Food and environment

The impact of climate change can be considered as the baseline (or business as usual) scenario. It provides a reference for what will happen under climate change if no adaptation measures are taken. The simulated changes for the periods 2010-2039 and 2070-2099 are compared with the current situation represented by the period 1960-1990. For this, the SWAP model has been used for calculating

Table 10.2. Effects table to assess the impact of a certain adaptation strategy. Indicator values express the change as a percentage relative to the baseline period 1961-1990.

Indicator

Adaptation

Food

Environment

(%)

Quantity Security (% change)

Quantity Security (% change)

No adaptation

2010-2039 +0 2070-2099 +0

+0 +0

6 -27

10 -8

28 -7 78 13

Food adaptation

2010-2039 +10 2070-2099 +10

+ 10 + 10

19 42

-8 -8

-15 -20 28 -3

Environment adaptation

2010-2039 -10 -10 2070-2099 -10 -10

-9 -10 -

14 11

85 17 137 17

changes in food indicators at the field scale, whereas the WSBM model has been run to quantify changes in hydrology and consequently in basin-wide food production and the environment.

changes in food indicators at the field scale, whereas the WSBM model has been run to quantify changes in hydrology and consequently in basin-wide food production and the environment.

Figure 10.4 shows the impacts of climate change on food security. Crop yields will increase as a result of the enhanced CO2 levels and the somewhat higher precipitation. However, at the same time a substantial increase in variation in yields is expected. But overall, the impact of changes in climate on food production levels is positive.

Outflow to the sea, used as the environmental indicator here, shows a somewhat similar picture, although the variation is much higher than seen for crop yield and total production (Fig. 10.4). However, if we consider the number of years that the minimum flow requirements are lower than the defined required one of 100 X 106 m3, the situation is expected to change positively. In the period 1961-1990, minimum flow requirements were not met in 26% of the years. This changed to 33% and 13% for 2010-2039 and 2070-2099, respectively.

Overall, the impact of climate change appears to be positive from a water resources, food production and environmental point of view for Walawe Basin. However, if we take a somewhat closer look at the extremes in yield and productivity, there is some reason for concern. It is known that farmers are very vulnerable to extremes and especially the number of consecutive years of low yields. Farmers might be able to cope with 1 low-yield year, but 2 or even 3 consecutive years might be hard. There is the tendency that in the future the number of consecutive low-yield years increases. Figure 10.5 shows clearly that a clustering of extremes can be expected and coping strategies will be required to deal with this.

500,000-

400,000-

200,000-

100,000-

1961-1990 2010-2039 2070-2099

co 800 0

J 400

co 800 0

J 400

1961-1990 2010-2039 2070-2099

Fig. 10.4. Impact of climate change on total rice production (left) and outflow to the sea (right) using the HadCM3_A2 projection.

Fig. 10.5. Years in which total rice production is at least 5% lower than the 5-year moving average.

Adaptation Strategies

The overall impact of climate change on food production and environmental quality, as described in the previous section, appears to be positive. However, while the long-term average food situation is improving, variation in yield is increasing. Similarly, mean outflow to the sea is higher, but variation is also on the rise. Besides this externally driven climate change, the internal changes in the basin as described in the beginning of this chapter will put more stress on water resources, resulting in a reduced amount of water available for food production and the environment.

These external stressors include that more food will be required to feed the growing population in the basin as well as in the capital Colombo. There will also be increased demand for industrial domestic and environmental use. Simultaneously, there will be a growing pressure on land as more land is required for industry, urban use and service-oriented activities such as tourism.

To overcome these negative impacts of climate change and internal stressors on water resources, adaptation is required. Several attempts to generate a list of adaptation strategies have been undertaken, but no conclusive strategies have been developed. A nice example showing that defining adaptation strategies is not straightforward is shown by the Canadian Climate Impacts and Adaptation Research Network (CCIARN, 2002), which claims that 'priority setting' is the main issue. This was confirmed by a review of Smith et al. (2001), who stated that many different types of adaptation measures might be employed. Carter (1996) stated that possible adaptations are based on experience, observation and speculation about alternatives that might be created and they cover a wide range of types and can take numerous forms (UNEP, 1998). It is important to make a distinction between the different players as to who can do what (Droogers et al., 2002).

The main problem facing the development of adaptation strategies is the level of detail included in the proposed strategies. Considering the problems expected in Walawe Basin it is clear that, although small and minor adaptation strategies might have some impact, we have to concentrate on basin-wide overall water resources issues. To address these issues two types of adaptation strategies can be considered: (i) a possible change in the total amount of water used for irrigation; and (ii) a change in the total cropped area in the basin. These two strategies were included in the overall analysis framework as developed for the basin and results will be discussed in the next section.

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