches of large-scale research were transferred to ecology for the first time , contributed to a certain dissemination and popularization of ecological approaches and research approaches. However, this was initially only really noticed in the area of ecological science and the institutions involved. In this context, several large-scale ecosystem analysis projects were pursued worldwide, including the Solling project in Germany . The Man and the Biosphere program , which started in 1971 , also developed research and awareness far beyond the narrow scientific framework of biology and has meanwhile led to more than 670 biosphere reserves in around 120 countries. To 1970, established de facto , the terms environment and environmental protection in the German politics and everyday language. However, from now on, ecology and "ecological" increasingly meant a sustainable use of nature that was gentle on resources and the intact environment, and also a "natural" lifestyle.
In the US, and later also here, Rachel Carson became known for her warning of a "silent spring" (as her book title from 1962) referred to the pesticide problem and endangerment of the bird world. This ultimately led to an extensive ban on the use of DDT and other persistent and accumulating environmental toxins . Also in the 1960s, the voices for effective water protection in Europe became louder and louder, because heavy metal and salt loads, eutrophication and oxygen depletion had led to a drastic change in the organism world with algal blooms and fish deaths in many rivers and lakes and were at the same time, also about the Contamination of the groundwater, a health problem for humans and livestock. Sewage treatment plants with sometimes a so-called third purification stage (for the precipitation of phosphates and other inorganic substances ), ring lines around lakes and a drastic restriction of the application of fertilizers into the environment were now required and implemented by law in the course of the following decades. In the area of the new federal states and also in many former Eastern Bloc states , the corresponding remedial measures were mainly implemented effectively only in the 1990s.
From the 1970s onwards, ecological findings, which, in addition to the pollution and hazard potential, also addressed the finite nature of earthly resources, were increasingly related to and partially transferred to social issues. Important stimuli were the study Limits to Growth (1972) published by the Club of Rome and the report to the US President Global 2000 from 1980.
The concept of a now more normative interpretation of “ecology” soon made it the leading science of an ecological movement that also appeared actively in Germany in the 1970s and 1980s. As the word ecology found its way into everyday vernacular, its meaning and the originally value-neutral natural science discipline had developed into a norm that was perceived as positive and a goal to be achieved, so that ecological almost synonymous with environmentally friendly, clean, considerate or too good and was felt correctly. Almost at the same time, the short form “Öko / öko”, with a similar meaning also “organic”, in combination with terms that could be associated with pollutant-free and resource-saving forms of economy, e.g. B. eco-farmers , eco-settlement , eco-energy or green electricity , eco-fashion, “eco-fair” (organically grown and fairly traded). From now on, the short form eco was also used specifically for marketing purposes. From around the turn of the millennium, the term sustainability (which in principle had already existed for a long time) became a largely synonymous, albeit contemporary term for "ecological", just and good, and from the beginning of the 21st century was almost inflationary on the environment, Society and economy applied.
Selection of textbooks
- M. Begon, WH Howarth, CR Townsend: Ecology. 3. Edition. Springer Spectrum, Berlin 2016, ISBN 978-3-662-49905-4 .
- Hartmut Bick: Basics of Ecology. 3. Edition. Gustav Fischer, Stuttgart 1998, ISBN 3-437-25910-5 .
- Wolfgang Nentwig , S. Bacher, R. Brandl: Ecology compact. 3. Edition. Spectrum Akademischer Verlag, Heidelberg 2011, ISBN 978-3-8274-1876-0 .
- Eugene P. Odum : Ecology. Basics - locations - applications. 3. Edition. Thieme, Stuttgart 1998, ISBN 3-13-382303-5 .
- Matthias Schäfer: Dictionary of Ecology. 5th edition. Spektrum Akademischer Verlag, Heidelberg 2011, ISBN 978-3-8274-0167-0 .
- Thomas M. Smith, Robert L. Smith: Ecology. 6th edition. Pearson Studies, Munich 2009, ISBN 978-3-8273-7313-7 .
