1. Introduction
The effects of global climate change, such as varying rainfall intensity, duration, and frequency; extreme weather; increasing temperatures; significant variations in solar radiation; increasing greenhouse gaseous emissions, can have an impact on agricultural, forest, and other natural resources, including water sourced from climate-sensitive water reservoirs [
1,
2,
3,
4]. In the agricultural sector, climate change will affect crop growth and yields as well as production due to an increasing number of drought and flood events, which will indirectly affect economic stability, although the impact will vary with region and crop type [
5,
6,
7]. Moreover, developing countries will suffer more than developed countries due to agricultural production strategies driven by economic plans under climate change scenarios. According to reports, the global temperature will increase by 2–3 °C in 2030–2050 [
8], and temperature increases of up to 2 °C or higher are expected to reduce the yields of global prime crops, such as rice, maize, and wheat [
9]. Furthermore, climate change has led to substantial changes in the dates of planting and harvesting, which has led to changes in the growing season due to variations and uncertainties in rainfall and temperature, thereby impacting food demand [
10,
11].
Rice, which is the staple food for most people around the world, is produced at approximately 480 MMT annually [
12], and is consumed by approximately 557 million people in Asia. It serves as a cornerstone of cultural, social, and economic development [
9,
12]. However, meeting the food demands of an ever-increasing human population remains challenging [
13]. A 10–100% increase in crop production is required for sustaining the global population by 2050 [
14]. Moreover, an annual conversion of 2.7–4.9 million hectares (ha) of land to cropland is required to meet the future estimated food production [
15]. Indonesia’s population and rice consumption are projected to increase by approximately 31% (2015: 257 million; 2050: 322 million) and 45% [
16], respectively, resulting in potential food shortages and affecting food security [
17]. Conversely, several factors affect rice production, including management practices such as tillage operations, cultivar type, sowing density, transplantation date, plant density, fertilizer management, chemical application, and water management. Furthermore, environmental factors, such as temperature, precipitation, solar radiation, wind speed, and humidity, directly impact crop growth and yield [
18]. Moreover, the climate in Indonesia is predicted to become hotter and more seasonal, with delayed onset of the summer monsoon and reduced rice production by approximately 14% [
19] that could further impair food security. Climate change could also cause losses of 12,446 ha of agricultural area and 885,430 t of rice production [
20], whereby rice paddy fields recently suffering from drought reached 25,580 to 867,930 ha per year and damaged 4614 to 192,331 ha of land [
21].
Climate change will aggravate rice production under climatic variability [
22]. Rice growth is sensitive to temperature, where warm daytime temperatures provide ideal conditions, and extreme heat events over 35 °C for even a few hours can impair plant physiology and deteriorate rice quantity and quality [
8]. Rice requires substantially more water than other grain crops, namely 450–700 mm during its growing season or 1.9–2.25 mm/day [
23]. Rice grows poorly if water-stressed, particularly during the transplanting and reproductive stages [
24]. In Indonesia, most rice is grown during the rainy season under rainfed conditions with minimal irrigation where precipitation level and timing are critical. These factors will be more vulnerable under climate change since rainfall will also have significant temporal and spatial variations that affect rice management strategies.
Mitigating potential food security issues by projecting future rice production in Indonesia through a climate and crop simulation model is crucial to anticipate the impact of climate change on rice production. Recently, DSSAT-CERES-Rice with a combined climate model has been widely used to assess the impacts of climate change on future rice production [
25,
26,
27]. In the present study, a combination of top-down and bottom-up approaches adopted from a previous study [
26] is proposed by evaluating and predicting the effect of climate change on rice production using a climate and crop model. Climate models will predict the climate in the future, and crop models will simulate crop growth and yield using other predicted future climate input data such as soil properties data, management practices, and agronomic characteristics. This study aimed to evaluate climate change scenarios that impact rice production through several climate change scenarios using a combination of the MarkSim daily weather generator and DSSAT-CERES-Rice for predicting future rice production with different (representative concentration pathways (RCP) 2.6, RCP 4.5, RCP 6.0, and RCP 8.5) scenarios on rice production in Indonesia for the 2021–2050 period. Farmers, researchers, and policymakers can utilize the results of this research to determine optimal rice production management practices for anticipating and adapting to future climate change.
