Estimating the Potential Role for Forests

In modeling the abatement forthcoming from different sectors, McKinsey (2007a) first estimated that to cap the long-term concentration of atmospheric CO2e at 450 ppm would require abatement of 26.7 Gt of CO2e by

BOX 1.5 WHAT ARE WE TALKING ABOUT IN FORESTRY OFFSETS: CARBON SEQUESTERED OR CARBON DIOXIDE REMOVED?

It is important that the difference between carbon sequestered and carbon dioxide in the atmosphere is recognized and made explicit when discussing emission trading, and particularly when it applies to forestry offsets. The following clarifies the relationship between carbon and carbon dioxide:

• The atomic weight of carbon is 12 and that of oxygen 16;

• The molecular weight of CO2 is thus 12 + 16 + 16 = 44;

• The molecular weight of CO2 is thus 44/12 that of carbon, i.e. 3.67.

When land is cleared of trees, and they rot or are burned, carbon is released as the greenhouse gas CO2.

When deforestation is prevented, C continues to be sequestered and CO2 emissions are avoided.

When trees are planted, every tonne of C sequestered through photosynthesis removes 3.67 tonnes of CO2 from the atmosphere. When an emission in one place or at one time is countered by removal by tree growth elsewhere or at another time, this is a forestry 'offset'.

2030; that is a 45 percent reduction in emissions compared with business as usual. McKinsey (2007a) then modeled the least-cost combination of abatement by sector in contributing to this target which, it was found, could be achieved at a market price of €40 per tonne of CO2e. Such modeling can be characterized as 'top down', in contrast to 'bottom up' that builds global estimates from regional studies. In allowing unfettered competition across all sectors to generate a least-cost portfolio of mitigation strategies, top-down models tend to simplify the options available.

McKinsey's (2007a) global model found that many abatement initiatives have a negative cost, including building insulation, fuel efficiency in vehicles, lighting, air conditioning and water heating, together with biofuel production from sugar cane. At low prices for carbon some forestation becomes feasible followed by greater potential for more forestation and avoided deforestation as the price of CO2e rises.

Abatement activity

Timing of impact: Impact change in carbon sequestered over time

Timing of cost: $ expenditure over time

Plant new forests

Increase sink

Prevent deforestation

Reduce emissions

Sustainable forest

Increase sink

managementa Suppress disturbances,13 reduce logging impact

Reduce emissions

X

a Sustainable forest management includes the replanting of forest after harvesting to speed up regeneration and adoption of longer rotations between harvesting. b The suppression of disturbances aims to reduce the gradual degradation of forests due to such factors as use of forests for fuelwood.

Notes:

a Sustainable forest management includes the replanting of forest after harvesting to speed up regeneration and adoption of longer rotations between harvesting. b The suppression of disturbances aims to reduce the gradual degradation of forests due to such factors as use of forests for fuelwood.

Figure 1.4 Generalization of the timing of impacts and costs in forestry sector abatement of carbon emissions

In achieving the 26.7 Gt reduction in emissions, the potential contribution of forestry was larger than for any other sector studied. Some 35 percent of all potential abatements involved forestry, which contributes an abatement of 6.7 Gt (see Figure 1.5). At the price of €40 per tonne of CO2e, deforestation rates were reduced by 50 percent in Africa and by 75 percent in Latin America, generating 3 Gt of annual abatement by 2030. Major abatement in Asia costs more since commercial logging there has a higher opportunity cost than subsistence farming in Africa and commercial agriculture in Latin America.

Other top-down modeling exercises produced similar estimates of abatement and offset potential by forestry. The IPCC (Nabuurs et al., 2007) synthesized the results from three global sector models to derive forestry's potential by region and by type of activity (Sohngen and Sejdo, 2006; Sathaye et al., 2006; Benítez et al., 2007). Table 1.3 summarizes the results for a price of CO2e of US$50 per tonne. The results in Figure 1.5 and Table 1.3 are not directly comparable as, at the time of writing, €40 = US$61.8. Nevertheless, there is broad agreement between the studies, the IPCC synthesis providing an estimated global abatement potential of almost 9.6 Gt CO2e compared with McKinsey's (2007a) estimate of 6.7. The studies agree that deforestation in Africa and Central and South America is an important source of abatement. Table 1.3 also shows that

TRANSPORTATION Fuel efficient vehicles; Biofuels

BUILDINGS Efficient lighting, appliances Heating cooling efficiency; Insulation

MANUFACTURING Industrial carbon capture and storage Fuel switching e.g. biofuels Energy efficiency e.g. cogeneration

POWER

Carbon capture and storage Nuclear Renewables

AGRICULTURE/WASTE No-tillage agriculture Methane capture from landfills

FORESTRY Afforestation/reforestation Deforestation avoided

Source: McKinsey (2007a).

Figure 1.5 Global potential for abatement by sector, at price = or < €40lt CO2e, GtCO2e per year by 2030

afforestation is also an important contributer to abatement in the US and in countries in transition. If the price of CO2 rises to US$100 in the top-down models, then the potential global abatement from forestry rises by 40 percent to almost 14 Gt CO2e by 2030 (Table 1.3).

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