Decadal analysis of impact of future climate on wheat production in dry Mediterranean environment: A case of Jordan

https://doi.org/10.1016/j.scitotenv.2017.07.270Get rights and content

Highlights

  • Decadal impact of climate change on wheat yield was assessed in Jordan.

  • Future wheat yield due to climate change will increase in Jordan and in similar dry Mediterranean environment.

  • Elevated CO2 levels negate the adverse impact of climate change on wheat yield.

  • Reduced crop cycle offers opportunity to deploy longer duration varieties that may yield more.

Abstract

Different aspects of climate change, such as increased temperature, changed rainfall and higher atmospheric CO2 concentration, all have different effects on crop yields. Process-based crop models are the most widely used tools for estimating future crop yield responses to climate change. We applied APSIM crop simulation model in a dry Mediterranean climate with Jordan as sentinel site to assess impact of climate change on wheat production at decadal level considering two climate change scenarios of representative concentration pathways (RCP) viz., RCP4.5 and RCP8.5. Impact of climatic variables alone was negative on grain yield but this adverse effect was negated when elevated atmospheric CO2 concentrations were also considered in the simulations. Crop cycle of wheat was reduced by a fortnight for RCP4.5 scenario and by a month for RCP8.5 scenario at the approach of end of the century. On an average, a grain yield increase of 5 to 11% in near future i.e., 2010s–2030s decades, 12 to 16% in mid future i.e., 2040s–2060s decades and 9 to 16% in end of century period can be expected for moderate climate change scenario (RCP4.5) and 6 to 15% in near future, 13 to 19% in mid future and 7 to 20% increase in end of century period for a drastic climate change scenario (RCP8.5) based on different soils. Positive impact of elevated CO2 is more pronounced in soils with lower water holding capacity with moderate increase in temperatures. Elevated CO2 had greater positive effect on transpiration use efficiency (TUE) than negative effect of elevated mean temperatures. The change in TUE was in near perfect direct relationship with elevated CO2 levels (R2 > 0.99) and every 100-ppm atmospheric CO2 increase resulted in TUE increase by 2 kg ha 1 mm 1. Thereby, in this environment yield gains are expected in future and farmers can benefit from growing wheat.

Graphical abstract

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Transpiration use efficiency (kg ha 1 mm 1) of wheat yield production for baseline and decadal future climate based on RCP4.5 and RCP8.5 climate change scenarios, with and without considering CO2 response, at Maru and Mushaqar, Jordan. Year 2015 represents 2010–2020 decade, year 2025 represents 2020–2030 decade and so on.

Introduction

The phenomenon of climate change has a great impact on the global and regional crop production. The trends of climate have been fairly rapid in many agricultural regions around the world especially, over the past few decades along with the increases in atmospheric carbon dioxide (CO2) concentration levels. Its impact on food security (FAO et al., 2013) is virtually certain as the aggregate productivity of global agriculture will be affected (Lobell and Gourdji, 2012). Changes in air temperature, seasonal rainfall patterns and atmospheric CO2 concentration are key drivers of the responses of crops to climate change and expected to affect crop production worldwide (Hatfield et al., 2011, Ludwig and Asseng, 2006). All these drivers have different effects on plant production and crop yields. In combination, these effects can either increase or decrease plant production and the net effect of climate change on crop yield depends on interactions among these factors. While the impact of climate change through increased temperatures and decreased and erratic rainfalls (IPCC (Intergovernmental Panel on Climate Change), 2007, IPCC (Intergovernmental Panel on Climate Change), 2014) is often negative, except in regions of high latitudes where temperatures are below the optimal range for wheat and impact is often positive (Mariani, 2017), the impact of elevated CO2 may increase plant production and yield due to higher rates of photosynthesis and increased transpiration use efficiency through reduced transpiration (Amthor, 2001, Kimball et al., 1995, Long et al., 2004, Singh et al., 2014b, Sommer et al., 2013). This could partially negate the detrimental effects of rising temperatures depending on the degree of the temperature rise and the extent of reduction in crop transpiration under elevated CO2 (Singh et al., 2014a) especially, for C3 crops like wheat (Leakey et al., 2006).

