Spatially varying impacts of climate change on wheat and barley yields in Kazakhstan

Highlights

• We present the first empirical study of the impacts of climate change on wheat and barley yields for Kazakhstan.

• We accounted for the impacts of extreme heat because it can cause disproportionately large and sudden losses in crop yields.

• The negative impacts of climate change on yields in some areas are partly outweighed by small positive impacts in other areas.

• Our results are important for farmers, policy makers, and investors to targt adaptation strategies to climate change.

Abstract

Climate change has compromised global cereal production, particularly in semiarid regions where small changes in rainfall and temperature or excessive heat can have large effects on crop productivity. Central Asia is particularly vulnerable to climate change, but the understanding of the impacts of climate change on yields is incomplete for this region. We used fixed-effect panel regressions to quantify the impacts of climate trends on wheat and barley yields from 1980 to 2015 in the northern part of Kazakhstan, which is a globally important cereal-producing region. Our results suggest large spatial variations in the impacts of climate change on yields. Compared with the counterfactual situation without climate trends, the observed changes in climate reduced wheat and barley yields by 1.9% and 4.8%, respectively, in the primary cereal-producing region in the west of the study area. These negative impacts were partly compensated for by positive effects in the eastern part of the study region. Extreme heat events had little impact on wheat and barley yields. Suitable adaptation strategies include switching to more drought-resistant crops or to extensive livestock production in areas where climate change has negatively affected crop yields, and the expansion of cereal production in areas that have benefited from climate change.

Introduction

Climate change, which contributes to yield stagnation or yield declines in some major global breadbaskets (Ray et al., 2012), constitutes one of the greatest threats to food security in the 21st century (Wheeler and von Braun, 2013). In several key production regions, trends in temperature and precipitation since the 1980s have decreased crop yields relative to what would have been achieved without the observed climate trend (Lobell et al., 2011; Zhao et al., 2017). For example, wheat yields in Russia, a country with very high yield potentials (Schierhorn et al., 2014), would be almost 15% higher without these yield-limiting climate trends (Lobell et al., 2011). Identifying regions where crop yields are sensitive to the effects of climate change is paramount to developing efficient and timely adaptation strategies (Zhao et al., 2017).

Ample literature on the impacts of climate change on crop yields exists for many globally important breadbaskets (Challinor et al., 2014), but only a few studies are available for Central Asia (see, for example, Sommer et al., 2013; Porter et al., 2014; Reyer et al., 2015). This is unfortunate because Central Asia is already affected by and vulnerable to climate change (Reyer et al., 2015). Together with Alaska and North Asia, Central Asia experienced the strongest increase in average temperatures worldwide from 1901 to 2008 (Harris et al., 2014). Temperatures will likely continue to increase in Central Asia at a rate above the global average, leading to an increased frequency of heat stress and higher drought risk, which are of great concern considering the importance of agriculture for the economies of this region (Hijioka et al., 2014; World Bank, 2014). Moreover, a considerable share of the population live in rural areas and rely on agricultural production to secure their livelihoods (World Bank, 2014; Reyer et al., 2015). Given the low adaptive capacity of farmers to droughts and the high proportion of cereals in human diets (Fehér et al., 2017), decreasing cereal yields and increasing yield volatility may jeopardize food security in Central Asia (World Bank, 2014; Reyer et al., 2015). Unfortunately, critical knowledge on how observed climate changes impact agricultural production in Central Asia is missing (Hijioka et al., 2014).

Kazakhstan is by far the largest producer and exporter of cereals in Central Asia. This country was among the top ten wheat-exporting countries globally between 2000 and 2016. Kazakh grain is characterized by high protein and gluten contents due to the short and warm growing season and is thus highly competitive in international markets (Abugalieva and Peña-Bautista, 2010). Kazakhstan is extremely important for food security throughout Central Asia because more than 70% of the wheat imports of Central Asian countries originated from Kazakhstan in 2016 and 2017 (FAOSTAT, 2018; USDA, 2018a). In 2018, this country had the sixth largest area dedicated to wheat cultivation in the world (USDA, 2018b). However, crop yields in Kazakhstan are low due to unfavorable climate conditions (a short growing season with high temperatures and limited water availability) and low input use (fertilizers, pesticides, and water). Because farmers avoid the risk of losing investment costs for intermediary inputs in cases of complete shortfall due to drought (Sommer et al., 2013; Bobojonov and Aw-Hassan, 2014), low input use is driven primarily by the volatile climate conditions that cause yields and total production to fluctuate drastically from one year to another (Meyfroidt et al., 2016).

The average daily temperatures in northern Kazakhstan, the primary cereal-producing region of this country, have increased by 1.5 °C since 1901, with stronger warming in winter than in summer (Hijioka et al., 2014; Salnikov et al., 2015). Precipitation trends are characterized by stronger variability than are temperature trends, though both exhibited nonsignificant increasing (in the provinces of Pavlodar and North Kazakhstan) and decreasing (Akmola and Kostanay) trends in different parts of northern Kazakhstan during 1951–2010 (Hijioka et al., 2014; Salnikov et al., 2015). Furthermore, there is high agreement among models that temperatures will continue to increase in the future (Kirilenko and Dronin, 2011; Sommer et al., 2013), especially in spring (Wright et al., 2009). Future precipitation trends are more uncertain than temperature trends, but it is likely that northern Kazakhstan will become wetter in winter (Hijioka et al., 2014). However, extremely high temperatures and droughts will probably become more frequent in this region (Teixeira et al., 2013).

The impacts of climate change on crop yields can be estimated with process-based crop simulation models, which characterize crop growth primarily at daily time steps, or by statistical models, which predict yields using observed yields and historical weather records (Challinor et al., 2014). An important step towards better understanding the impacts of climate change on yields and developing efficient adaptation strategies is to assess the extent to which historical and recent crop yield trends have been affected by climate trends (Lobell et al., 2011). For instance, Mirzabaev et al. (2013) found a small net impact of weather variability from 1990 to 2010 on the crop production revenues in the northern part of Kazakhstan. However, to the best of our knowledge, studies of the impacts of historic and recent changes in climate conditions on yields are not available for Kazakhstan, despite the importance of this region to global grain markets. An important reason for this research gap has been the paucity of time series data for crop yields. Moreover, separating the potential effects of climate change on crop yields from the effects of socioeconomic and institutional changes is challenging (Sommer et al., 2013). In Kazakhstan, for example, shrinking state support for both producers and consumers as well as political and institutional uncertainties following the dissolution of the Soviet Union negatively affected input intensity and led to declining crop yields in the 1990s (Meyfroidt et al., 2016).

The primary objective of this paper is to quantify the impacts of changes in the average temperature, heat, and precipitation on wheat and barley yields from 1980 to 2015. We used fixed-effect panel regressions to compare counterfactual yields without climate change with the observed yields and actual climatic changes at the district level for the northern part of Kazakhstan, where more than 90% of Kazakhstan's wheat production originates. Our results provide the first fine-scale assessment of the impacts of climate change on cereal yields and can support farmers, policy makers, and investors in formulating spatially targeted adaptation strategies. Our insights are also valuable for advancing knowledge of the impacts of climate change on crop production in other arid and semiarid regions.