The diversity of species and genes in ecological communities affects the functioning of these communities. These ecological effects of biodiversity in turn are affected by both climate change through enhanced greenhouse gases, aerosols and loss of land cover, and biological diversity, causing a rapid loss of biodiversity and extinctions of species and local populations. The current rate of extinction is sometimes considered a mass extinction, with current species extinction rates on the order of 100 to 1000 times as high as in the past.
The two main areas where the effect of biodiversity on ecosystem function have been studied are the relationship between diversity and productivity, and the relationship between diversity and community stability. More biologically diverse communities appear to be more productive (in terms of biomass production) than are less diverse communities, and they appear to be more stable in the face of perturbations.
Also animals that inhabit an area may alter the surviving conditions by factors assimilated by climate.
In order to understand the effects that changes in biodiversity will have on ecosystem functioning, it is important to define some terms. Biodiversity is not easily defined, but may be thought of as the number and/or evenness of genes, species, and ecosystems in a region. This definition includes genetic diversity, or the diversity of genes within a species, species diversity, or the diversity of species within a habitat or region, and ecosystem diversity, or the diversity of habitats within a region.
Two things commonly measured in relation to changes in diversity are productivity and stability. Productivity is a measure of ecosystem function. It is generally measured by taking the total aboveground biomass of all plants in an area. Many assume that it can be used as a general indicator of ecosystem function and that total resource use and other indicators of ecosystem function are correlated with productivity.
Stability is much more difficult to define, but can be generally thought of in two ways. General stability of a population is a measure that assumes stability is higher if there is less of a chance of extinction. This kind of stability is generally measured by measuring the variability of aggregate community properties, like total biomass, over time. The other definition of stability is a measure of resilience and resistance, where an ecosystem that returns quickly to an equilibrium after a perturbation or resists invasion is thought of as more stable than one that does not.
The importance of stability in community ecology is clear. An unstable ecosystem will be more likely to lose species. Thus, if there is indeed a link between diversity and stability, it is likely that losses of diversity could feedback on themselves, causing even more losses of species. Productivity, on the other hand, has a less clear importance in community ecology. In managed areas like cropland, and in areas where animals are grown or caught, increasing productivity increases the economic success of the area and implies that the area has become more efficient, leading to possible long term resource sustainability. It is more difficult to find the importance of productivity in natural ecosystems.
Beyond the value biodiversity has in regulating and stabilizing ecosystem processes, there are direct economic consequences of losing diversity in certain ecosystems and in the world as a whole. Losing species means losing potential foods, medicines, industrial products, and tourism, all of which have a direct economic effect on peoples lives.
Field experiments to test the degree to which diversity affects community productivity have had variable results, but many long term studies in grassland ecosystems have found that diversity does indeed enhance the productivity of ecosystems. Additionally, evidence of this relationship has also been found in grassland microcosms. The differing results between studies may partially be attributable to their reliance on samples with equal species diversities rather than species diversities that mirror those observed in the environment. A 2006 experiment utilizing a realistic variation in species composition for its grassland samples found a positive correlation between increased diversity and increased production.
However, these studies have come to different conclusions as to whether the cause was due more to diversity or to species composition. Specifically, a diversity in the functional roles of the species may be a more important quality for predicting productivity than the diversity in species number. Recent mathematical models have highlighted the importance of ecological context in unraveling this problem. Some models have indicated the importance of disturbance rates and spatial heterogeneity of the environment, others have indicated that the time since disturbance and the habitat's carrying capacity can cause differing relationships. Each ecological context should yield not only a different relationship, but a different contribution to the relationship due to diversity and to composition. The current consensus holds at least that certain combinations of species provide increased community productivity.
In order to correctly identify the consequences of diversity on productivity and other ecosystem processes, many things must happen. First, it is imperative that scientists stop looking for a single relationship. It is obvious now from the models, the data, and the theory that there is no one overarching effect of diversity on productivity. Scientists must try to quantify the differences between composition effect and diversity effects, as many experiments never quantify the final realized species diversity (instead only counting numbers of species of seeds planted) and confound a sampling effect for facilitators (a compositional factor) with diversity effects.
Relative amounts of overyielding (or how much more a species grows when grown with other species than it does in monoculture) should be used rather than absolute amounts as relative overyielding can give clues as to the mechanism by which diversity is influencing productivity, however if experimental protocols are incomplete, one may be able to indicate the existence of a complementary or facilitative effect in the experiment, but not be able to recognize its cause. Experimenters should know what the goal of their experiment is, that is, whether it is meant to inform natural or managed ecosystems, as the sampling effect may only be a real effect of diversity in natural ecosystems (managed ecosystems are composed to maximize complementarity and facilitation regardless of species number). By knowing this, they should be able to choose spatial and temporal scales that are appropriate for their experiment. Lastly, to resolve the diversity-function debate, it is advisable that experiments be done with large amounts of spatial and resource heterogeneity and environmental fluctuation over time, as these types of experiments should be able to demonstrate the diversity-function relationship more easily.
