The ecological balance is defined as a state, observable in ecological communities in ecosystems, in which the composition and abundance of species remains relatively stable for a long time.
The idea of a natural balance is part of many philosophical systems and religions. There are those who support the hypothesis of Gaia, according to which the biosphere would act as a system that coordinately maintains, as a supra-organism, the global ecological balance.
The notion of ecological balance supports many environmentalist attitudes in the general public. Ecologists prefer to think in terms of biodiversity conservation, sustainable development, and environmental quality.
Stable ecosystems, in which there is or seems to be a clear ecological balance, abound in nature. For this reason, they appear prominently in the scientific and popular literature. However, there are also unstable ecosystems to which historically less attention has been paid.
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Ecological equilibrium is the result of the capacity of ecological communities to gradually recover, through a process of ecological succession, their original stability, or ecological climax, which has been lost due to a disturbance, be it environmental, biotic or human. that alters the composition and abundance of the species.
The term “ecological succession” refers to the process of directional change in a community after it has suffered a major disturbance. This change takes place in stages and is expressed in the composition and abundance of species, which tend to increase their diversity. Ecological succession has been extensively studied in plant communities.
As a community goes through the stages of ecological succession, it is considered to be out of balance. Upon reaching the final stage of the succession, or ecological climax, the composition of the community is stable, which is why it is considered to be in a state of relative equilibrium.
Ecological equilibrium is a dynamic steady state (homeostasis). Feedback between populations continually compensates, cushioning its effect, minor changes in the composition and population abundances of the community caused by abiotic and biotic factors. As a result, the community returns to its initial appearance..
Ecological equilibrium is the product of the dynamic interaction of two types of factors. First, external disturbances, represented by events, usually of short duration, that cause changes in the composition and abundance of species..
Second, the neutralization of these changes by ecological interactions between the populations that make up the community.
External disturbances can be biotic factors that act episodically. For example, the emergence of migratory species, such as locust infestations in Africa, or pathogens that cause epidemics.
Disturbances can also be sudden abiotic factors, such as hurricanes, floods, or fires..
The ecological interactions that determine the existence of ecological equilibrium include direct interactions (carnivore / prey, herbivore / plant, pollinator / flowers, frugivore / fruits, parasite / host) and indirect interactions (example: carnivore / plant) between the populations that make up each community.
As a result of feedback effects inherent to these interactions, the change in the size of a population is corrected, returning to its equilibrium level, in which the oscillations in the number of individuals are minimal..
Feedback effects are very complex, and therefore particularly vulnerable to disruption by human action, in highly diverse ecosystems, such as tropical rainforests and coral reefs..
During ecological equilibrium, communities achieve relative stability, or steady state, in species composition and abundance. This stability is defined in terms of four main properties, namely: constancy, resistance, resilience and persistence. The latter is also known as inertia.
Constancy is the ability to remain unchanged. Resistance is the ability to remain unchanged as a result of external disturbances or influences. Resilience is the ability to return to the original steady state after a disturbance. Persistence is the ability of populations to conserve themselves over time.
Constancy can be measured by standard deviation, or annual variability. Resistance through sensitivity, or buffering capacity. Resilience through return time, or the magnitude of the deviation that allows that return. Persistence through the mean time to extinction of a population, or other irreversible changes.
For example, an ecosystem that oscillates cyclically around a state, such as that described by the Lotka-Volterra equations to describe the interaction between predators and prey, can be classified as resilient and persistent.
However, it cannot be considered as constant and resistant. In a case like this, two conditions are satisfied that allow it to be considered stable.
The assumption of competition between species plays a major role in the concept of ecological balance. This assumption assumes that in communities there is a balance between productivity and respiration, inward and outward energy flow, birth and mortality rates, and direct and indirect interactions between species..
The assumption of competition between species also assumes that, even in communities that are not in the ecological climax state, there is probably some degree of ecological balance, and that on oceanic islands there is a balance between immigration and extinction of ecologically equivalent species..
The survival of the species that make up a population depends on the persistence of those same species at the metapopulation level. The exchange of individuals and recolonization between populations of the same species that inhabit nearby communities maintains genetic diversity and makes it possible to remedy local extinctions.
At the metapopulation level, survival implies: a) populations distributed in discrete microhabitas; b) microhabitats close enough to allow their recolonization from other microhabitats; c) greater probability of extinction at the population level than at the metapopulation level; and d) low probability of simultaneous extinction in all microhabitats.
Consider the case of wolves that, after many decades of being exterminated by ranchers, were reintroduced into Yellowstone National Park in the United States to restore the ecological balance lost due to overpopulation of large herbivorous mammals..
The initial growth of the wolf population dramatically decreased herbivorous mammal populations, which in turn put a limit on the population size of the former (fewer herbivores means that many wolves do not have enough food and starve, or they do not produce puppies).
The lower and more stable levels of herbivore populations thanks to the presence of also stable populations of wolves allowed the reappearance of the forests. This in turn allowed the recolonization of Yellowstone by a large number of species of forest birds and mammals. In this way, the park recovered its original splendor and biodiversity..
Other examples of communities in apparent ecological balance are found within national parks and marine reserves in which the laws that protect them are enforced, or in remote areas with low human densities, particularly when the inhabitants are indigenous who make little use of technologies. modern.
The current rate of environmental destruction far exceeds the ability of ecosystems to regain their natural ecological balance.
The situation is unsustainable and cannot continue for long without seriously damaging humanity. The loss of biodiversity makes it increasingly difficult to find species to rebuild natural communities and ecosystems.
For the first time in its history, humanity is facing three dangerous disturbances on a planetary scale: 1) climate change, one of whose most obvious facets is global warming; 2) pollution and acidification of the oceans; and 3) an enormous loss, at unprecedented speed, of global biodiversity.
These large-scale disturbances will strongly affect the younger members of current generations and future generations. There will be large numbers of climate refugees. Fishery resources will decline. You will see a world devoid of many of the wild plant and animal species that we are used to..
On this subject, it is recommended to consult the work of Ripple et al. (2017). These authors point out that to achieve the transition towards a global ecological balance it would be necessary:
1) Create nature reserves that protect a significant fraction of the terrestrial and aquatic habitats of the planet.
2) Stop the conversion of forests and other natural habitats in areas under intensive exploitation.
3) Restoring native plant communities on a large scale, especially forests.
4) Repopulate large regions with native species, particularly top predators.
5) Implement policies to remedy defaunation, exploitation and trade in threatened species, and the global crisis caused by the consumption of wild animals.
6) Reduce food waste.
7) Promote the consumption of plant foods.
8) Reduce human population growth through education and voluntary family planning.
9) Educate children in the appreciation and respect of nature.
10) Channel monetary investments towards positive environmental change.
11) Design and promote green technologies, reducing subsidies for the consumption of fossil fuels.
12) Reduce economic inequality and ensure that prices, taxes and incentives take into account the environmental cost.
13) Unite nations to support these vital goals.
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