4. Discussion
The global food demand is rising with increasing global population to levels where the food demand will double by the end of 2050 [
41]. Therefore, global agriculture will need to increase rice production, either by increasing the agricultural land area for rice cultivation or by enhancing productivity on existing agricultural lands using appropriate management practices. However, increasing agricultural production will encounter climate change barriers, which directly affect agricultural production by increasing temperature and altering rainfall intensity and frequency. These scenarios can reduce food production by decreasing land production or from crop failure due to drought and flood. Therefore, forecasting future crop production to avoid crop failure by designing and implementing climate change adaptation strategies is crucial for ensuring food security. In this study, we combined the MarkSim daily weather generator with an ensemble output from 17 GCMs and the DSSAT-CERES-Rice model to predict future rice production under different climate change scenarios and determine the probability of adaptive strategies based on climate and crop model results.
The uncertainty of the climate model to produce realistic results can be attributed to the scenario, model, time period, and their predicted number of generations [
42]. Several studies have analyzed the uncertainty of climate change on rice production [
25,
26,
43,
44,
45,
46,
47,
48]. These studies indicated that uncertainty is a major issue for the adaptation of policies and strategies to reduce the impacts of climate change on rice production [
25,
26,
43,
44,
45,
46,
47,
48]. Uncertainty may arise from various sources, including parameter uncertainty and model uncertainty [
46], such as consideration of soil fertility and nutrient uptake in crop models and various SSP-RCP scenarios in climate projections. In this study, because temperature increases were associated with uncertainty in the impact of rainfall on rice production [
26], ensemble models with RCP/emission scenarios were employed to eliminate uncertainties associated with climate change projections [
43,
44]. The ensemble models provide the overall impacts of climate changes in terms of change in rice yields [
47]. Moreover, our study generates large projections using 17 GCM models because a large number of GCM projections can be considered a way to overcome certain levels of model uncertainty [
49,
50]. In our study, the MarkSim results showed that temperatures would increase by 2 °C at the end of the 2050s, as seen in a recent study [
51,
52]. Increases in the minimum and maximum temperatures have several impacts on rice yield [
44]. A large difference between T
max and T
min in the study area can lead to vulnerability in rice growth and development; thus, water management is required to prevent crop failure; for example, irrigation water supply may increase rainfed rice yields during the flowering stage [
26]. Projected rainfall patterns showed more significant temporal and spatial variation and will decrease gradually by the end of the 2050s. Previous studies reported that future rainfall might increase and decrease in several regions in Indonesia [
53], implying that rainfall differs depending on multiple factors, including topography, location, surface sea temperature, and latitude. Similarly, a previous study evaluated the effects of climate change on rainfed rice production in the Songkhram River Basin, Thailand, using the DSSAT-CERES-Rice model, where scenarios under RCP 8.5 showed the largest reduction in rice production [
25,
26]. Generally, our results suggest that climate change alter in rainfall patterns, temperature increases, and average solar radiation, all of which contribute to reducing rice production across all three growing seasons under different climate scenarios. The results of our study support other relevant studies showing that increasing temperature and changing rainfall frequency and intensity reduce rice production [
17]. Moreover, our results corroborate those of previous studies indicating that RCP 8.5 will lead to the largest reduction in rice production.
Natural or social events may also lead to uncertainty in rice production. In this study, there was a significant gap in rice production over the years due to El Nino and La Nina events, which contributed to decreasing rice production due to a lack of water and flooding, significantly influencing crops growth. This is consistent with the findings of previous studies that indicated El Nino and La Nina have negative impacts on rainfall intensity, frequency, and duration as well as rice production, particularly in rainfed ecosystems that are more vulnerable to El Nino [
54,
55]. El Nino and La Nina are natural events that increase or decrease ocean temperatures, affecting rainfall intensity. El Nino delayed rainfall (leading to less rainfall), whereas La Nina led to higher rainfall. These events increased the variation of the rice production in the baseline period.