Models have predicted that empirical relationships between temporal variation of community productivity and species diversity are indeed real, and that they almost have to be. Some temporal stability data can be almost completely explained by the averaging effect by constructing null models to test the data against. Competition, which causes negative covariances, only serves to strengthen these relationships.
This area is more contentious than the area of temporal stability, mostly because some have tried generalizing the findings of the temporal stability models and theory to stability in general. While the relationship between temporal variations in productivity and diversity has a mathematical cause, which will allow the relationship to be seen much more often than not, it is not the case with resistance/resilience stability. Some experimenters have seen a correlation between diversity and reduced invasibility, though many have also seen the opposite. The correlation between diversity and disease is also tenuous, though theory and data do seem to support it.
In order to more fully understand the effects of diversity on the temporal stability of ecosystems it is necessary to recognize that they are bound to occur. By constructing null models to test the data against (as in Doak et al. 1998) it becomes possible to find situations and ecological contexts where ecosystems become more or less stable than they should be. Finding these contexts would allow for mechanistic studies into why these ecosystems are more stable, which may allow for applications in conservation management.
More importantly more complete experiments into whether diverse ecosystems actually resist invasion and disease better than their less diverse equivalents as invasion and disease are two important factors that lead to species extinctions in the present day.
One major problem with both the diversity-productivity and diversity-stability debates discussed up to this point is that both focus on interactions at just a single trophic level. That is, they are concerned with only one level of the food web, namely plants. Other research, unconcerned with the effects of diversity, has demonstrated strong top-down forcing of ecosystems (see keystone species). There is very little actual data available regarding the effects of different food webs, but theory helps us in this area. First, if a food web in an ecosystem has a lot of weak interactions between different species, then it should have more stable populations and the community as a whole should be more stable. If upper levels of the web are more diverse, then there will be less biomass in the lower levels and if lower levels are more diverse they will better be able to resist consumption and be more stable in the face of consumption. Also, top-down forcing should be reduced in less diverse ecosystems because of the bias for species in higher trophic levels to go extinct first. Lastly, it has recently been shown that consumers can dramatically change the biodiversity-productivity-stability relationships that are implied by plants alone. Thus, it will be important in the future to incorporate food web theory into the future study of the effects of biodiversity. In addition this complexity will need to be addressed when designing biodiversity management plans.
Bacterivores are free-living, generally heterotrophic organisms, exclusively microscopic, which obtain energy and nutrients primarily or entirely from the consumption of bacteria. Many species of amoeba are bacterivores, as well as other types of protozoans. Commonly, all species of bacteria will be prey, but spores of some species, such as Clostridium perfringens, will never be prey, because of their cellular attributes.Biodiversity loss
Biodiversity loss is the extinction of species (plant or animal) worldwide, and also the local reduction or loss of species in a certain habitat.
The latter phenomenon can be temporary or permanent, depending on whether the environmental degradation that leads to the loss is reversible through ecological restoration / ecological resilience or effectively permanent (e.g. through land loss). Global extinction has so far been proven to be irreversible.
Even though permanent global species loss is a more dramatic phenomenon than regional changes in species composition, even minor changes from a healthy stable state can have dramatic influence on the food web and the food chain insofar as reductions in only one species can adversely affect the entire chain (coextinction), leading to an overall reduction in biodiversity, possible alternative stable states of an ecosystem notwithstanding. Ecological effects of biodiversity are usually counteracted by its loss. Reduced biodiversity in particular leads to reduced ecosystem services and eventually poses an immediate danger for food security, also for humankind.Copiotroph
A copiotroph is an organism found in environments rich in nutrients, particularly carbon. They are the opposite to oligotrophs, which survive in much lower carbon concentrations.
