Ecological threshold is the point at which a relatively small change or

disturbance Disturbance and its variants may refer to: Math and science * Disturbance (ecology), a temporary change in average environmental conditions that causes a pronounced change in an ecosystem * Disturbance (geology), linear zone of faults and folds ...

in external conditions causes a rapid change in an

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syst ...

. When an ecological threshold has been passed, the ecosystem may no longer be able to return to its state by means of its inherent

resilience Resilience, resilient, resiliency, or ''variation'', may refer to: Science Ecology * Ecological resilience, the capacity of an ecosystem to recover from perturbations ** Climate resilience, the ability of systems to recover from climate change * ...

. Crossing an ecological threshold often leads to rapid change of

ecosystem health Ecosystem health is a metaphor used to describe the condition of an ecosystem.Rapport, David (1998). "Defining ecosystem health." Pages 18-33 in Rapport, D.J. (ed.) (1998). ''Ecosystem Health.'' Blackwell Scientific. Ecosystem condition can vary ...

. Ecological threshold represent a

non-linearity In mathematics and science, a nonlinear system is a system in which the change of the output is not proportional to the change of the input. Nonlinear problems are of interest to engineers, biologists, physicists, mathematicians, and many ot ...

of the responses in ecological or biological systems to pressures caused by human activities or natural processes. Critical load, regime shift,

critical transition Critical transitions are abrupt shifts in the state of ecosystems, the climate, financial systems or other complex dynamical systems that may occur when changing conditions pass a critical or bifurcation point. As such, they are a particular type ...

and tipping point are examples of other closely related terms.

Characteristics

Thresholds can be characterized as points or as zones. Zone-type thresholds imply a gradual shift or transition from one state to another rather than an abrupt change at a specific point. Ecological thresholds have caught attention because many cases of catastrophic worsening of conditions have proved to be difficult or nearly impossible to remedy (also known as points of no return).

Ecological extinction Ecological extinction is "the reduction of a species to such low abundance that, although it is still present in the community, it no longer interacts significantly with other species". Ecological extinction stands out because it is the interacti ...

is an example of a definitive point of no return. Ecological thresholds are often characterized by

hysteresis Hysteresis is the dependence of the state of a system on its history. For example, a magnet may have more than one possible magnetic moment in a given magnetic field, depending on how the field changed in the past. Plots of a single component of ...

, which means the dependence of the state of a system on the history of its state. Even when the change is not irreversible, the return path from altered to original state can be drastically different from the development leading to the altered state. Another related concept is

panarchy Panarchy may refer to: * Panarchy (Dartmouth), student society at Dartmouth College * Panarchy (ecology) A social-ecological system consists of 'a bio-geo-physical' unit and its associated social actors and institutions. Social-ecological system ...

. Panarchy views coupled human-natural systems as a cross-scale set of adaptive cycles that reflect the dynamic nature of human and natural structures across time and space. Sudden shifts in ecosystem state can induce changes in human understanding of the way the systems need to be managed. These changes, in turn, may alter the institutions that carry out that management and as a result, some new changes occur in ecosystems.

Detection

There are many different types of thresholds and detecting the occurrence of a threshold is not always straightforward. One approach is to process

time series In mathematics, a time series is a series of data points indexed (or listed or graphed) in time order. Most commonly, a time series is a sequence taken at successive equally spaced points in time. Thus it is a sequence of discrete-time data. Ex ...

which are thought to display a shift in order to identify a possible jump. Methods have been developed to enhance and localize the jumps.

Examples

Some examples of ecological thresholds, such as clear lakes turning into turbid ones, are well documented but many more probably exist. The thresholds database by Resilience Alliance and

Santa Fe Institute The Santa Fe Institute (SFI) is an independent, nonprofit theoretical research institute located in Santa Fe, New Mexico, United States and dedicated to the multidisciplinary study of the fundamental principles of complex adaptive systems, inclu ...

includes over one hundred examples.

References

External links

Resilience Alliance
A multidisciplinary research group that explores the dynamics of complex adaptive systems
Thresholds of environmental sustainability
A research project focusing on ecological thresholds {{DEFAULTSORT:Ecological Threshold Ecological economics Ecology terminology

Characteristics

Detection

Examples

See also

References

External links