1. Introduction
Agriculture is one of the most climate-sensitive sectors of an economy. It responds to temperature, precipitation, soil radiation, etc., which are directly associated with climate change. Rising temperature, uneven distribution of precipitation, floods, droughts, and other climatic disasters have affected human life along with socio-economic sectors of the world’s over-populated regions, i.e., South Asia [
1]. The assessment of the ultimate economic effect of climate change on producers, consumers, and other agriculture-related agents requires a detailed evaluation of economic impacts using inputs from a different climate and crop models.
To study the potential impacts of changing climate, scientists and crop experts carried out integrated and collaborative research [
2]. They have used global climate models that analyze the interaction of weather variables using different physical, biological, and chemical principles and then estimate their responses to rising levels of greenhouse gas emissions in the atmosphere. These models also consider different socio-economic projections, including income and population growth, energy use, and industrial growth to predict earth’s future climate. These global climate projections are then used by bio-physical scientists in different crop models to simulate biological processes of crop growth and productivity [
3,
4,
5,
6,
7,
8,
9,
10,
11,
12,
13]. They provide the estimated impact of climate change on crop yield and human health. These models overcome the requirement of time-consuming and expensive field surveys and experimentation to analyze the effects of weather variability on agriculture. Moreover, they can be easily used with different economic models to study the economic impacts of climate-induced- change in crop production. Two most commonly used models are DSSAT (Decision Support System for Agrotechnology Transfer) and APSIM (Agricultural Production Systems Simulator) [
14,
15,
16]
The potential impact of weather conditions on crop production through biophysical models can be used as input in different partial and general equilibrium economic models to analyze the economic response of climate change by different socio-economic agents of society (
Figure 1). In this paper, we only focus on the economic component of assessment by investigating the future endogenous economic response of agriculture to climate change scenarios of 2050. This includes agricultural production, crop yield, area, price, and consumption patterns. Moreover, the output and cost of other related industries are discussed.
Climate change has long-lasting impacts on the livelihood of agricultural communities across the world (Burke and Emerick, 2016) [
17]. The fifth annual report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) states that mean yearly temperature of South Asia will increase by 3.3 ºC by the end of 21st century under Multi-Model Data (MMD)-A1B regional climate model. A significant amount of research portrays the poor state of the agriculture sector of South Asian economies, due to extreme climate events [
1,
18,
19]. This sector will have difficulty providing food security to the rising population of the region. As more than 60% of the total population is involved in agricultural activities., loss of agricultural production, due to climate change is of serious socio-economic concern.
Pakistan is one of the most climate-sensitive nations despite the fact that it contributes merely 0.8% to atmospheric Greenhouse Gases (GHG), which places Pakistan at the 135th position in comparison to the other countries [
20]. Global climate risk index 2017 ranks Pakistan at number 7 in the list of most vulnerable nations, due to its geographical and climatic features. It lies in the geographic region where an increase in temperature is predicted to be higher than global average temperature, where glaciers, the only source of feeding rivers, are receding rapidly and most of the land is arid and semi-arid. More than 40% of the population in this region is involved in agricultural production. Variability in the monsoon rains, massive floods and droughts further add to its vulnerability [
21,
22]. The cumulative effect of all these climate peculiarities puts the country in a severe threat of food, water and energy security [
23,
24,
25].
Empirical literature based on crop modeling in Pakistan reports that production of its major cereal crops is prone to high temperature and low rainfall [
26,
27,
28,
29]. Cropping seasons in Pakistan require a certain amount of heat and precipitation [
30]. Average temperature remains moderate during the wheat growing season. However; wheat does not receive enough rainfall to grow effectively. Most of the cultivated land is fed with irrigation water and post-monsoon rainfall. According to Pakistan economic survey 2016-17, 30% of the total cultivated area of the wheat crop is irrigated with canal water, while 55% is farmed through tube wells and other sources (
Appendix A). However, no water is available for the remaining 15%. The extent and spread of monsoon rain are declining over time, due to climate change. The summer monsoon comprises 60% of the total annual precipitation. Moreover, Pakistan has inadequate water storage facilities and aging water infrastructure, including its vast irrigation network, making it a water-stressed country [
31].
