Climate change has aptly been described as humankind’s greatest moral and technical challenge. A recent World Bank report predicts that more than 800 million people reside in areas that by 2050 will become dangerous climate hotspots (World Bank, 2018). If climate change causes a 3°C increase in average surface temperatures by 2100 (which is the expectation on our current trajectory) it is estimated to result in the extinction of 3 in every 5 species currently living (Flannery, 2008). Other studies (Thomas, et al., 2004), on the basis of mid-range climate-warming scenarios (temperature increases of 1.8–2.0°C for 2050, indicate that 15–37% of species in a representative sample of regions and taxa will be ‘committed to extinction’. At higher levels of temperature increase (>2°C) and where there are limited options for migration the extinction prediction increased to 38–52%. These dramatic extinction events are due to the relatively rapid rate of this change which does not allow these species to genetically adapt quickly enough. Loss of migratory pathways further prevents many from moving to compatible ecological zones at higher latitudes.

However, as emphasised by Dr Robert Glasser,[1] and the World Bank report authors themselves, presentation of the individual impacts of climate change do not adequately portray the full impact of climate change due to the “cascading” effects which are likely to be far more harmful than the immediate impacts. These cumulative impacts are difficult to accurately quantify.

Figure 1 Current net emissions trajectory vs. that required to meet 2050 target of 1.5°C temperature rise (World Resources Institute, 2018)

It is impossible to predict the impact on humans of large-scale species loss, in a world in which we are intimately dependent upon plants, animals, insects and microbes for our food and oxygen; if their destruction alone is not enough cause for alarm.

Never before has an environmental phenomenon been scientifically studied as carefully and thoroughly as climate change. Yet its complexity and the existence of many positive feedback loops[4] make it a difficult event to model and predict. Many scientists are expressing concerns that these positive feedback loops may lead to a tipping point causing climate change to escalate at such a pace that human efforts, no matter how strenuous, will no longer be able to halt its progress (Curtin, 2018).

Figure 2 Global warming trajectory: No change vs. Current commitment vs. Paris goal (World Resources Institute b., 2018)

Estimates of the global emissions outcome of current nationally stated mitigation ambitions (as submitted under the Paris Agreement) would lead to global greenhouse gas emissions in 2030 of 52–58 Gt CO₂eq yr^-1  [5] (see Figure 1). Analysis reflecting these ambitions indicate they would not limit global warming to 1.5°C, even if supplemented by very challenging increases in the scale and ambition of emissions reductions after 2030 (IPCC, 2018). Instead our current trajectory is for a 2.7 - 3.7°C increase in average surface temperature (see Figure 2).

As can be seen in Figure 3 below, New Zealand’s net emissions under the United Nations Framework Convention on Climate Change (UNFCCC) were 56.0 Mt CO₂-e in 2016 and emissions per person were the sixth[6] highest at 17.4 tonnes CO₂-e per capita amongst developed countries (NZ MFE, 2018).

Figure 3 Comparison of per capita CO2 equivalent GHG emissions in 2016 (NZ MFE, 2018)

By planting 1 billion additional trees over the next 10 years New Zealand can expect to sequester approximately 450 Mt CO₂ equiv. (author’s calculations) based upon the current target to plant two thirds native trees and one third exotics. This will buy only 8 years emissions at the current annual net emission rate of 56 Mt CO₂ equiv. Even if New Zealand is able to reduce its existing annual emissions (in order to extend the benefit of these carbon offsets), these offsets (if in the form of commercial plantations) will themselves produce increased emissions in their maintenance, harvesting, processing and transporting. This is discussed in Section 5 below.

[1] Visiting Fellow at the Australian Strategic Policy Institute and is the former UN Special Representative of the Secretary General for Disaster Risk Reduction.

[2] The earth is already committed to a 1.3°C increase; a delayed impact of our emissions to date (Flannery, 2008).

[3] 2017 "Syria Regional Refugee Response – Overview". UNHCR Syria Regional Refugee Response. 2017

[4] For example retreating polar icecaps reduce the overall reflection of sunlight from the earth’s surface and thus cause greater heat absorption (Flannery, 2008).

[5] 1 giga-tonne is one billion (1,000 million) tonnes.

[6] In 2017 New Zealand’s nearest neighbour Australia ranked 1^st at about 23.97 tonnes CO₂-e per capita (OECD, 2017)