I = PAT
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I = (PAT) is the mathematical notation of a formula put forward to describe the
- I = P × A × T
The expression equates
The validity of expressing environmental impact as a simple product of independent factors, and the factors that should be included and their comparative importance, have been the subject of debate among
History
The equation was developed in 1970 during the course of a debate between
The equation can aid in understanding some of the factors affecting human impacts on the environment,[5] but it has also been cited as a basis for many of the dire environmental predictions of the 1970s by Paul Ehrlich, George Wald, Denis Hayes, Lester Brown, René Dubos, and Sidney Ripley that did not come to pass.[6] Neal Koblitz classified equations of this type as "mathematical propaganda" and criticized Ehrlich's use of them in the media (e.g. on The Tonight Show) to sway the general public.[7]
The dependent variable: Impact
The variable "I" in the "I=PAT" equation represents environmental impact. The environment may be viewed as a self-regenerating system that can endure a certain level of impact. The maximum endurable impact is called the carrying capacity. As long as "I" is less than the carrying capacity the associated population, affluence, and technology that make up "I" can be perpetually endured. If "I" exceeds the carrying capacity, then the system is said to be in overshoot, which may only be a temporary state. Overshoot may degrade the ability of the environment to endure impact, therefore reducing the carrying capacity.
Impact may be measured using
Impact is modeled as the product of three terms, giving gha as a result. Population is expressed in human numbers; therefore affluence is measured in units of gha per capita. Technology is a unitless efficiency factor.
The three factors
Population
In the I=PAT equation, the variable P represents the population of an area, such as the world. Since the rise of industrial societies, human population has been increasing exponentially. This has caused
The United Nations project that world population will increase from 7.7 billion today (2019) to 9.8 billion in 2050 and about 11.2 billion in 2100.[8] These projections take into consideration that population growth has slowed in recent years as women are having fewer children. This phenomenon is the result of demographic transition all over the world. Although the UN projects that human population may stabilize at around 11.2 billion in 2100, the I=PAT equation will continue to be relevant for the increasing human impact on the environment in the short to mid-term future.
Environmental impacts of population
Increased population increases humans' environmental impact in many ways, which include but are not limited to:
- Increased land use - Results in habitat loss for other species
- Increased resource use- Results in changes in land cover
- Increased pollution - Can cause sickness and damages ecosystems
- Increased climate change
- Increased biodiversity loss
Affluence
The variable A in the I=PAT equation stands for
Environmental impacts of affluence
Increased consumption significantly increases human environmental impact. This is because each product consumed has wide-ranging effects on the environment. For example, the construction of a car has the following environmental impacts:
- 605,664 gallons of water for parts and tires;[9]
- 682 lbs. of pollution at a mine for the lead battery;[9]
- 2178 lbs. of discharge into water supply for the 22 lbs. of copper contained in the car.[9]
The more cars per capita, the greater the impact. Ecological impacts of each product are far-reaching; increases in consumption quickly result in large impacts on the environment through direct and indirect sources.
Technology
The T variable in the I=PAT equation represents how resource intensive the production of affluence is; how much environmental impact is involved in creating, transporting and disposing of the goods, services and amenities used. Improvements in efficiency can reduce resource intensiveness, reducing the T multiplier. Since technology can affect environmental impact in many different ways, the unit for T is often tailored for the situation to which I=PAT is being applied. For example, for a situation where the human impact on climate change is being measured, an appropriate unit for T might be greenhouse gas emissions per unit of GDP.
Environmental impacts of technology
Increases in efficiency from technologies can reduce specific environmental impacts, but due to increasing prosperity these technologies yield for the people and businesses that adopt them, technologies actually end up generating greater overall growth into the resources that sustain us.
Criticism
Criticisms of the I=PAT formula:
- Too simplistic for complex problem
- Interdependencies between variables
- General sweeping assumptions of variables' effect toward environmental impact
- Cultural differences cause wide variation in impact
- Technology cannot properly be expressed in a unit. Varying the unit will prove to be inaccurate, as the result of the calculation depends on one's view of the situation.
Interdependencies
The I=PAT equation has been criticized for being too simplistic by assuming that P, A, and T are independent of each other. In reality, at least seven interdependencies between P, A, and T could exist, indicating that it is more correct to rewrite the equation as I = f(P,A,T).
Neglect of beneficial human impacts
There have also been comments that this model depicts people as being purely detrimental to the environment, ignoring any
Neglect of political and social contexts
Another major criticism of the I=PAT model is that it ignores the political context and decision-making structures of countries and groups. This means the equation does not account for varying degrees of power, influence, and responsibility of individuals over environmental impact.
Policy implications
As a result of the interdependencies between P, A, and T and potential rebound effects, policies aimed at decreasing environmental impacts through reductions in P, A, and T may not only be very difficult to implement (e.g.,
See also
- Affluence
- Carbon footprint
- Eco-economic decoupling
- Ecological footprint
- Ecological indicator
- Embodied energy
- Kaya identity
- Life cycle assessment
- Population growth
- Sustainability measurement
- Sustainability metrics and indices
- Technology
- Water footprint
References
- ^ O'Neill, B.C.; MacKellar, F.L.; Lutz, W. (2004). "Population, greenhouse gas emissions, and climate change". In Lutz, W.; Sanderson, W.C.; Scherbov, S. (eds.). The End of World Population Growth in the 21st Century: New Challenges for Human Capital Formation & Sustainable Development. London: Earthscan Press. pp. 283–314.
- PMID 5545198.
- ^ Chertow, Marian (2001). "The IPAT Equation and Its Variants". Changing Views of Technology and Environmental Impact.
- ^ .
- S2CID 153623657.
- ^ R Bailey (2000) Earth day then and now, Reason 32(1), 18-28
- ^ N Koblitz (1981) "Mathematics as Propaganda", in Mathematics Tomorrow, ed. Lynn Steen, pp 111-120.
- ^ "Population Prospects 2017" (PDF).
- ^ .
- ^ .
- ISBN 0865717044, 464 pp.
- S2CID 153936260.≥
- ^ ISBN 978-1-4051-8931-6.
- OCLC 13516436.
- OCLC 40762824.
- S2CID 7165162.
- S2CID 13982607.
- S2CID 250227342.
- . Retrieved 21 June 2023.
External links
- Media related to I = PAT at Wikimedia Commons