Despite the growing amount of literature on climate change-caused decline in crop yield in Pakistan, the nature and extent of its economic effects remain largely unstudied. Moreover, research on the consequences of these agricultural impacts for human livelihoods is quite limited. The majority of existing research focuses on partial equilibrium analysis of the direct effects of climate change variables, such as temperature and precipitation, on crop yields and output [
32,
33,
34,
35,
36,
37,
38,
39,
40,
41,
42]. These studies suggest reduced crop yield and production, due to climate change. However, partial equilibrium analysis has three broad limitations. First, these studies only emphasize crop output or revenue, and therefore, give an incomplete understanding of the implication of crop yield changes for human livelihood. Secondly, they overlook the importance of climate change with respect to income and expenditure of different types of households. Lastly, they overlook the inter-connections of different countries and their production systems that might influence the domestic price. Keeping in mind the interlinkages of domestic and global economies, the effects of changing climate on agricultural production would not just be limited to crop yield, but would affect the whole economy. Agricultural output is consumed directly and indirectly as raw materials. Any change in crop production would affect the overall economy. Hence, the results of existing partial analysis studies do not provide complete guidance to policy-makers.
2. Materials and Methods
The economic analysis of the impact of climate change on agricultural production of Pakistan begins by introducing a common set of climate change scenarios and crop yield inputs to be used as shocks in the global economic model. This integrated economic modelling framework of climate change links global climate models to an economic model through biophysical models. This research considers GCM MPI-ESM-MR global climate model of the latest Coupled Model Inter-comparison Project (CMIP5) family that combines a representative concentration pathway 8.5 (RCP 8.5), i.e., the most extreme emissions scenario. Moreover, the model considers socio-economic pathways (SSP2) in order to describe the future economic and population growth of the world. The climatic projections of the mid-21st century from the climate model are used [
43] to incorporate it into DSSAT and APSIM biophysical models. The mid-21st century climate change input in the crop models is used to simulate the impact of future climate on crop yield and production of the country. Within DSSAT, CERES-Wheat and CERES-Rice models (Crop Environment Resource Synthesis) are considered to predict the impact of future climate change on output of wheat and rice in Pakistan by 2050. The estimated decline of projected mean percentage in the output of wheat and rice from CERES-Wheat and CERES-Rice models under extreme emission scenarios is used in this research.
We use the output of these crop models in Global Economic Trade Model [
44] to analyze the economic effects of climate-induced loss of agricultural production by 2050. The economic model describes the response of producers and consumers to declines in crop output. As illustrated in
Figure 2, we combined global climate model, crop and economic models to examine the economic impact of climate change-induced loss of agricultural production in Pakistan.
MyGTAP model differentiates between a private household and government and provides the option to include multiple households and factors to explain comprehensive interlinkages within the economy. The graph shows the flow of all national and international economic transactions that take place within an economy.
2.1. Economic Analysis
The global computable general equilibrium model provides a framework for the economic analysis of the response of different producers and consumers to policy change. Global CGE model is supported by the newly-developed MyGTAP modeling framework [
44], and its global database provides data for the model. It is a multi-sector, multi-region modeling framework and is an extension of a standard GTAP model [
45]. In the standard GTAP model, there is only one representative household, which limits its ability to incorporate multiple households and evaluate the flow of income and expenditure within the economy. Instead, MyGTAP model differentiates between a private household and government and provides the option to include multiple households and factors to explain comprehensive interlinkages within the economy. The number of disaggregated households in the model enhances its ability to evaluate the impact of a policy change on the welfare of all households. Expenditure is divided into three categories, private expenditure, government expenditure and savings. All factors of production are owned by the regional household, which supplies their endowments to different firms. Firms use them to produce goods and supply further to households and government to satisfy their demand. Total saving consists of both private households and government saving which is further channelized for investment. New features introduced in the model are regional transfers, including remittances, foreign aid and foreign income. Income transfer between household and government is also incorporated in the model.
The GTAP database represents the world economy for three reference years; 2004, 2007 and 2011. The latest reference year, 2011, is used in this study. The database comprises 140 regions, 119 countries and 21 aggregated regions. The database also includes 57 sectors for every region. Keeping in mind the importance of the agriculture sector in Pakistan’s economy, and trade profile of this sector, the number of regions have been aggregated into 21 regions. Similarly, a number of sectors have been aggregated to 12 commodities, out of which six belong to the agriculture sector.
Since MyGTAP model differentiates private household and government in a separate account, it can be mapped with a Social Accounting Matrix (SAM). A SAM represents the flow of all national and international economic transactions that take place within an economy. The recently released Pakistan SAM 2011 is used in this study. It consists of income and expenditure flow of 16 types of households and 12 types of production factors. Household types are further differentiated as rural or urban. There are 12 types of rural households which are further divided based on land ownership, farm size and non-farm activity. This classification includes six types of farmers, two farmworkers, and four types are based on non-farming activity. The small and medium farmer owns less than and more than 12.5-acre agriculture land, respectively. The rest of the rural-based types are employed in farm work, but do not own land. The last four households are urban-based (
Appendix B).