Copiotrophic organisms tend to grow in high organic substrate conditions. For example, copiotrophic organisms grow in Sewage lagoons. They grow in organic substrate conditions up to 100x higher than oligotrophs.Decomposer
Decomposers are organisms that break down dead or decaying organisms, and in doing so, they carry out the natural process of decomposition. Like herbivores and predators, decomposers are heterotrophic, meaning that they use organic substrates to get their energy, carbon and nutrients for growth and development. While the terms decomposer and detritivore are often interchangeably used, detritivores must ingest and digest dead matter via internal processes while decomposers can directly absorb nutrients through chemical and biological processes hence breaking down matter without ingesting it. Thus, invertebrates such as earthworms, woodlice, and sea cucumbers are technically detritivores, not decomposers, since they must ingest nutrients and are unable to absorb them externally.Depensation
In population dynamics, depensation is the effect on a population (such as a fish stock) whereby, due to certain causes, a decrease in the breeding population (mature individuals) leads to reduced production and survival of eggs or offspring. The causes may include predation levels rising per offspring (given the same level of overall predator pressure) and the allee effect, particularly the reduced likelihood of finding a mate.Dominance (ecology)
Ecological dominance is the degree to which a taxon is more numerous than its competitors in an ecological community, or makes up more of the biomass.
Most ecological communities are defined by their dominant species.
In many examples of wet woodland in western Europe, the dominant tree is alder (Alnus glutinosa).
In temperate bogs, the dominant vegetation is usually species of Sphagnum moss.
Tidal swamps in the tropics are usually dominated by species of mangrove (Rhizophoraceae)
Some sea floor communities are dominated by brittle stars.
Exposed rocky shorelines are dominated by sessile organisms such as barnacles and limpets.Ecological health
Ecological health is a term that has been used in relation to both human health and the condition of the environment.
In medicine, ecological health has been used to refer to multiple chemical sensitivity, which results from exposure to synthetic chemicals (pesticides, smoke, etc.) in the environment, hence the term ecological.
The term has also been used in medicine with respect to management of environmental factors (taxes, health insurance surcharges) that may reduce the risk of unhealthy behavior such as smoking.
As an urban planning term, ecological health refers to the "greenness" of cities, meaning composting, recycling, and energy efficiency.
With respect to broader environmental issues, ecological health has been defined as "the goal for the condition at a site that is cultivated for crops, managed for tree harvest, stocked for fish, urbanized, or otherwise intensively used."Ecological health differs from ecosystem health, the condition of ecosystems, which have particular structural and functional properties, and it differs from ecological integrity, which refers to environments with minimal human impact, although the term ecological health has also been used loosely in reference to a range of environmental issues. Human health, in its broadest sense, is recognized as having ecological foundations.The term health is intended to evoke human environmental health concerns, which are often closely related (but as a part of medicine not ecology). As with ecocide, that term assumes that ecosystems can be said to be alive (see also Gaia philosophy on this issue). While the term integrity or damage seems to take no position on this, it does assume that there is a definition of integrity that can be said to apply to ecosystems. The more political term ecological wisdom refers not only to recognition of a level of health, integrity or potential damage, but also, to a decision to do nothing (more) to harm that ecosystem or its dependents. An ecosystem has a good health if it is capable of self-restoration after suffering external disturbances. This is termed resilience.
Measures of broad ecological health, like measures of the more specific principle of biodiversity, tend to be specific to an ecoregion or even to an ecosystem. Measures that depend on biodiversity are valid indicators of ecological health as stability and productivity (good indicators of ecological health) are two ecological effects of biodiversity. Dependencies between species vary so much as to be difficult to express abstractly. However, there are a few universal symptoms of poor health or damage to system integrity:
The buildup of waste material and the proliferation of simpler life forms (bacteria, insects) that thrive on it - but no consequent population growth in those species that normally prey on them;
The loss of keystone species, often a top predator, causing smaller carnivores to proliferate, very often overstressing herbivore populations;
A higher rate of species mortality due to disease rather than predation, climate, or food scarcity;
The migration of whole species into or out of a region, contrary to established or historical patterns;
The proliferation of a bioinvader or even a monoculture where previously a more biodiverse species range existed.Some practices such as organic farming, sustainable forestry, natural landscaping, wild gardening or precision agriculture, sometimes combined into sustainable agriculture, are thought to improve or at least not to degrade ecological health, while still keeping land usable for human purposes. This is difficult to investigate as part of ecology, but is increasingly part of discourse on agricultural economics and conservation.
Ecotage is another tactic thought to be effective by some in protecting the health of ecosystems, but this is hotly disputed. In general, low confrontation and much attention to political virtues is thought to be important to maintaining ecological health, as it is far faster and simpler to destroy an ecosystem than protect it—thus wars on behalf of ecosystem integrity may simply lead to more rapid despoliation and loss due to competition.
