IPAT unpacked
IPAT was developed by Paul and Anne Ehrlich 50 years ago [7, 8]. It is a system for understanding impact based on the interaction between the three factors of population P, affluence A, and technology T. It uses the equation:
Impact = Population x Affluence per capita (measured by GDP/person) x Technology per unit of Impact (measured by various impacts like carbon intensity).
I worked with the Ehrlich’s at Stanford in the early 1970’s and was heavily influenced by this model, teaching it for many years and writing my first environmental paper showing how the model could be applied at a national level [22, 23]. IPAT has a strong appeal to common sense that if we are impacting on the global environment then we simply have to reduce population, reduce the economy which causes our over-consumption of the earth, and reduce the technology that is responsible for our impact on the earth.
Unfortunately, IPAT does not leave much hope - for getting a job or reason for having children (both pretty basically dependent on continuing civilization). It can lead to eco-anxiety and even notions of ‘civicide’ [14]. The term ‘eco-anxiety’ was the Oxford word of the year in 2019 but I was aware of its tentacles in the early 1970’s and 1980’s as we began to see the enormity of the issues from global climate change, air pollution, water pollution, loss of biodiversity, and resource constraints like oil. But I could never quite enter into the despair of ‘civicide’ as I kept getting involved in political actions for environmental change and winning! Hope is generated from success in achieving beneficial change as well as from beginning to see a different vision of the future that was emerging, bit by bit [21, 30].
This eventually led me to try and see where we could find a more hopeful model and much of my academic work since has been attempting to show it is possible to find hope in a time of civicide. This work is in finding new technologies, new economic models, new urban planning processes, new politics and new understandings of how we live together on this earth (eg [20, 21, 24, 27, 30, 31, 33,34,35]). But, before now, I have not related this back to the IPAT model with its powerful arithmetic. So, let me try and do so now.
Deconstructing the arithmetic in IPAT
It is possible to challenge the arithmetic of IPAT by examining the nature of growth. In this system of thinking:
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Population is seen simply as a multiplying factor on the other two components which are both seen to be inevitably negative.
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Economic activity uses GDP per person to represent how the technology used to create a product is seen to represent consumption of the product thus any economic activity is seen as negative, no matter what it is for; and
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Technological impact is then at the base of the system creating the impact but this is also seen as inevitably negative, as it mostly was at that time when the Ehrlich’s first promulgated IPAT.
Hence the growth in the economy and the increasing number of people inevitably cause all the problems simply by multiplying the impact of growing population based on inevitably negative impacts from all three factors.
It is possible to see how this can be changed as economic activity and technological change are introduced into the system without having inevitable impact. The paper will therefore set out three stages in development – exploitive, sustainable and regenerative – that change the IPAT arithmetic.
Stage 1 exploitive development
Stage 1 is the exploitive development era, the historic context for the development of IPAT when all three of the components of IPAT appeared to be out of control and were growing exponentially. Figure 1 grows exponentially out of control as all three factors are growing.
However, we have had over 50 years of global action on environmental regulation, environmental technology, environmental assessment and all kinds of environmental governance at global, national and local level driven by strong demand from communities and by some industries. I believe we don’t do justice to this work applying the IPAT model now as the model assumes these factors have not changed and exponential growth in impact will simply continue. Environmental change just disappears under the broad categories of population, affluence and technology, inevitably riding over any reforms. However, these reforms can act on impact without necessarily reducing population or economic growth even within the arithmetic logic of IPAT. But it takes some changes to make the system begin to turn around.
Stage 2, sustainable development
If the technology used for creating products and services reduces its impact then the whole system can be improved if it is a big enough change; this is clear in the arithmetic. IPAT reduces impact though it does not mean the overall impact is still not made worse by population and economic growth increases. But it is less impact per unit of population or per unit of economic output and that is a start. I am calling this Stage 2 after getting out of the horrible Stage 1 of exponential growth caused by completely exploitive practices at all levels.
At Stage 2 there is still largely a source of despair as overall impact is still going up even if it has slowed a little. So, people cannot always see how having children could be a hopeful exercise and even economic growth is still largely seen as part of the problem, not part of the solution. This is one of the reasons why there has been a growing division in the world between those who are environmentally-oriented and those who are economically-oriented. It is why the World Commission on Environment and Development was set up and produced the idea of sustainability to try and bring these divisions together, at least in theory [48]. In my reading this has not been related to the arithmetic of IPAT. So, I will show here how it is possible to see how the sustainable development approach works on IPAT if it can be substantial enough:
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Some people will choose to reduce their impact through all their life choices (so P can be lessened);
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Some consumption-oriented economic activity can be changed to reduce environmental impact (so A can be lessened); and
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Some technologies will change to reduce their impact for each product produced (so T is also lessened).
