An ecosystem is a community of living organisms that interact with one another, as well as with other components of the same community (the natural environment), in order to sustain life.
The interplay of all these components – organisms, environment, and the way individuals interact with each other – is complex and often difficult to unravel. However, in order to better understand the role of different elements in the structure and function of an ecosystem, it is useful to isolate and examine each one of these factors independently.
Organisms are the parts of an ecosystem that are characterized by their capacity to independently live and interact with one another. However, this does not mean that all organisms are equal; some are more significant than others depending on the context. Macroalgae, for example, are a type of plants that can grow to a considerable size and thus can have a significant impact on the environment as a whole. Similarly, large animals such as certain crabs and fish can have a big impact on the ecosystem as a whole by consuming some of the smaller organisms that make up the food web.
A food web is a simplified representation of an ecosystem that shows the interactions that occur between different types of living organisms. These interactions can be either positive (mutualistic) or negative (competitive or parasitic).
Organisms can be either consumers or producers of energy. Consumers, also known as herbivores, directly eat other organisms (mainly plants) and thus require energy in order to sustain themselves. Producers, or carnivores, on the other hand, eat organisms that are smaller than themselves, hence requiring and providing energy to the community as a whole. As the name would suggest, producers tend to play a more important role in an ecosystem as they provide raw material (food) for other organisms.
The environment is everything around the organism that is not chemically bound to it. The term is often used in reference to the abiotic (non-living) factors of an ecosystem such as water, air, and light, as well as the living organisms themselves. The environment also encompasses all the non-living (inorganic) materials such as soil, sand, and rock which the organisms inhabiting the ecosystem require in order to grow.
In biotic environments (i.e. where living organisms are present), the abiotic factors are generally more significant than the living organisms themselves. In such cases, the environment can be considered as a host for the community of living organisms. Similarly, extreme changes in the environment (such as those brought about by climate change) can have significant impacts on the entire ecosystem, driving some species to extinction and changing the composition of the community entirely. For example, sea levels may rise significantly due to climate change, threatening the existence of some animals and plants that are completely dependent on the interaction with the ocean. Species that are unable to adapt to the changed circumstances can become threatened or even go extinct.
Individuals (or Boids)
In the scientific literature, the individual organism is often referred to as the ‘boid’ and the social grouping of organisms is referred to as the ‘swarm’. A boid is an organism that displays collective (and thus apparently intelligent) behavior. In other words, it is the unit of evolution in the swarm theory of Edward O. Wilson, a prominent biologist who introduced the concept.
Boids are commonly found in nature and can be observed in groups (swarms) of various sizes and compositions, including fish, birds, and larger land animal aggregations. In some cases, boids even cooperate and work together to achieve shared goals, displaying leadership skills and creating efficient work groups. Boids are usually characterized by their ability to rapidly coordinate their actions through social interactions and by their apparent sensitivity to changes in their environment, displaying what appears to be collective learning behavior. Finally, boids are typically more mobile than sedentary, traveling from place to place in order to find food and mates.
An individual that is part of a swarm may behave differently from an organism that is operating in isolation. For instance, a bee which has been removed from its hive will act in a frenetic manner trying to establish contacts with other bees in order to rejoin its colony. Similarly, a fish out of water will frantically swim towards the surface in search of air, which it needs in order to survive. In such cases, the individual may temporarily lose its connection to the ecosystem as a whole, becoming a “thing” in itself rather than playing a functional role in the community it inhabits.
The interactions between the different factors of an ecosystem are of paramount importance for its overall functioning. Just like different organs in the body interact with each other in order to sustain life, so too different components of the ecosystem interact with one another. Some of these interactions are direct and require no mediation, while others are more subtle and require some form of communication or coordination between the parties involved.
Mutualistic interactions, for example, can occur between different types of plants, which sustain each other through a process of photosynthesis (plant food production). In turn, these plants provide the forest ecosystem as a whole with nutrients (nitrogen) which contribute to the creation of food for other animals. In other words, through the process of photosynthesis, one organism provides food for another which in turn provides food for a third organism, and so on, creating a chain of dependency. In a similar manner, animals such as the ones mentioned earlier which consume smaller organisms provide these smaller organisms with nutrients which they require in order to grow and sustain themselves. In this case, all parties benefit from the interaction and no one is harmed at the end of the day.
More subtle interactions can occur between the components of the ecosystem as a whole. When one type of organism (a herbivore, for example) significantly outnumbers another type (a carnivore), the members of the former will tend to eat the latter. However, since carnivores are essential for maintaining a healthy ecosystem, they will usually survive rather than go extinct. In other words, when one type of organism significantly outnumbers another, the first will usually win the evolutionary arms race and the latter will become “extincted” (i.e., it will no longer exist in the population). Similarly, when there is a lack of predators in the ecosystem, the prey (mostly herbivorous animals) will increase in number until the ratio becomes more balanced. In the long term, this may lead to an unsustainable amount of herbivorous animals and thus to the decline of the entire ecosystem. In this case, the interaction between different types of organisms are not so much about sustaining life as they are about keeping the equilibrium and stability of the ecosystem as a whole.
The function of an ecosystem is best described as the process that occurs as a result of the interplay between its different components. In simpler terms, it can be considered as the role that different elements play in sustaining life.
An ecosystem is usually described as ‘serviceable’ when all of its different parts work together in harmony to fulfill their specific functions. When one or more of these functions are altered due to environmental or anthropogenic factors, this can lead to significant changes in the way the ecosystem functions. In these cases, the ecosystem becomes progressively less and less serviceable until it finally collapses and ends up in a state of disarray or dysfunctionality.
When an ecosystem collapses, it does not mean that all is lost. Just as a human survivor of a catastrophe will try its best to rebuild what has been destroyed, so too will the diverse range of creatures that made up the original ecosystem try to resurrect what has been lost. The process of recovery, however, will not be easy. Just as the survivors of a catastrophe will have to deal with the psychological and spiritual ramifications of what they have been through, so too will the animals of a collapsing ecosystem have to come to terms with what has happened. In the case of humans, this may even lead them to try and prevent further environmental destruction by changing their behavior and becoming more eco-friendly. Similarly, marine life in particular will be driven by a quest for survival and thus will try to migrate back to their usual places of habitation when the waters around them return to normal (as much as possible). Although the process of recovery will be difficult, it is certainly doable and thus the ecosystem as a whole does not have to end up in total ruin. While some elements may take longer than others to get back on their feet, overall the ecosystem will be revived and it will be able to function as it did before. Of course, this is assuming that human activity does not exceed the natural limits that the ecosystem can withstand. When this happens, the entire ecosystem will suffer and potentially become unsustainable. In this case, recovery can become entirely impossible and the “bloomerang” effect will set in, with one component (usually biological) attacking and reducing the numbers of another (usually a predator) thus perpetuating a cycle of destruction.