Deforestation and the habitat destruction of deep-sea coral reef are two issues that prompt deep investigation of what makes for ecological health, and fuels a great many debates. The role of clearcuts, plantations, and trawler nets is often portrayed as negative in the extreme, held akin to the role of weapons on human life. (See Human impact on the environment.)Energy Systems Language
The Energy Systems Language, also referred to as Energese, Energy Circuit Language, or Generic Systems Symbols, was developed by the ecologist Howard T. Odum and colleagues in the 1950s during studies of the tropical forests funded by the United States Atomic Energy Commission. They are used to compose energy flow diagrams in the field of systems ecology.Feeding frenzy
In ecology, a feeding frenzy occurs when predators are overwhelmed by the amount of prey available. For example, a large school of fish can cause nearby sharks, such as the lemon shark, to enter into a feeding frenzy. This can cause the sharks to go wild, biting anything that moves, including each other or anything else within biting range. Another functional explanation for feeding frenzy is competition amongst predators. This term is most often used when referring to sharks or piranhas. It has also been used as a term within journalism.Lithoautotroph
A lithoautotroph or chemolithoautotroph is a microbe which derives energy from reduced compounds of mineral origin. Lithoautotrophs are a type of lithotrophs with autotrophic metabolic pathways. Lithoautotrophs are exclusively microbes; macrofauna do not possess the capability to use mineral sources of energy. Most lithoautotrophs belong to the domain Bacteria, while some belong to the domain Archaea. For lithoautotrophic bacteria, only inorganic molecules can be used as energy sources. The term "Lithotroph" is from Greek lithos (λίθος) meaning "rock" and trōphos (τροφοσ) meaning "consumer"; literally, it may be read "eaters of rock". Many lithoautotrophs are extremophiles, but this is not universally so.
Lithoautotrophs are extremely specific in using their energy source. Thus, despite the diversity in using inorganic molecules in order to obtain energy that lithoautotrophs exhibit as a group, one particular lithoautotroph would use only one type of inorganic molecule to get its energy.Mesotrophic soil
Mesotrophic soils are soils with a moderate inherent fertility. An indicator of soil fertility is its base status, which is expressed as a ratio relating the major nutrient cations (calcium, magnesium, potassium and sodium) found there to the soil's clay percentage. This is commonly expressed in hundredths of a mole of cations per kilogram of clay, i.e. cmol (+) kg−1 clay.Microecosystem
Microecosystems can exist in locations which are precisely defined by critical environmental factors within small or tiny spaces.
Such factors may include temperature, pH, chemical milieu, nutrient supply, presence of symbionts or solid substrates, gaseous atmosphere (aerobic or anaerobic) etc.Mycotroph
A mycotroph is a plant that gets all or part of its carbon, water, or nutrient supply through symbiotic association with fungi. The term can refer to plants that engage in either of two distinct symbioses with fungi:
Many mycotrophs have a mutualistic association with fungi in any of several forms of mycorrhiza. The majority of plant species are mycotrophic in this sense. Examples include Burmanniaceae.
Some mycotrophs are parasitic upon fungi in an association known as myco-heterotrophy.Organotroph
An organotroph is an organism that obtains hydrogen or electrons from organic substrates. This term is used in microbiology to classify and describe organisms based on how they obtain electrons for their respiration processes. Some organotrophs such as animals and many bacteria, are also heterotrophs. Organotrophs can be either anaerobic or aerobic.
Antonym: Lithotroph, Adjective: Organotrophic.Planktivore
A planktivore is an aquatic organism that feeds on planktonic food, including zooplankton and phytoplankton.Population cycle
A population cycle in zoology is a phenomenon where populations rise and fall over a predictable period of time. There are some species where population numbers have reasonably predictable patterns of change although the full reasons for population cycles is one of the major unsolved ecological problems. There are a number of factors which influence population change such as availability of food, predators, diseases and climate.Recruitment (biology)
In biology, especially marine biology, recruitment occurs when a juvenile organism joins a population, whether by birth or immigration, usually at a stage whereby the organisms are settled and able to be detected by an observer.There are two types of recruitment: closed and open.In the study of fisheries, recruitment is "the number of fish surviving to enter the fishery or to some life history stage such as settlement or maturity".Relative abundance distribution
In the field of ecology, the relative abundance distribution (RAD) or species abundance distribution describes the relationship between the number of species observed in a field study as a function of their observed abundance. The graphs obtained in this manner are typically fitted to a Zipf–Mandelbrot law, the exponent of which serves as an index of biodiversity in the ecosystem under study.Species homogeneity
In ecology, species homogeneity is a lack of biodiversity. Species richness is the fundamental unit in which to assess the homogeneity of an environment. Therefore, any reduction in species richness, especially endemic species, could be argued as advocating the production of a homogenous environment.