Climate change impacts on global potato yields: a review

Potatoes as a food crop contribute to zero hunger: Sustainable Development Goal 2. Over the years, the global potato supply has increased by more than double consumption. Changing climatic conditions are a significant determinant of crop growth and development due to the impacts of meteorological conditions, such as temperature, precipitation, and solar radiation, on yields, placing nations under the threat of food insecurity. Potatoes are prone to climatic variables such as heat, precipitation, atmospheric carbon dioxide (CO2), droughts, and unexpected frosts. A crop simulation model (CSM) is useful for assessing the effects of climate and various cultivation environments on potato growth and yields. This article aims to review recent literature on known and potential effects of climate change on global potato yields and further highlights tools and methods for assessing those effects. In particular, this review will explore (1) global potato production, growth and varieties; (2) a review of the mechanisms by which changing climates impact potato yields; (3) a review of CSMs as tools for assessing the impacts of climate change on potato yields, and (4) most importantly, this review identifies critical gaps in data availability, modeling tools, and adaptation measures, that lays a foundation for future research toward sustainable potato production under the changing climate.


Introduction
In the pursuit of achieving zero hunger (SDG 2-Sustainable Development Goal 2), tackling climate change (SDG 13-climate action) is crucial [1][2][3] to enhance food security, which ascertains timely economic, physical, and social access to nutritious, sufficient, and safe food for proper dietary and healthy living [4,5].In this regard, providing quality and stable food with sufficient access is essential to end hunger, malnutrition, and food insecurity, considering the four pillars of food security (availability, access, stability, and utilization).In addition to investing in the food system (funding farmers and providing agriculture equipment), ensuring food's nutritional standards and affordability is equally essential.In this context, potatoes are a significant stable crop that is thought to be nutrient-dense, affordable, widely accessible, and could significantly contribute to ending hunger to maintain food security [5][6][7][8].
Potatoes are essential crops that contribute to food security in the current food system because of their many values [4].Regarding food nutrition, supply, and security, with global climate change challenges significantly resulting from current population growth, potatoes are recommended as a staple crop for human consumption [4,9].Potatoes are plant-based protein, a nutrient-dense vegetable crop that can be used to substitute animal-based protein.International development organizations have begun to appreciate the smallholder expertise that allowed potatoes to preserve their genetic diversity [10].Potatoes withstand inclement weather more than most major crops [11,12].Potato farming generates revenue and jobs [4]; the contemporary history of potatoes enumerates that potatoes play a crucial role in national security [10].Many countries have registered specific potato varieties as part of their national patrimony.Potatoes production has a lower carbon footprint, and their cultivation requires less water supply than many other crops [4,12].Notably, according to some studies, potatoes' high glycemic index raises the risk of obesity.On the contrary, recent clinical intervention and observational studies reviews concluded that convincing evidence is not available to link potato intake to risks of obesity, cardiovascular disease or Type II diabetes [4].
This paper focuses on climate variables (precipitation, temperature, and atmospheric CO 2 concentration) and simulates their impacts on potato yield, which is vital.However, farm management practices determine two-thirds of potato yield variation [2], while extreme weather significantly impacts its yields [6].Researchers have employed crop simulation models (CSMs) in simulating the impacts of climate change on potato yields caused chiefly by increased greenhouse gases (GHGs) and various management options for sustained potato production.The effectiveness of the models has brought about a series of programs able to model crop growth, development, and production using genotype, environmental, and management information.This review explores the recent and past literature on the impacts of climate change on potato yields.Additionally, it identifies the research gaps that must be filled to assess the impacts of changing climatic conditions.This literature identifies the effects of the changing environment as a global challenge to food and nutritional security.The atmospheric GHG emissions increase temperature.Many studies have assessed the impacts of the changing climatic conditions on agriculture using different techniques, some suggesting CSMs with climate scenarios to predict the effects of climatic changes on crops and examine various adaptation strategies for optimal production.
According to the literature, climate variables determine potatoes' growth and yields [16][17][18][19][20]. Adesina and Thomas [16] modeled the potential effects of climatic changes on the United Kingdom's potato production and reported that future climate scenarios hinder land preparation and harvest operations in the Northern regions.At the same time, some parts are prone to irrigation and water demand, and drought increases as evapotranspiration increases and potato irrigation is predicted to double.Bender & and Sentelhas [17] simulated the impacts of projected climate change for varying growing seasons on potatoes in the producing regions of central Brazil.Their studies indicate that Brazil's climate would impact potato crops differently, determined by the planting season and production region.In their research, Holden et al [18] revealed that in Ireland, there would be extreme seasonal rainfall and an increase of about 1.6 • C in relative temperature, which could cause potato yields to decline in 2055 and 2075 for non-irrigated tubers.These findings inform that the irrigation demand for potato growth will be significant and most likely make the crop non-viable for farmers, especially in the eastern region of Ireland, where competition for water exists in summer.Li and Zhang [20] simulated the impacts of changing climate on China's northwest region potato yields.Their study shows that potato yields increased from 1982 to 2015, distinctively with planting area and an inter-annual variation.There is a significant increase in temperature compared to most other climatic factors during the potato development in China's northeast region.Naz et al [19] modeled the impact of climate warming on potato phenology in Pakistan from 1980 to 2018.They discovered that the predicted phenology stages occurred earlier with increased temperature, and the impacts on the phenological steps observed were insignificant.This article's focus is on climate change globally impacting potato yields.As a review, it synthesizes relevant literature that assesses the impacts of changing climate on potato yields.First, it overviews vital themes pertinent to global potato yields, including growth stages, varieties, and production.Second, we narrow the discussion to the impacts of climatic changes as a threat to food security, pointing to the effects of various climatic variables on potato yields and, as an adaptation strategy, enumerating the different methods of assessing the climate change impacts on potato yields.Third, the article describes CSMs as a tool for evaluating the climate change impacts on potato yields to inform adaptation methods and briefly highlights an example of CSM, the Decision Support System for Agrotechnology Transfer (DSSAT).Finally, this paper addresses research gaps and directions for future research.
Information and data were sourced from published articles, reports, and databases.We used various keywords and database sources to search for literature and relevant studies; keyword combinations from the first category (climate change impacts, potato yields, DSSAT, future scenario) and the second category (CSM, management practices, food security).A total of 235 papers and articles were gathered through a literature search; the most relevant were cited and referenced in this review paper.The data sources present the regions/countries, prospective year, cultivar, model, scenario, yield, and references (supplementary information S1).