The three reductions together combine to make a reduced impact as was clearly the desired outcome from the sustainable development agenda and how this has now led to the Sustainable Development Goals. The three elements of the IPAT equation will mean that there is a system of all three combining to reduce the impact, that would have been, if there had been no change. The idea is that it is minimized to enable more social and economic development. That is the fundamental idea behind sustainability. Its overall outcome is designed to flatten the curve of impact.
Figure 2 shows how this Stage 2 of Sustainable Development means that the exponentially growing impact begins to slow and eventually reaches a plateau.
This Stage 2 of the transition away from global environmental impact is the basis of what is now called Decoupling as shown in Fig. 3 where the G20 nations are summarised in their reductions in impact per unit of population and per unit of economic activity.
Economic growth continues upwards during decoupling but greenhouse gases and other pollution or impacts start reducing and declining. The G20 nations are all decoupling absolutely i.e. they are declining in emissions per capita as per capita GDP goes up ClimateTransparency. Brown to Green Report, Climate Transparency, Berlin, Germany; 2017. We have shown this to be the case in many parts of the world on greenhouse emissions with European nations starting earlier but strong signs now evident in Australia, the US, and China and developing nations like India still increasing emissions and fossil fuel consumption but starting to relatively decouple GHG from economic growth (see [31]; and [28, 36, 46]). So, the overall picture of GDP or GNI vs GHG is now much more positive than it was when IPAT was created (see Fig. 4).
The significance for me here is that there is hope because the changes can happen within:
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the Population factor (people make choices to reduce impact and hence not all population is the problem),
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the Affluence factor (the economic system can be adapted to have lower impact in the process of creating GDP) [18], and
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the Technology factor (the technological system can indeed be a driver of reduced impact).
However, this is still seen by many as being a problem. Despite the rapid change total global impact is still growing despite being much reduced in its growth due to reductions in per capita and per unit of economic activity. Thus, from an IPAT perspective it is not enough as in a finite world it will eventually hit biophysical limits [21, 41]. So, we are still left with the inevitable march towards civicide, though perhaps postponed somewhat.
The reduction of impact can begin small and then grow to be a significant reduction but reduction in per capita is not enough if population is increasing. With the apocalyptic start to 2020 we need to see more or IPAT will keep showing we can never win unless population and economic growth collapse. However, once Stage 2 begins to rollover the top of the curve and start going down, it is a new world that starts unfolding. Stage 2 of the transition begins to absolutely reduce environmental impact in total and offers some hope as it begins to exponentially decrease – just as the problems were exponentially increasing in Stage 1. This is a very significant step and one deserving of hope.
But the big change in understanding IPAT comes when Stage 3 is reached and the system begins to regenerate.
Stage 3 regenerative development
If the technology for producing products and services is so changed that it can be regenerative, then we have a totally different perspective on IPAT. Regenerative economic activity and regenerative technology is not just reducing impact it is beginning to regenerate the damaged environment. With regenerative development a whole new system emerges. Using IPAT it is possible to see new opportunities for creating hope in a more sustainable earth.
The IPAT equation in the regenerative Stage 3 is about:
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Technology that is regenerative, i.e. it is able to not just reduce impact but to regenerate the damage created before. For example, the infrastructure and services of a city could:
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Make more renewable energy than the city consumes as well as sucking CO2 from the atmosphere using carbon absorbing cement, carbon-negative plastics, biogenic building materials, and carbon-negative landscaping [9].
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Recharge depleted aquifers and rivers.
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Restore soils and N/P balance in the bioregion as it uses circular economy principles with its waste,
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Regenerate biodiversity through biophilic habitats on buildings [16, 25, 26, 42]; and
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All the while growing the community and the economy.
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Affluence or the consumption of products measured by GDP is now driven by fuels, materials, recyclability, and processes that begin to clean up damaged ecosystems, including the atmosphere with its CO2 no longer growing but declining back to a manageable level.
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Population now becomes a driving force for regeneration as arithmetically every person added is now using this new economic system and the technological drivers of it, so they will improve the rate of regeneration.
Thus, with regenerative development both population and economic growth can be welcomed as they are driving lots of good. Not just doing less and less bad.
This is shown in Fig. 5 where development is regenerating and reclaiming the environment. One word increasingly used in IPCC is transformative [17]. The hope issue then reduces to whether this is likely to happen and how soon. In my world, this is easiest seen through the rapid change in the agenda for cities where regenerative development is replacing sustainable development [16, 43].