5.5.1 Autonomous adaptations
Many of the autonomous adaptation options identified before and since the TAR are largely extensions or intensifications of existing risk-management or production-enhancement activities. For cropping systems there are many potential ways to alter management to deal with projected climatic and atmospheric changes (Aggarwal and Mall, 2002; Alexandrov et al., 2002; Tubiello et al., 2002; Adams et al., 2003; Easterling et al., 2003; Howden et al., 2003; Howden and Jones, 2004; Butt et al., 2005; Travasso et al., 2006; Challinor et al., 2007). These adaptations include:
- altering inputs such as varieties and/or species to those with more appropriate thermal time and vernalisation requirements and/or with increased resistance to heat shock and drought, altering fertiliser rates to maintain grain or fruit quality consistent with the climate and altering amounts and timing of irrigation and other water management practices;
- wider use of technologies to ‘harvest’ water, conserve soil moisture (e.g., crop residue retention) and to use water more effectively in areas with rainfall decreases;
- water management to prevent waterlogging, erosion and nutrient leaching in areas with rainfall increases;
- altering the timing or location of cropping activities;
- diversifying income by integrating other farming activities such as livestock raising;
- improving the effectiveness of pest, disease and weed management practices through wider use of integrated pest and pathogen management, development and use of varieties and species resistant to pests and diseases, maintaining or improving quarantine capabilities, and sentinel monitoring programs;
- using seasonal climate forecasting to reduce production risk.
If widely adopted, these autonomous adaptations, singly or in combination, have substantial potential to offset negative climate change impacts and take advantage of positive ones. For example, in a modelling study for Modena (Italy), simple, currently practicable adaptations of varieties and planting times to avoid drought and heat stress during the hotter and drier summer months predicted under climate change altered significant negative impacts on sorghum (–48 to –58%) to neutral to marginally positive ones (0 to +12%; Tubiello et al., 2000). We have synthesised results from many crop adaptation studies for wheat, rice and maize (Figure 5.2). The benefits of adaptation vary with crops and across regions and temperature changes; however, on average, they provide approximately a 10% yield benefit when compared with yields when no adaptation is used. Another way to view this is that these adaptations translate to damage avoidance in grain yields of rice, wheat and maize crops caused by a temperature increase of up to 1.5 to 3°C in tropical regions and 4.5 to 5°C in temperate regions. Further warming than these ranges in either region exceeds adaptive capacity. The benefits of autonomous adaptations tend to level off with increasing temperature changes (Howden and Crimp, 2005) while potential negative impacts increase.
While autonomous adaptations such as the above have the potential for considerable damage avoidance from problematic climate changes, there has been little evaluation of how effective and widely adopted these adaptations may actually be, given (i) the complex nature of farm decision-making in which there are many non-climatic issues to manage, (ii) the likely diversity of responses within and between regions in part due to possible differences in climate changes, (iii) the difficulties that might arise if climate changes are non-linear or increase climate extremes, (iv) time-lags in responses and (v) the possible interactions between different adaptation options and economic, institutional and cultural barriers to change. For example, the realisable adaptive capacity of poor subsistence farming and/or herding communities is generally considered to be very low (Leary et al., 2006). These considerations also apply to the livestock, forestry and fisheries.
Adaptations in field-based livestock include matching stocking rates with pasture production, rotating pastures, modifying grazing times, altering forage and animal species/breeds, altering the integration of mixed livestock/crop systems, including the use of adapted forage crops, re-assessing fertiliser applications, ensuring adequate water supplies and using supplementary feeds and concentrates (Daepp et al., 2001; Holden and Brereton, 2002; Adger et al., 2003; Batima et al., 2005). It is important to note, however, that there are often limitations to these adaptations. For example, more heat-tolerant livestock breeds often have lower levels of productivity. Following from the above, in intensive livestock industries, there may be reduced need for winter housing and for feed concentrates in cold climates, but in warmer climates there could be increased need for management and infrastructure to ameliorate heat stress-related reductions in productivity, fertility and increased mortality.
A large number of autonomous adaptation strategies have been suggested for planted forests including changes in management intensity, hardwood/softwood species mix, timber growth and harvesting patterns within and between regions, rotation periods, salvaging dead timber, shifting to species or areas more productive under the new climatic conditions, landscape planning to minimise fire and insect damage, adjusting to altered wood size and quality, and adjusting fire-management systems (Sohngen et al., 2001; Alig et al., 2002; Spittlehouse and Stewart, 2003; Weih, 2004). Adaptation strategies to control insect damage can include prescribed burning to reduce forest vulnerability to increased insect outbreaks, non-chemical insect control (e.g., baculoviruses) and adjusting harvesting schedules, so that those stands most vulnerable to insect defoliation can be harvested preferentially. Under moderate climate changes, these proactive measures may potentially reduce the negative economic consequences of climate change (Shugart et al., 2003). However, as with other primary industry sectors, there is likely to be a gap between the potential adaptations and the realised actions. For example, large areas of forests, especially in developing countries, receive minimal direct human management (FAO, 2000), which limits adaptation opportunities. Even in more intensively managed forests where adaptation activities may be more feasible (Shugart et al., 2003) the long time-lags between planting and harvesting trees will complicate decisions, as adaptation may take place at multiple times during a forestry rotation.
Marine ecosystems are in some respects less geographically constrained than terrestrial systems. The rates at which planktonic ecosystems have shifted their distribution has been very rapid over the past three decades, which can be regarded as natural adaptation to a changing physical environment (see Chapter 1 and Beaugrand et al., 2002). Most fishing communities are dependent on stocks that fluctuate due to interannual and decadal climate variability and consequently have developed considerable coping capacity (King, 2005). With the exception of aquaculture and some freshwater fisheries, the exploitation of natural fish populations, which are common-property resources, precludes the kind of management adaptations to climate change suggested for the crop, livestock and forest sectors. Adaptation options thus centre on altering catch size and effort. Three-quarters of world marine fish stocks are currently exploited at levels close to or above their productive capacity (Bruinsma, 2003). Reductions in the level of fishing are therefore required in many cases to sustain yields and may also benefit fish stocks, which are sensitive to climate variability when their population age-structure and geographic sub-structure is reduced (Brander, 2005). The scope for autonomous adaptation is increasingly restricted as new regulations governing exploitation of fisheries and marine ecosystems come into force. Scenarios of increased levels of displacement and migration are likely to put a strain on communal-level fisheries management and resource access systems, and weaken local institutions and services. Despite their adaptive value for the sustainable use of natural resource systems, migrations can impede economic development (Allison et al., 2005; see Chapter 17, Box 17.8).