Ecological Collapse
Pedro L. Lomas and Mateo Aguado.
In Ecology it is customary to speak of ecological succession when referring to the development process unfolding in a given ecosystem from its early stages to maturity, in which the system’s biomass and stability tend to reach their peak. Thus, ecological succession is a natural process in which an ecosystem undergoes gradual and directional changes over time as a result of its self-organisation (Margalef, 1974). From this viewpoint, it is assumed that an ecosystem reaches maturity (sometimes the botanical term climax is used), when its food networks (circulation of matter and energy) reach their maximum development in time and space in relation to the surrounding environment.
In practice, however, it is hard to find cases of permanent stability in nature and, when identified, these are of relatively short duration. Overall, ecosystems’ natural variability produces disturbances that introduce changes, of greater or lesser intensity, causing interference at different stages in this self-organisation process and keeping ecosystems within a dynamic variation range known as the stability domain.
In the past, taking into account human actions, these disturbances were commonly considered as external to the ecosystem, without whose action, following a linear or determinist line of thought, the latter would tend to systematically reach the mentioned foreseeable state of equilibrium or maturity, viewed as its optimal condition. The time required by the ecosystem to reach a state of maturity or stability prior to an external disturbance constituted what some authors call resistance or engineering resilience (Holling, 1986, 1996; Gunderson, 2000; Lake, 2013).
However, today we know that natural disturbances constitute an essential characteristic inherent to ecosystems’ evolutional development, by contributing to their renewal through provoking processes of disorganisation or temporary collapse, giving way to new processes of self-organisation (Odum, 1969; Holling, 1973; Odum et al. 1995; Gunderson & Holling, 2022). This is what happens, for instance, with flooding in fluvial ecosystems or wildfire in forest ecosystems, which contribute to the elimination of the system’s weakest and oldest organisms, thus opening up space for new generations of organisms to prosper, given the appropriate conditions. In this sense, generally speaking, ecosystems’ structural self-regulation mechanisms allow them to absorb a certain degree of variability caused by disturbances (natural or anthropic) without shifting their stability domain. This is known as ecological resilience (Holling, 1973; Gunderson & Holling, 2002).
Moreover, it has also been shown that changes in nature often follow non-linear dynamics in which the effect is not always proportional to the cause. This more or less unpredictable behaviour in ecosystems, that is a general characteristic of all complex systems, tells us that their dynamic is not really as deterministic as formerly believed, but rather, that it operates on a multiple path logic (Levin, 1998, 2005). This is why, when a disturbance is of a magnitude that surpasses the ecological resilience of an ecosystem, the object of the new self-organisation may differ from the point of departure, causing an abrupt shift in the nature of the ecosystem on pushing it out of its original stability domain. Overstepping certain ecological thresholds can thus cause ecosystems to exceed -suddenly, and sometimes to a point of no return- their tipping point, from which moment the ecosystem will move toward a new stability domain (Scheffer et al. 2001; Scheffer & Carpenter, 2003; Biggs et al., 2012).
This process is commonly referred to as ecological collapse, and occurs when the original ecosystem becomes disorganised in such a manner that the new self-organisation process, instead of renewing and recovering its former stability domain, leads to a different domain with a different range of characteristic biogeophysical variables.
Ecological collapse is a process that can become irreversible owing to the various traps the ecosystem may fall into. Thus, the new state may remain over time because its recovery would demand unmeetable requirements in terms of matter and energy (a consequence of the second thermodynamic law), or thanks to the high level of resilience in the ecological system’s new configuration, in part also the result of the second law of thermodynamics (Scheffer et al., 2001; Dakos et al., 2019). A local example would be a forest that has been felled, and in which irreversible soil loss and erosion processes have occurred, causing it to become a degraded area and, in time, an arid land. On a global scale, we can also envisage, for example, the composition of the atmosphere as a part of the biogeophysical variables that condition the current state of the biosphere, and the increase in greenhouse gases as a disturbance liable to make the planet Earth uninhabitable for certain species, including human beings.
The fact that human societies are settled in ecosystems and depend upon their structure, operation and dynamics (ecodependence) makes it feasible that, in some cases, ecological collapse may entail a considerable risk of leading to social collapse at a certain scale.
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