«DIPLOMA THESIS Linking Climate Change with Food Security in the highlands of Khyber Pakhtunkhwa, Northwest Pakistan Presented by: Martin Kienzler ...»
For the future development of the South Asian summer monsoon REMO simulates a strong decrease of rainfall, using the SRES scenario A1B. Rupa Kumar et al. (2006) state a negative precipitation development for the same period (2071 to 2100) for Pakistan’s monsoon region, too. They revert to the scenarios A2 and B2. The extent of reduction is approximately the same as REMO simulates and amounts up to 15 to 20% of mean summer precipitation. For the monsoon aﬀected areas of India they in contrast project increasing summer rainfalls. Simulations with the help of PRECIS (scenario A2) result in negative precipitation trends in Pakistan’s monsoon aﬀected areas of up to 10% (Sheikh et al., 2010). Another regional climate model, namely COSMO-CLM also projects a distinct reduction of summer monsoon until the end of the 21st century for all of the three scenarios B1, A1B and A2 (Dobler & Ahrens, 2011). South of the Himalaya monsoon precipitation could be reduced by more than 30% per century.
However they claim the intensity of precipitation to increase. Ashfaq et al. (2009) project a further weakening of the South Asian summer monsoon and an associated reduction of precipitation amounts during the summer months until the end of the 21st century (scenario A2), as well as a weakening of the local Hadley circulation. This “monsoon suppression” also will become obvious through a delay of monsoon onset dates by two to four pentads, relative to the period 1961 to 2000. Besides a northwestwards shift of the low pressure during monsoon season and an associated shift of high precipitation into northwestern Pakistan is predicted (Rasul, 2011; Khan & Iqbal, 2011) Climatological means vs. extreme events An interesting point furthermore is that the informants around Chitral reported both, an increase of drought periods as well as an increase of events with heavy rainfall. This agrees with Chaudhry et al. (2009), who found a distinct incline of heat wave days for northern Pakistan and a decline of cold wave days, too. Similarly ul Islam et al. (2009) projects an increasing frequency of warm spells during the 21st century for northwestern Pakistan.
This is raising the question which climatic parameters generally are more important when analysing agricultural vulnerability: mean values or extreme events. According to Porter & Semenov (2005) changes in the mean temperature as well as the variability
Chapter 7. Discussion
of temperature can eﬀect crop processes, even though not the same ones. For example growth and development processes have temperature optima and show slowly decreasing productivity when mean values exceed these optima (Porter & Semenov, 2005;
Hussain & Mudasser, 2007). In contrast temperature thresholds can be eﬀective in very short time periods and “extensively damage yield productivity” (Porter & Semenov, 2005). Since climate generally tends to adapt both, higher mean values and a higher variability, crops show decreasing yields and are suﬀering damaging events more frequently. ul Islam et al. (2009) claim that changes in frequency and intensity of extreme temperature events are more important for agriculture than the variability of mean values. He arguments that a considerable number of extremely hot days would cause more damage to the crops than an increase in overall temperatures. Similarly Tubiello et al. (2007) points out that the increasing frequency of extreme events in general is “likely to increase production losses beyond those estimated from changes in mean variables alone”. It is however important in which speciﬁc development stage of the respective crop plant which kind of extreme event occurs, for example the transgression of certain temperature thresholds during ﬂowering.
Monsoon circulation contains a high risk of extreme precipitation events. These are especially dangerous for agriculture in mountainous regions due to the risk of landslides (Rasul, 2011). Therefore he concludes that short periods of extreme climate are much more important for agriculture than average values. Furthermore Wang et al. (2011) claim a steady increase in frequency of heavy precipitation events in the premonsoon trough phase during July, which are triggered through a “persistent increase in conditional instability” during this season. They relate this observation with a long-term process of changing circulation patterns in the region due to a “warming and moistening of the lower troposphere”. This is supported by Christensen et al. (2007) who predict “a general increase in the intensity of heavy rainfall events” for the next century and for northern Pakistan.
