IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group III: Mitigation of Climate Change

8.5 Interactions of mitigation options with adaptation and vulnerability

As discussed in Chapters 3, 11 and 12, mitigation, climate change impacts, and adaptation will occur simultaneously and interactively. Mitigation-driven actions in agriculture could have (a) positive adaptation consequences (e.g., carbon sequestration projects with positive drought preparedness aspects) or (b) negative adaptation consequences (e.g., if heavy dependence on biomass energy increases the sensitivity of energy supply to climatic extremes; see Chapter 12, Subsection 12.1.4). Adaptation-driven actions also may have both (a) positive consequences for mitigation (e.g., residue return to fields to improve water holding capacity will also sequester carbon); and (b) negative consequences for mitigation (e.g., increasing use of nitrogen fertilizer to overcome falling yield leading to increased nitrous oxide emissions). In many cases, actions taken for reasons unrelated to either mitigation or adaptation (see Sections 8.6 and 8.7) may have considerable consequences for either or both(e.g., deforestation for agriculture or other purposes results in carbon loss as well as loss of ecosystems and resilience of local populations). Adaptation to climate change in the agricultural sector is detailed in (IPCC, 2007; Chapter 5).

For mitigation, variables such as growth rates for bioenergy feedstocks, the size of livestock herds, and rates of carbon sequestration in agricultural lands are affected by climate change (Paustian et al., 2004). The extent depends on the sign and magnitude of changes in temperature, soil moisture, and atmospheric CO2 concentration, which vary regionally (Christensen et al., 2007). All of these factors will alter the mitigation potential; some positively and some negatively. For example: (a) lower growth rates in bioenergy feedstocks will lead to larger emissions from hauling and increased cost; (b) lower livestock growth rates would possibly increase herd size and consequent emissions from manure and enteric fermentation; and (c) increased microbial decomposition under higher temperatures will lower soil carbon sequestration potential. Interactions also occur with adaptation. Butt et al. (2006) and Reilly et al. (2001) found that modified crop mix, land use, and irrigation are all potential adaptations to warmer climates. All would alter the mitigation potential. Some of the key vulnerabilities of agricultural mitigation strategies to climate change, and the implications of adaptation on GHG emissions from agriculture are summarized in Table 8.9.

Table 8.9: Some of the key vulnerabilities of agricultural mitigation strategies to climate change and the implications of adaptation on GHG emissions from agriculture

Agricultural mitigation strategies Vulnerability of the mitigation option to climate change Implication for GHG emissions of adaptation actions  
Cropland management – agronomy Vulnerable to decreased rainfall, and in cases near the limit of their climate niche, to higher temperatures. NO2 emissions would increase if fertilizer use increased, or if more legumes were planted in response to climate-induced production declines. 
Cropland management – nutrient management Only weakly sensitive to climate change, except in cases where the entire cropping enterprise becomes unviable. No significant adaptation to effects of climate change possible beyond tailoring of practices to ambient conditions. Therefore, additional GHGs not expected. 
Cropland management – tillage/residue management Sensitive to climate change. Higher temperatures could lower soil carbon sequestration potential. Warmer, wetter climates can increase risk of crop pests and diseases associated with reduced till practices. Adaptation not anticipated to have a significant GHG effect. 
Cropland management – water management Irrigation is susceptible to climate changes that reduce the availability of water for irrigation or increases crop water demand. Possible increase in energy-related GHG emissions if greater pumping distances or volumes are required. Adoption of more water-use efficient practices will generally lower GHG emissions. 
Cropland management – rice management Vulnerable to climate-change-induced changes in water availability. Low CH4 emitting cultivars may be susceptible to changes in temperature beyond their tolerance limits. Adaptation strategies are limited and not expected to have large GHG consequences. 
Cropland management – set-aside and land-use change Set-asides may be needed to offset loss of productivity on other lands. Adaptation is either to try to keep production high on non-set-aside land, which could increase GHG emissions, or return some set-asides to production. Increases in GHGs are in both cases fairly small, and less than the case of not having set-asides in the first place. They could be further mitigated by applying low GHG emitting practices in all cases. 
Cropland management – agro-forestry Large changes in climate could make certain forms of agro-forestry unviable in particular situations. Adaptation of practices and species used to less favourable climates could lead to some loss of CO2 uptake potential.  
Grazing land management/pasture improvement  Fire management can be impacted negatively or positively by climate change depending on ecosystem and sign of climate change. Extreme drying or warming could make marginal grazing lands unviable. Wetter conditions will promote conversion of grazing lands to crops. Increased fire protection activities can increase GHGs emissions by a small amount, thus reducing the net benefit obtained from reducing fire extent and frequency. 
Management of agricultural organic soils The mitigation measure is sensitive to increases in temperature or decreases in moisture, both of which would decrease the carbon sequestration potential.  Some trade-offs between CO2 uptake and CH4 emissions can be expected if the soils become wetter as a result of the adaptation management. 
Restoration of degraded lands  The sustainability of restored lands could be vulnerable to increased temperature and/or decreased soil moisture. Energy used to replant, or fertilizer used to increase establishment, success could lead to small additional GHG emissions 
Livestock - improved feeding practices, specific agents and dietary additives, longer term structural and management changes and animal breeding Weakly vulnerable to climate change except if it leads to the loss of viability of livestock enterprises in marginal areas or increased cost (or decreased availability) of feed inputs.  No general adaptation strategies. Specific strategies may have minor impacts on GHG emissions, for example, transport of feed supplements from distant locations could lead to increased net GHG emissions.  
Manure/biosolid management  Controlled waste digestion generally positively affected by moderately rising temperatures. Where GHGs are not trapped, higher temperatures could hamper management. If used as a nutrient source on pasture can increase CO2 uptake and carbon storage. 
Bioenergy – energy crops, solid, liquid, biogas, residues Particular bioenergy crops potentially sensitive to climate change, either positively or negatively. Areas devoted to bioenergy could be under increasing competition with the needs for food agriculture or biodiversity conservation under changing climate.  Generally, results in net CO2 uptake on land (apart from the fossil-fuel substitution). N2O emissions would increase if N turnover rates were greater than under previous land uses. Possible positive and negative impacts on net GHG emissions at various stages of the energy chain (cultivation, harvesting, transport, conversion) must be managed.