Let's imagine a line representing a continuum or a "straight horizon". Now let us have some up and down lines in that graph, relative to that first straight line.
Surprisingly, both can be examples of stability or equilibrium. More often than not, the up and down lines are what maintains the equilibrium. At some point in the "lifespan" of a graph, a state of non-variation and "graph silence" is reached, even if temporarily. It depends on how closely you zoom in, or out of it.
On Earth, variance on the equilibrium line is also driven by the push-and-pull evolutionary processes. These are affected by the predator-prey (biodiversity) interactions. The stability of an ecosystem on Earth is the result of an ongoing feedback loop that follows patterns. Stability in nature very rarely follows a straight line.
Let's analyse the concept of environmental stability and its biota below.
Biota and the Environment (Meaning)
The environment encompasses all elements that surround us.
Biota, or biodiversity, refers to all life in an ecosystem. This includes the Bacteria, Archaea, and Eukarya domains. Basically, everything from microorganisms to large mammals.
Biota are the backbone of environmental stability, maintaining the functioning of ecosystems and keeping services like clean water and air "running". Biotic matter also releases nutrients, which can then be decomposed and used by other organisms.
During their lifespan, some species help fixate chemical compounds such as nitrogen, or help filtrate particulates from water. Microorganisms called diazotrophs, for example, naturally fixate nitrogen in soils by converting it into ammonia (NH3) or other compounds like nitrites and nitrates. Plants like white clover "house" such bacteria in their roots.
When thinking about environmental stability, it is important to consider homeostasis. If you have a look at the previous lesson's Key takeaway (The Living Environment) you will probably get the gist of this chapter pretty quickly: "We are part of a distinct global ecosystem that is constantly trying to achieve homeostasis."
Let's dive further into a definition by S. K. Ernest (2008):
Homeostasis is the ability of ecological systems to maintain stable system properties despite perturbations. Properties of systems reflect the system as a whole and are not solely determined by the identity of the species in the system.
But why do we need to know this?
It's because the environment and the biota define each other. Below, you will see the most important factors determining these interactions that maintain stable living conditions.
Environmental Stability Definition
A stable and resilient ecosystem structure is less affected by the changing numbers of one species because there are other species that can fulfil the same or a similar role.
Environmental or ecosystem stability refers to the capacity to remain relatively unchanged in function and structure over large periods of time and despite perturbations.
In an unstable ecosystem, there is a singular link in a process (e.g. x can only be pollinated by y) which makes that type of interaction (e.g. pollination) vulnerable to change because nothing else can replace it.
Perturbations can occur due to the change of seasons, ageing of organisms, migrations, or anthropogenic activities. Perturbations can be both biotic and abiotic.
Some changes may occur due to ecological succession.
Ecological Succession
Ecological succession is a natural process that happens when one ecosystem type is slowly colonized by different species. Succeeding species usually replace the species that had arrived first, called pioneer species. On Earth, this process is cyclical and helps balance ecosystems. We can distinguish between primary and secondary succession.
Primary succession happens when life is eliminated by abiotic factors such as volcanism or glaciation, due to which previously biotic environments cannot sustain the growth of organisms. It starts with barren environments.
Secondary succession refers to a partial extinction event where the environment is not entirely barren and can still host some life. Examples of events that generate this type of succession include wildfires and floods.
Hundreds of years or more can pass for one of these processes to complete a cycle.
You can split ecological succession into four stages as follows:
- Nudation: the formation of an area devoid of life, for example, due to extreme events like volcanism.
- Invasion: the establishment or arrival of the first species.
- Competition and reaction: increased species numbers and food availability leading to competition and habitat change.
- Stabilization or climax: a relative state of equilibrium maintained by the terminal community.
Human activity can cause the ecological succession process within ecosystems to happen faster than nature intended. Examples include habitat fragmentation and introduced species. Extreme disturbances, which include natural or anthropogenic phenomena like sudden radiation bursts or emissions, can irreversibly alter ecosystems.
Disturbances can be an important part of ecosystems when natural, exactly because they can trigger or stimulate succession. A disturbance's size, frequency, intensity and timing can all affect the rate and direction of successional change (e.g., whether a community recovers its original composition).
Abiotic drivers of succession, such as global warming, produce what is known as an allogenic succession.
Biotic drivers of succession, such as competition for shelter, are classified under the term autogenic succession.
Species succession
- Environments don't necessarily follow a linear pattern of succession, nor do they have to go through or complete all successional stages. Below we can distinguish three categories (pioneers, late-succession, ruderal) used for plant, bacteria and fungi species that succeed each other in an environment. Animal species are also affected by these cycles.
In a new environment, the first organisms to colonize barren or nutrient-poor mediums like barren sand or clear water are typically called pioneer species. When overall biodiversity is low, the pioneers, also known as early-successionals, don't have to compete for resources.
Climax or late-succession species follow up the pioneers and, being better competitors than colonizers, dominate a climax community. In a climax community, nutrient up-cycling and energy consumption may have reached a relative peak and will remain stable for large periods of time (on Earth, hundreds of years) until perturbations start to occur.