Over the next few decades, CO2 trends will likely increase global yields by roughly 1.8% per decade. At the same time, warming trends are likely to reduce global yields by roughly 1.5% per decade without effective adaptation, with a plausible range from roughly 0% to 4% (Lobell and Gourdji, 2012). Global wheat production is estimated to fall by 6% for each °C of further mean temperature increase (Asseng et al., 2015). While the effects of climate change will vary greatly depending on region, at a global level however, Lobell et al. (2011) estimated that rising temperatures since 1980 have already lowered wheat yields by 5.5% without considering the effect of increasing CO2 levels and by 2.5% considering CO2 fertilization. As the impacts of climate change on crop production are going to vary from region to region (McGrath and Lobell, 2013), there is a need to conduct an analysis to assess the climate change impact on the region and crop of our interest.

Crop modeling studies driven by long-term daily weather data can predict the impact of climate-induced risk on crop productivity (Dixit and Telleria, 2015, Webber et al., 2014). Indeed, the most widely used tools available for estimating future crop yield responses to climate change are process-based crop models, and these are already applied extensively in different parts of the world (Challinor et al., 2014, Grossman-Clarke et al., 2001, Ortiz et al., 2008, Pirttioja et al., 2015, Rosenzweig et al., 2012, Rosenzweig et al., 2014, White et al., 2011). Crop simulation models have been applied to provide answers to practical production questions. For example, Ludwig and Asseng (2006) found that interactions between CO2, temperature, and rainfall were not linear and their effects on wheat yields varied with soil type and geographical locations (Cammarano et al., 2012). Numerous crop modeling studies have been conducted over the last few decades to observe the impact of climate change on crop yield of wheat and other crops (Anwar et al., 2015, Araya et al., 2015, Cammarano et al., 2012, Luo et al., 2005, Luo et al., 2009, O'Leary et al., 2015, Singh et al., 2014a, Singh et al., 2014b; and Yang et al., 2014). Some studies consider the combined impact of future climate and atmospheric CO2 while some ignore the CO2 fertilization effect altogether (Lobell et al., 2008). Most of the studies assess the impact of climate change either for a certain time slice e.g., 2050 or 2080 or current-near future (2010–2039), mid future (2040–2069) and the end of century (2070–2100) and do not expand the studies to decadal level i.e., assessing climate change impact along with CO2 for each decade until the end of century based on climatic variables and CO2 concentration for each decade. Often the information lacks on the nature and magnitude of the impact of potential climate change scenarios at the local level and on the best strategies and crop management which can be practiced to effectively adapt to climate change (Cammarano et al., 2012). The region of our interest is the dry Mediterranean climate in countries of the Middle East and North Africa (MENA) with sentinel sites in Jordan. Only one study (Al-Bakri et al., 2011) conducted climate change impact on rain-fed agriculture in Jordan but they did not consider effect of CO2. Special Report on Emissions Scenarios (SRES) (Nakicenovic et al., 2000) of Intergovernmental Panel on Climate Change (IPCC) projects higher global warming and reductions in growing season rainfall especially, in Mediterranean type environments (Luo et al., 2005). Rainfed agriculture is likely to be the most sensitive sector to climate change in Jordan where wheat is the main rainfed field crop in areas that receive > 350 mm rainfall for both local farmers and Bedouins (Al-Bakri et al., 2011) along with neighboring northern Syria which lie in the eastern Mediterranean region of MENA that is a prime example of the subtropical dry areas of the world (Ryan et al., 2006). In fact, across MENA, wheat (Triticum aestivum L. and Triticum turgidum ssp. durum) is the main staple food and wheat-based cropping systems dominate the zone delineated by the 350–600-mm isohyets (Moeller et al., 2014). Indeed, Jordan encourages wheat production through a price subsidy to producers as there is a wide gap in wheat demand and production and there are projects to enhance food security that focus primarily on improving wheat production and yield in wheat-based agricultural systems and hence the wheat production is very important for food security in this region (Al Hiary et al., 2015). According to the trade ministry of Jordan, Jordan imports over 96% of its wheat needs as domestic production covers only around 4% of demand. (Source: http://www.albawaba.com/business/grain-jordan-import-654790. Accessed 17 November 2015). Looking at the trend of wheat production since 1961, the average wheat production between the decade of 1961–70 was 147,540 with an average productivity of 612 kg ha 1. Historically, the Government of Jordan has encouraged technology adoption among farmers through several means including use of improved seed varieties, agro-techniques, water harvesting techniques, integrated pest management along with extension and support to minimum guarantee prices (Momany, 2001). Since the 1970s several national and international institutions, including the Ministry of Agriculture, the Arab Center for Studies of Arid and Dry Lands (ACSAD), and the International Center for Agricultural Research in the Dry Areas (ICARDA), introduced national breeding programs using adapted foreign wheat varieties to promote use of improved seed varieties. Due to these interventions, while the average wheat grown area has declined from 238,449 ha in 1961–70 to 20,100 ha in the 2005–2014 period, the average productivity has increased to 1068 kg ha 1 with a total average wheat production of 21,671 tons in 2005–2014 period. (Source: FAOSTAT online database, 2017. Available at http://www.fao.org/faostat/en/?#data/QC).