The SAM contains 62 types of commodities where 16 types belong to the agriculture sector. It incorporates 87 different activities, including services. The share of each factor of production in the production of 87 activities has been mapped with the 12 aggregated sectors of GTAP. Similarly, household consumption of 62 types of commodities is mapped with GTAP sectoral aggregation of 57 commodities. Moreover, households’ income is linked with returns of factors of production as factor ownership shares. Twenty-one factors from SAM (
Appendix C) are mapped with five standard factors of production in MyGTAP model. SAM also enlists transfer of income between households and the government. Households pay taxes to the government, while they receive income in the form of government spending. The income transfer within SAM is mapped with MyGTAP single private household and government entity.
Figure 2 explains the economic integration of MyGTAP and SAM 2013.
One of the significant advantages of the Global CGE model is its ability to relate cross-linkages within the economy [
44]. The MyGTAP model has also been used to examine policies in Pakistan [
46,
47], Nepal [
48], Oman [
49] and Nigeria [
50] Based on neoclassical theory, the model assumes perfect competition in the market. Therefore, market adopts constant returns to scale, where producers’ decisions are based on profit maximization and cost minimization, while consumers strive to achieve utility maximization [
51]. It is a consistent model and can capture both economy-wide effects, as well as interaction and inter-linkages between different sectors of the economy.
2.2. Baseline
To analyze economic impacts of climate-based changes in agricultural production, a baseline representing the business as usual (BAU) scenario of the world economy in 2050 has been created by using projected data of macroeconomic variables, including GDP, population, and supplies of factors like labor and capital (
Table 1). Baseline represents an economy with no change in the climate. The MyGTAP database contains eight types of elements of production that are aggregated to five factors. This includes skilled labor, unskilled labor, capital, land, and natural resources. SAM 2013 holds 21 factors of production where three belong to farm labor, two from non-farm labor, three from land, one belongs to livestock and three are capital types. These factors are mapped with five standard elements of MyGTAP framework. The share of each labor and capital factor in total labor and capital supply is calculated and projected to the year 2050.
2.3. Simulation Design
The experiment on the updated database from baseline is carried out by incorporating adverse production shocks of wheat and paddy rice from the CERES-Wheat and CERES-Rice DSSAT biophysical models, respectively. Simulated shocks are based on DSSAT Bio-Physical Models in case of Pakistan [
43]. A comparison between baseline, i.e., without climate change, and the counter-experiment with climate change effects describe the economic impact of climate change-induced decline in wheat and rice production in Pakistan by 2050.
2.4. Model Closure (Assumptions)
The standard MyGTAP closures are taken as the starting point for our analysis. This assumes that there is perfect competition (zero economic profits) in all sectors. The production factors, capital and labor, are considered to be fully mobile between areas, whereas, land and natural resources factors are sluggish to move. Government spending is assumed to be a constant share of government income, and there is no tax replacement. Private households are assumed to allocate income across consumption, assuming a CDE utility function. Foreign income flows are assumed to rise or fall with factor prices in the country in which they are located. Investment is driven by the expected rate of return as in standard GTAP and total domestic savings by the sum of private household savings and the government budget deficit. Hence the trade balance is endogenous.
2.5. Mathematical Model
Income-expenditure: The income-expenditure flow of global accounts is presented in
Figure 2. The government collects income from taxes and foreign aid and consumes it in the form of government expenditure. The difference between income and expenditure could either be deficit or saving. It is expressed in the equation, where GOVINC is government income, AIDI and AIDO is the foreign aid in and out of the country, HHLD TRNG is the transfers from government to households in the form of public expenditure. In MYGTAP model, coefficients are capitalized, while variables are represented in lower case letters [
44].
Similar to the government account, private household collects income factors of production, remittances, and government. Each household supplies endowments to firms and the total supply of each grant are the sum of grants supplied by all households [
44]. The ownership of capital is also included in the total household income, and therefore, an appropriate amount of depreciation is reduced from the income. It is expressed in an equation, where EVOAH is the income received from factors of production less depreciation (VDEPH), plus net foreign labor remittances (REMIH and REMOH) and foreign capital income (FYIH and FYOH), transfers between households (TRNH) and from the government (TRNG). The subscript ’
i’ represents the factor type, ‘
h’ is the household type, while ‘
r’ represents the region in the model [
44].
Gross Domestic Product: GDP from the expenditure side is calculated by adding regional consumption, investment, exports at world prices, and subtracting imports at market prices. However, from the source side, it is a summation of net factors income (NETFACTINC), net taxes (NETAXES), and capital depreciation (VDEP) [
44].