Ruderal species are those that colonize heavily disturbed habitats, such as contaminated sites. Ruderal species may be placed in the same category as the pioneers, or may be considered a subdivision of pioneer species, as their colonization strategies are similar. Both are succeeded by climax species.
In all these cases, animal species may be moving in and out of these systems due to their increased mobility when compared to plants.
Lichens (e.g. Lecidea inops) are general pioneer species in the primary succession of rocks. They help with the formation of soil through rock weathering and producing acids. ‘Ōhi‘a lehua (Metrosideros polymorpha) is a native Hawaiian pioneer plant that prefers volcanic mediums and is usually the first native flowering plant to grow in such soils1. On the other hand, Cannabis ruderalis is an example of a plant that grows in nutrient-poor soils such as urban rubble, where not much else grows. It is considered a ruderal plant and a weed due to its invasive potential, more than a classical pioneer species. However, many pioneers can become invasive in altered ecosystems.
Environmental Stability Factors
Biota are the great regulators of Earth's environmental stability because they occur in every habitat on the planet, from the coldest polar regions to the hottest deserts. Populations need to respond to changes and strive to achieve environmental stability thresholds, in order to pass on their genes.
Biotic factors that contribute to environmental stability include:
Biogeochemical regulation: biota mediate the most important cycles on earth, such as the carbon, oxygen, nitrogen, water and phosphorus cycles. These cycles affect atmospheric, water and soil quality, among others.
Nutrient cycling and dispersal: salt-eating organisms (e.g. elks, reindeer, humans) will seek and incorporate salt minerals into their diets. Excretion then spreads the obtained sodium and chloride in a variety of habitats.
Pollutant levels control: microbial bioremediation.
Interaction Between Environment and Biota (examples)
Interactions between the environment and its biotic component can be both direct and indirect. A direct interaction can be represented by an organism directly using sunlight or consuming another organism. An indirect interaction can be that of an organism helping the growth of another by predating on its consumer (see the example below).
Deer feed on willow and aspen saplings and inhibit their growth in certain areas. Wolf predation of deer indirectly aids the willow and aspen growth success rate. This in turn influences the soil quality where those saplings grow.
Below are a few examples of interactions.
Respiration: the exchange of gases between organisms and their environment.
Disease: organisms interacting with the abiotic factors in their environment influence disease processes.
- Decomposition: both biotic and abiotic elements help decompose carcasses which then become hummus, e.g. beetles and water.
- Carbon sequestration: When organisms such as plankton die, they fall to the bottom of the ocean, sequestering carbon away from the atmosphere.
Trophic interactions: foraging and hunting - herbivores, omnivores and carnivores are interlocked in trophic interactions and provide nutrients from these interactions such as urine, faeces, honey, or carcasses.
Rain and moisture: Perspiration - plants transpire most of the water they absorb, aid cloud formation, and even influence wind patterns3. Water and moisture also influence organisms' rate of decomposition and the ability of an environment to sequester carbon4.
Ambient temperature control: Shading - trees in a 2010 study5 significantly reduced soil (over 8 degrees C) and air temperature (over 2 degrees C) compared to unshaded areas during hot seasons.
Earth's biota plays an important role in the regulation of biogeochemical cycles and ecosystem services provision. Without them, our freshwater resources would be less clean, gaseous oxygen non-existent, and we'd have to eat molten rocks! Joking, we are part of the biota too, so we basically wouldn't be here either. I hope you enjoyed the article, and don't forget to check the following ones!
Biota and Environment Stability - Key takeaways
- Biota refers to all organisms (belonging to the Bacteria, Archaea, and Eukarya domains) in an ecosystem. They are essential for maintaining environmental stability.
- Biodiversity health is necessary for keeping ecosystems in balance and providing services that humans rely on.
- Without biota, humans wouldn't have access to important resources like food, clean water, and air filtration.
- Ecological stability is determined by its regenerative and successional qualities, as well as complexity. Succession can be primary and secondary, as well as allogenic or autogenic.
- A variety of interactions occurs between the biota and their environment, including breathing, nutrient dispersal, ambient temperature control, perspiration, etc.
References
- Hawai‘i Forest Institute & Hawai‘i Forest Industry Association, ‘Ōhi‘a lehua, 2016. Accessed 28.05.22
- L. Callum et al., Requirements for natural sunlight to prevent vitamin D deficiency in iguanian lizards, 2001. Accessed 28.05.22
- J. S. Wright et al., Rainforest-initiated wet season onset over the southern Amazon, 2017. Accessed 28.05.22
- J. Zhai et al., Decomposition responses of plant litter to interactive effects of flooding and salinity in Yellow River Delta wetland, 2021. Accessed 28.05.22
- B. Lin et al., Cooling Effect of Shade Trees with Different Characteristics, 2010. Accessed 28.05.22
- S.K. Ernest, Homeostasis, 2008. Accessed 28.05.22
Explanations 
Exams 
Magazine 