Hence it makes sense to assess the impact of future climate on wheat production particularly in Jordan, which also represents the MENA region with a dry Mediterranean climate. Soils with different water holding capacities may affect wheat yield differently (Luo et al., 2009, Yang et al., 2014) and so may the sites with different precipitation and soil water levels (Kimball et al., 1995, Long et al., 2004, Mitchell et al., 2001, Sommer et al., 2013, van Ittersum et al., 2003). The degree of reduction in transpiration due to elevated CO2 is another variable which will impact the yield and water requirement of crops (Ludwig and Asseng, 2006, Singh et al., 2014a, Sommer et al., 2013). Looking at the above, it appears important to assess the impact of climate change on wheat production in this environment especially, including the effect of elevated CO2 due to climate change. Most of the previous researchers have used SRES scenarios and climate data from general circulation models (GCMs) utilized in the Fourth Assessment Report (AR4) of (IPCC, 2007). However, these have been recently superseded by the representative concentration pathways (RCPs) scenarios (IPCC (Intergovernmental Panel on Climate Change), 2014, Meinshausen et al., 2011, van Vuuren et al., 2011) and climate data from GCMs used in Coupled Model Intercomparison Project Phase 5 (CMIP5) described by Taylor et al. (2012) (more details in Materials and methods section). This warrants an updated climate change impact study on wheat production in this region. In this view, the objectives of this study are to i) assess the decadal impact of climate change in dry Mediterranean environment with two sentinel sites in Jordan ii) analyze the impact difference in soils with high and low water holding capacity and iii) if the future climate is favorable due to CO2 effect, evaluate the extent of yield benefits and improvement in transpiration use efficiency in this environment.

Section snippets

Study sites

Two sites in Jordan were selected viz., Maru (32.55°N, 35.85°E, Altitude 620 m) and Mushaqar (31.77°N, 35.77°E, Altitude 790 m). Wheat is grown in these sites and the Field Crops Research Department of the National Center for Agricultural Research and Extension (NCARE), Jordan has maintained its research stations at these sites. Maru site is characterized as the heavy clay soil type whereas Mushaqar site is characterized as the clay loam soil type representing sites with higher and lower water

Mean annual and seasonal rainfall

Mean annual and seasonal rainfall were computed from the 99 realizations of the weather for a given climate change (CC) scenario. The simulations for year 2015 represent the 2010s decade (2010  2020) and the last decade of this century i.e., 2090s or 2090–2100 is represented from the simulation of year 2095. At Maru: a higher decrease in mean rainfall, both annual and seasonal, is observed for RCP8.5 scenario than RCP4.5 scenario for a given future decade (Table 1, Fig. 2). For RCP4.5 scenario,

Conclusions and way forward

Considering the similar results of other studies on the impact of climate change, as mentioned above, APSIM appears to perform well in crop cycle, yield and transpiration use efficiency simulation of wheat at decadal level based on two prominent climate change scenarios viz., RCP 4.5 and RCP8.5. This study indicates that without considering the atmospheric CO2 concentration, the future climate will negatively impact wheat yield in Jordan and in dry Mediterranean environments with similar

Acknowledgements

The authors acknowledge the CGIAR Research Program on Policies, Institutions and Markets (PIM) led by the International Food Policy Research Institute (IFPRI) for providing funding for this research as a part of the Global Futures & Strategic Foresight (GFSF) Project (Grant No. 2015X440ICA). Support and help by Dr. Aden Aw-Hassan, Director, Social, Economic and Policy Research Program, ICARDA and Dr. Keith Wiebe, Senior Research Fellow at IFPRI is duly acknowledged. The views expressed here

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