Considering the fact, that an increase of temperatures still is rather beneﬁcial for cropping above a certain altitude, even though up to a certain degree, and that summer temperatures in some parts of the region rather show regressive trends extreme events such as periods with hot temperatures and especially heavy precipitation events are likely to aﬀect the agriculture in the mountain regions of Khyber Pakhtunkhwa at a greater extent than the change of climate averages.
8 Conclusion and outlook This thesis studied the characteristics of climate change in the remote mountain areas of Khyber Pakhtunkhwa in northwestern Pakistan and the possible impacts of temperature and precipitation changes on agriculture, which is the mainstay of food security in these rural areas. Up to date there are not many studies which were dealing with this topic in this special region. But nevertheless the results of this thesis could be compared with the few existing results of other analyses. It can be aﬃrmed that the ﬁndings described before are in good accordance with the diﬀerent studies. This chapter summarizes the results of the thesis and gives an outlook to further research.
Characteristics of climate change in Khyber Pakhtunkhwa and its impacts on agriculture Climate change is distinctly visible in Khyber Pakhtunkhwa, too, during the twentieth century comparable to the most regions of the globe. But across the region the characteristics of climate change diﬀer strongly on a relatively small scale. This is mainly due to the highly diﬀerentiated relief of this high mountain region and the fact that several large-scale atmospheric circulation systems converge, especially the South Asian summer monsoon and western disturbances. Hence this interaction of extreme topography and complex climatology makes the climate of this region highly variable and the detection and future prediction of climate change quite challenging.
In general it can be said that northwestern Pakistan suﬀered only a slight warming during the twentieth century, compared with the global average. The temperature rise was strongest since the middle of the 1970s. For further conclusions the diﬀerent seasons had to be analysed separately. So it can be claimed that during the autumn and winter months a strong increase of temperatures within northwest Pakistan occurs. The increase is strongest in the high-mountain areas. Especially in altitudes above 1,500 masl, where for example maize and wheat are mostly grown as fodder plants because the growing season is too short for crops to reach maturity, a warming during winter and a shortening of the winter season is beneﬁcial. So fodder crops might be used for food purposes one time, which would enhance food security. In contrast the spring and summer months show a distinct negative temperature trend in most regions of Khyber Pakhtunkhwa. This cooling is quite unusual in a period of global warming and is mainly referred to the strong land use change, especially deforestation, which heavily occurs in the foothills of the Himalaya (Yadav et al., 2004). In contrast to the huge agricultural regions of the Indus and Ganges plains, where a strong temperature increase leads to a distinct reduction of crop yields, this cooling could help to reduce heat stress in the hot premonsoonal summer
Chapter 8. Conclusion and outlook
months and prevent yield losses. However a decrease of night temperatures in higher elevated areas could enhance the risk of damaging frost during the vegetation period.
The strong warming in winter compensates the negative temperature trend in summer and leads to an overall increase in annual mean temperatures, which however turns out to be comparatively slight.
Most parts of Khyber Pakhtunkhwa are directly dependent on the precipitation which occurs during the summer months and is triggered by the South Asian summer monsoon.
The results of the climate analysis show that monsoonal rainfalls generally succumb a high interannual variability but had a rather decreasing tendency during the last few decades. This reduction of monsoon rainfall is to a large extent related to diﬀerent human activities such as intensiﬁcation of agriculture, land-use changes, irrigation and emissions of aerosols (Niyogi et al., 2010; Saeed et al., 2009; Ramanathan et al., 2005). Furthermore precipitation events during the monsoon season now seem to be more erratic. Hence the higher frequency of heavy precipitation events could cause devastating ﬂoods in Pakistan like it happened in the years 2010 and 2011. On the other hand longer and more drought periods are recorded in between. Less precipitation amounts in general and more frequent drought periods during the vegetation period could lead to more drought stress for the plants. This moreover requires enhanced irrigation in regions, where agriculture cannot be conducted on an exclusively rainfed basis.