The future rice production was assessed based on the ensemble output and the value of rice genetics parameters calibrated and validated through GenCalc software. High rainfall may reduce rice production due to moisture stress [
56], severely damaging or even killing rice plants in areas receiving water from precipitation up to 100 mm, according to future rice yield simulations. Further, rainfall frequency affects solar radiation, which is essential for rice growth, especially during the generative stage. Conversely, appropriate drainage management during the wet season is key to reducing moisture stress and avoiding flood events since rainfall intensity is most concentrated in this season [
53]. During the first dry season, the decrease in rice production is lower than that during the wet season because during the first dry season, the total rainfall falls within the required water supply range for rice growth. Moreover, the first dry season has the highest number of days without increasing rainfall, although total annual rainfall shows an increasing trend. Increasing the maximum and minimum temperatures may reduce the rice production because they gradually increase during the first dry season until the end of 2050. Overall, the highest reduction in rice production will occur during the second dry season, which supports the results of previous studies [
57]. As mentioned above, increasing annual maximum and minimum temperature will be greatest during the second dry season, which directly influences not only growth duration but also growth pattern and rice crop productivity from extreme temperatures (low or high), harming the rice plant. Conversely, solar radiation is an essential driver for biomass production, accumulation, and distribution, but increasing radiation, as well as elevated CO
2 concentration, contribute to global climate change [
58]. Most crop failure occurs when the plant encounters water stress due to water scarcity and high temperature, especially at the end of the vegetative stage and reproductive stages. Therefore, water availability is a key factor in rice growth, and less water during the early vegetative stage will substantially impact rice growth [
59]. Our study showed that the Ciherang variety would face similar problems under climate change scenarios. Thus, policymakers should consider a policy that emphasizes climate adaptation strategies at the farm level to prevent rice shortages, such as irrigation water supply planning during the rice-flowering stage [
26]. Moreover, shifting of the rice planting date was studied as an adaptation strategy to reduce the impact of climate change on rice production [
60]. Shifting the fertilizer application date was also proposed for rice production under various climate change scenarios [
26].
Because climate will be more seasonal and temporal in the future, we have recommended several policies and adaptation strategies that can be encouraged at a farm-scale level in the areas identified in
Table 4.
The policies and adaptation strategies to rice production at the farm level help offset negative impacts of climate change and are easily implemented, including shifting planting and transplanting dates, changing the sowing density [
61], irrigation management, developing new agricultural areas and using heat-resistant crop varieties [
62,
63], changing fertilizer application dates, and the dose [
26], and reducing tillage and organic amendments [
64]. Appropriate adaptation strategies typically differ from one location to another due to regional climate effects, which need to be reviewed [
65,
66]. Current rice transplanting dates are around the third week of November to the first week of December (wet season), the third week of March to the first week of April (first dry season), and the third week of July to the first week of August (second dry season) [
67]. We propose shifting the planting date earlier in the year for all three growing seasons (the fourth week of October to the first week of November for the wet season, the fourth week of February to the first week of March for the first dry season, and the fourth week of June to the first week of July for second dry season), which will coincide with the start of the rainy season in early October. The patterns of future rainfall are predicted to begin earlier; forwarding the planting date will help prevent flooding during the wet season and potential water deficits in the dry season. Therefore, shifting the planting date is important for avoiding crop failure under spatially and temporally variable rainfall patterns. Moreover, implementing appropriate fertilizer management practices, such as improving application frequency and dosage, the number of split doses, number of fertilizers applied per split, and color charts for increasing rice yield per unit area, has become an important factor in increasing rice production [
68]. For instance, using N fertilizer that fails to appropriately balance P and K levels negatively affects rice yield, soil quality, and the surrounding environment, as well as increasing the incidence of crop lodging, weed competition, and pest attacks [
68,
69]. Implementing plant nutrient management (IPNM) [
70] may help increase nutrient efficiency in these areas by judiciously manipulating nutrient distribution to preserve and enhance soil fecundity for long-term, sustainable rice productivity [
71]. Examples include using fertilizer nutrients as a supplement for nutrients supplied by different organic sources available at farms. Saptutyningsih et al. (2020) reported that farmers with high social capital were willing to adopt adaptation procedures in Indonesia [
72]. In addition, educating farmers to adopt adaptation strategies [
73] will help bridge the climate change knowledge gap between farmers and researchers [
74]. Furthermore, to achieve sustainable agriculture in this area, several strategies can be applied, such as reforestation [
75], soil and water conservation practices [
76], agroforestry [
77], permaculture [
78], and crop rotation [
79], which can contribute to environmental conservation for better ecosystems and diversity, and the existence of natural resources as life support. Additionally, the development of crop weather insurance is important to protect farmers’ economies. Finally, the dynamic cropping calendar, modernization of irrigation systems, and integrated plant nutrient management plan based on the above adaptation strategies under various climate change scenarios will be helpful for the adaptation of the negative impacts of climate change on rice production.