Exports and Imports: The decomposition of exports at world price includes the value of exports at market price plus the export tax. Similarly, the decomposition of imports at market price includes the value of imports at the world price plus import taxes [
44].
Within microeconomic variables, domestic sectoral production, private domestic consumption, and the sectoral price at both supply and demand are the chosen variables. Private consumption is based on Armington elasticities. First ESUBD_R, the standard GTAP region-generic elasticity is defined and read into the model from the GTAP Database. Next, a region-specific elasticity is defined. This is initially set equal to the region-generic unless an additional header exists, “ESDR” containing region-specific details [
44]. The formula for the industry output is given in Equation (7). Here ‘
qo’ represents the output of industry ‘
i’ in region ‘
r’. It is equal to the sectoral share and output of each household as
SHREVOMH(I,h,r) and
qoh(i,h,r).
Equation (8) provides the formula to calculate supply price, where
is a share of each household in total sectoral production in region
r and
psh is supply price for each household.
Sectoral Export Share in total Output: Equation (9) provides the formula to calculate the export share. Here
is the total exports of the country, while
is total production. Moreover, the subscript i represents the sector, while r is the region
Sectoral Import Share in total Consumption: The formula to calculate the import share is given in Equation (10). Here
represents the domestic consumption of imported goods, and
is the domestic consumption of domestic goods.
2.6. Database and Aggregations
This research has gathered and analyzed data from seven different databases. The two major datasets used in this study are the latest available GTAP database [
52] and Pakistan’s Social Accounting Matrix (SAM) for the year 2011 constructed by International Food Policy Research Institute (IFPRI) under the Pakistan Strategy support program. The Pakistan’s SAM 2011 is incorporated in the MyGTAP modelling framework to augment required data. To develop constant climate baseline values, we use projected growth rates from the base year, 2011, through to 2050, for GDP, population, factor supplies, and food production to feed the projected population. Projected data for GDP and population is acquired from the IMF World Economic Outlook 2017 database and CEPII database. These data are then cross-checked from socioeconomic pathways (SSP2) projected data of moderate economic and population growth. Projected data for capital and skilled and unskilled labor is gathered from ImpactEcon (
www.impactecon.com).
4. Conclusions
This research has explored both macro and micro-level economic effects of climate change on Pakistan’s wheat and rice crops by employing a country-specific computable general equilibrium (CGE) model of the Pakistani Economy. The research provides evidence of the negative effects of climate change-induced loss of crop production on the overall Pakistani economy by 2050. Since agriculture is one of the dominant sectors of the economy, real GDP will decline significantly. A decline in crop production, due to climate change not only affects the agricultural sector, but its results could extend to all agriculture-related industries and beyond, such as manufacturing and services. The change in crop production will have a multiplier effect.
By using an integrated model with a global and national database of GTAP and SAM, respectively, this study concludes that climate change will have some serious implications at the household level. Climate-led changes in crop production will have consequences on the returns of factors of production, incomes and consumption of different types of households. A huge rise in commodity prices will create a great challenge for the livelihood of the whole country, especially for urban households. The domestic price of wheat and rice will go up by as much as 17 and 31 percent, respectively. Hence, upward pressure on food prices will cause food security problems in the country. If the adaptation to climate change is ineffective, the resulting massive increase in commodity prices will pose significant challenges for the country’s livelihoods.
The research draws some severe policy implications of broader perspective related to climate change. The government needs to undergo long-term strategies related to climate variability to support small and medium farmers and farm workers. Considering the likelihood of future climatic disasters, especially flash floods, the country needs to invest in irrigated and non-irrigated water management technologies. The government should provide farm advisory services, and weather forecasting and marketing information to the agriculture growers. It is suggested that the government have a sound agricultural policy that can play a role in influencing its ability to adapt successfully to climate change as adaptation is necessary for high production and net returns of the agricultural output [
54,
55,
56].
5. Limitations
Like any other economic research, this study is not free of limitations. It focuses only on the economic component of assessment by investigating the future endogenous response of an economic model of agriculture to the different climate change scenarios by 2050. It does not explore the biophysical aspects of climate change impacts in detail, including those determining the actual cost of damage to crop production and yield. Therefore, a crop modelling study, along with economic modelling, is required to evaluate the actual climatic factors responsible for the loss of crop yield and output.
Furthermore, a numerical assessment of the impacts and possible adaptation to climate change would require a much-expanded modelling framework. Despite the above limitations, our results provide evidence that serious policy planning and implementation of adaptation strategies are required in the near future to help reduce the negative impact of climate change on the agricultural sector.