Some parts of Khyber Pakhtunkhwa, like the northwestern part around Chitral hardly receive any precipitation during the summer months because high mountain barriers insulate them from summer monsoon. Agriculture depends on artiﬁcial irrigation and winter rain. The latter is brought by western disturbances originating over the Atlantic Ocean. So precipitation variability in winter strongly depends on variations of the North Atlantic Oscillation (NAO) (Archer & Fowler, 2004). Climate analysis suggests that winter precipitation over the western parts of Khyber Pakhtunkhwa has an increasing tendency. This would mean an higher water supply in the valleys, where cropping is also possible in winter and more storage of water in the form of ice and snow in the high mountain areas. This in turn would cause enhanced water availability in spring and summer, when precipitation is insuﬃcient.
The combination of enhanced winter precipitation and reduced summer temperatures could cause a thickening of the mountain glaciers of the Hindu Kush and Karakoram (Hewitt, 2005) which is in stark contrast to glacier development around the globe. In the long term this situation might improve water availability.
The projected future situation Besides the simulations of the climate model REMO conducted in this thesis several studies tried to draw a projection for the climate of the region for the twenty-ﬁrst century. Both, the results obtained in this study as well as the results of the studies which were consulted for comparison predict a strong warming for all of Khyber Pakhtunkhwa
Chapter 8. Conclusion and outlook
until the end of this century. Temperatures are supposed to rise about +4◦ C to +4.5◦ C in the valleys between the high mountain ranges and at the foothills of the mountains.
Stronger warming will occur within the high mountain areas at higher elevations and amounts to more than +5.5◦ C in some parts. Besides warming is strongest in winter and spring for all parts of the region. The cooling tendency of the spring and summer months recorded for the last decades however does not appear at all in future simulations.
This might be because the land surface in REMO is static and human induced changes such as deforestation are not taken into account. This means that future projections are exclusively simulated with the greenhouse gas forcing as boundary value. The strong warming might have negative implications for agriculture in the regions at lower elevations. For the cropping areas in higher elevations the temperature threshold of +4◦ C, which Sultana et al. (2009) deﬁned as limiting value of beneﬁcial impacts of climate change in the humid mountainous areas, would be exceeded distinctly.
Most of the studies furthermore agree with the ﬁndings of this thesis concerning the development of precipitation. The simulations of the regional climate model REMO predict a further weakening of the South Asian summer monsoon, which means that summer rainfall is expected to suﬀer further reduction. Combined with a strong warming as projected for the twenty-ﬁrst century this could lead to intensiﬁed water scarcity and drought stress for the crops, even at higher altitudes. Furthermore precipitation is simulated to decrease all over the year. So less water can be stored as snow, which will aggravate the lack of water. In the regions that are not inﬂuenced by monsoon, summer precipitation is projected to be reduced, too, but only slightly. But due to the fact that here agriculture is only possible through irrigation anyway, these ﬁndings will even worsen the situation. In contrast winter precipitation is supposed to further increase distinctly in the regions north of the monsoon belt until 2100. This would be beneﬁcial for agriculture and water availability in spring, given the assumption that precipitation in winter furthermore falls as snow. Unlike in the monsoon aﬀected regions the increase in winter precipitation is going to compensate the reduction of summer rain, so that annual precipitation amounts are supposed to increase until the end of the century.
The local perception of climate change and its impacts The semi-structured interviews have shown that in most parts of the case studies yields have increased considerably during the last twenty to thirty years. However the people mostly relate the increase of their yields to technological improvements such as machines and irrigation, fertilizer and the improvement of the accessibility of the area combined with an increasing demand on the markets of the surrounding towns. Although the overall perception of the local people concerning climatic changes turned out to be quite good, only very few of the farmers related changes in yields to trends in mean climatology.