- Bruno Streit : Ecology. A short textbook. G. Thieme, Stuttgart 1980, ISBN 3-13-583501-4 .
- Ludwig Trepl : General ecology. Volume 1: Organism and Environment. Lang, Frankfurt am Main 2005; Volume 2: Population. Lang, Frankfurt am Main 2007.
- Rüdiger Wittig , Bruno Streit : Ecology. Ulmer, Stuttgart 2004, ISBN 3-8252-2542-9 .
- Neil A. Campbell, Jane B. Reece, Robert L. Smith, Thomas M. Smith: Biology for High School - Topic Volume Ecology . Pearson Studies, 2010, ISBN 978-3-86894-906-3 .
- Ernst Haeckel : General Morphology of Organisms. General principles of the organic science of forms, mechanically founded by the descent theory reformed by Charles Darwin. Volume 2, Berlin 1866, p. 286. ( Download from the Biodiversity Heritage Library)
- Johann Wolfgang von Goethe: The metamorphosis of insects, especially butterflies, as well as their other properties and economy. Weimar 1798.
- z. B. Robert E. Ricklefs: Ecology: The Economy of Nature. 7th edition. MacMillan Learning, 2014, ISBN 978-1-4292-4995-9 .
- Website of the focus on social-ecological research at the Federal Ministry of Education and Research
- Sahotra Sarkar: Ecology . In: Stanford Encyclopedia of Philosophy. December 23, 2005.
- Fritz Schwerdtfeger : Ecology of the animals. A teaching and manual in 3 parts . Volume 2: Demecology. Structure and dynamics of animal populations . 1968 and subsequent editions
- B. Streit, T. Städler, CM Lively (eds.): Evolutionary Ecology of Freshwater Animals. Concepts and case studies. (= Experientia Supplementum Series. (EXS). Vol. 82). Birkhäuser, Basel / Boston 1997, ISBN 3-7643-5694-4 .
- B. Schierwater, B. Streit, GP Wagner, R. deSalle (Eds.): Molecular Ecology and Evolution: Approaches and applications. Birkhäuser, Basel / Boston / Berlin 1994, ISBN 3-7643-2942-4 .
- D. Steinke, N. Brede: Taxonomy of the 21st Century - DNA Barcoding. In: Biology in Our Time. 36, 2006, pp. 40-46.
- Bruno Streit, Katrin Böhning-Gaese, Volker Mosbrugger: Biodiversity and Climate: Change in full swing! In: Biology in Our Time. 4/2011, pp. 248-255.
- Christiane Griebler, Friederike Mösslacher: Groundwater Ecology. UTB, Stuttgart 2003, ISBN 3-8252-2111-3 .
- Holism and Evolution. Macmillan, London 1926. (German: Die holistische Welt. With a foreword by the author to the German edition and a foreword by Adolf Meyer, edited and translated by Helmut Minkowski. Metzner, Berlin 1938)
- RP Mcintosh: HA Gleason's 'individualistic concept' and theory of animal communities: a continuing controversy. In: Biological Reviews. 60 (2), 1995, pp. 317-357; Thomas Kirchhoff: System conceptions and biological theories . Technical University of Munich, Freising 2007, pp. 77–116.
- RH Whittaker: Gradient analysis of vegetation. In: Biological Reviews. 42 (2), 1967, pp. 207-264, here: 209.
- Daniel B. Botkin: Discordant harmonies: a new ecology for the twenty-first century . Oxford University Press, Oxford 1990; Klaus Rohde: Nonequilibrium ecology . Cambridge University Press, Cambridge 2005; Josef H. Reichholf: Stable imbalances. The ecology of the future . Suhrkamp, Frankfurt am Main 2008.
- Ueli Haefeli-Waser: Ecology. In: Historical Lexicon of Switzerland .
- Sahotra Sarkar: Ecology . In: Stanford Encyclopedia of Philosophy. December 23, 2005.
- Link collection ecology in the virtual library of biology (vifabio)
- Basic terms of ecology (German, English, Spanish, Catalan)