Revised 2 December 2023

Humanity is in ecological/planetary overshoot. It is critical to understand that climate change is but one of many symptoms of a wider ecological overshoot manifested in biodiversity loss (for example, massive declines in pollinating insects), collapse of ecosystems, pollution, resource depletion, and soil depletion. We have already exceeded Earth’s carrying capacity and our current ecological footprint exceeds our global bio-capacity by at 56% (Wackernagel et al. 2021). We are rapidly eroding our own ecosphere, the life-support system upon which we all depend. We have already crossed several critical thresholds, and are dangerously close to many others (Rockström 2009; Seibert and Rees 2021). 

The dominant ethos of our Western culture over the past 200 years has been economic growth made possible by fossil fuels which are a convenient and energy dense form of energy. Abundant and cheap fossil fuels have enabled exponential growth in world population and economies as measured by GDP. 

The burning of fossil fuels and emissions of greenhouse gases has resulted in human-induced climate change. We must reduce fossil fuel consumption to put a brake on the already disastrous impacts of climate change which, if left unaddressed, is an existential threat to all forms of life on Earth (Lenton et al. 2008; Steffen et al. 2018). 

Renewable energy (non-fossil fuel energy such as wind, solar, hydro, and geothermal) cannot bootstrap the formation of renewable energy infrastructure by itself. Continued use of fossil fuels is required to enable a transition at the very same time we need to immediately reduce consumption of fossil fuels. But the energy returned on energy invested (EROI) to extract fossil fuels from the ground is declining. There are strong indications that conventional oil production has peaked, the maximum rate of extraction has plateaued, and the net energy available from global fossil fuel production has peaked and will now decline (Hall et al. 2014; Chapman 2014; Delannoy et al. 2021; Bihouix 2021; Rech et al. 2021). Declines in EROI can only but accelerate. 

In New Zealand, about 75% of our electricity was generated by ‘renewables’ (hydro, wind, geothermal, solar) in 2017, but only 32% of NZ total energy use was from ‘renewables’. The remaining 68% of total energy use was from fossil fuels (LLNL/US Dept Energy/IEA 2021). If we wanted to 100% electrify our economy, then we would have to triple our electrical generation capacity. 

Renewable energy has a much lower EROI than conventional oil in the Twentieth century when the EROIs of fossil fuels was much higher than it is now (Seibert & Rees 2021; Capellán-Pérez et al. 2019). Battery storage of renewable energy is less energy dense and portable for transport purposes than fossil fuels (Seibert & Rees 2021). 

It is impossible to scale up renewable energy to meet current energy per-capita levels because renewable energy is critically dependent on the use of scarce and rare minerals (Michaux 2021; Bihouix 2021). Reaching “net zero” globally by 2050 – far too late to avoid climate catastrophe - would require six times the amount of mineral resources used today (IEA 2021). We would have to use fossil fuels to mine these materials and build, implement, and replace this enormous renewable energy infrastructure. At the same time, the net energy available from fossil fuels will soon peak and then will begin to decline (Delannoy 2021). We simply cannot quantitatively replace current energy consumption provided mainly by fossil fuels with energy from renewables (Michaux 2021; Krumdieck 2021; Seibert & Rees 2021; Bihouix 2021). 

High EROIs of fossil fuels enabled exponential growth in populations and economies in the Twentieth Century. In the Twenty First Century, we now face a future where there will be less energy per capita. Continued increases in consumption per capita will be impossible. Less energy per capita means less consumption per capita. Priorities as to what constitutes non-essential consumption over and above essential consumption will need to be examined and revised. 

Any attempts to continue business-as-usual economic growth while also avoiding climate change through a transition from fossil fuels to renewables will only but lead towards increasing ecological overshoot and collapse through biodiversity loss, ecosystems breakdown, soil depletion, resource depletion, and all the other symptoms of overshoot. Whether it is powered by fossil fuels or renewable energy, continued economic growth – the expansion of the human enterprise in a finite world - can only lead to ecological and social decline and collapse (Demaria 2018; Herrington 2021; Seibert and Rees 2021). 

We need to rapidly reduce our emissions of greenhouse gases, starting immediately, to mitigate the impact of climate change by reducing our use of fossil fuels. At the same time, we still need to use fossil fuels to enable a transition from fossil fuels to that of renewable energy and infrastructure (Seibert and Rees 2021). The only way out of this conundrum is to radically reduce our current levels of consumption and divert the use of fossil fuels away from extravagant and unnecessary consumption to a limited renewable energy system that can support a lower-energy society. 

Reducing our consumption of fossil fuels means keeping most of our fossil fuel reserves in the ground to avoid exceeding critical climate change threshold (McGlade & Ekins 2014). Further exploration of fossil fuels would be a waste of energy and reduce our budget of fossil fuels which we need to enable a transition. If we squander our limited budget of fossil fuels on foolhardy explorations for more fossil fuels and frivolous consumption, then we will lose our last chance to make a global transition to renewable energy and infrastructure. 

It is logically impossible for perpetual economic and population growth to occur on a finite planet. Sustainable economic growth is an oxymoron and empirical evidence on resource use and carbon emissions does not support green growth theory (Hickel & Kallis 2020). Either we have a planned, orderly contraction (de-growth) of our economy or else a far more chaotic contraction will be forced upon us by nature, likely within a decade from now (Herrington 2020). 

Climate change is but only one of many symptoms of ecological overshoot. We can only address climate change by fully addressing ecological overshoot (Heinberg 2017; Herrington 2020).