Growth stages, varieties, and global production of potatoes
Potatoes, a member of the family Solanaceae, known as Solanum tuberosum L., originated in the Andean Mountains region of South America [21,22].In Andean, it is a crop consumed as food and domesticated pre-Columbian for over 10 000 and 8000 years, respectively [23].

Overview and growth stages of potatoes
Potatoes are an essential food crop that provides a tremendous edible protein and a high, dry matter required for human consumption; a tuber approximately composed of 2.1% protein, 70%-80% water, 1.1% crude fiber, 20.6% carbohydrate, 0.3% fat, and 0.9% ash [24].Potatoes, the fourth most common and essential food crop eaten globally, after rice, wheat, and maize [25], have excellent yield production and high nutritional value [22,25].Potatoes are grown using tubers (seed tubers), through which main stems originate and consist of a variable number of primary branches.They exhibit varying branching depending on the genotype, the tuber's physiological age and the conditions of the environment [21].Potato plants require varying nutrient levels at different growth phases.Potatoes have five most vital developmental steps that determine the yields: the development of sprouts, vegetative development, initiation of tuber, bulking of tuber, and maturity [26][27][28][29][30].

Potato varieties
About five thousand potato varieties exist worldwide, and nearly three thousand are from the Andes alone, majorly in Chile, Ecuador, Peru, Colombia, and Bolivia.The two major subspecies of potatoes (S. tuberosum L.) are andigena (Andean) and tuberosum (Chilean) [22].Different criteria are used to classify varieties of potatoes; a standard of classification is the number of days it takes potatoes to mature from the planting day.For instance, varieties with maturity days of 65-70 are classified as very early, 70-90 d as early, 90-100 d as mid-season, 110-130 d as late, and more than 130 d as very late.Regardless of the maturity days, potato varieties tend to produce higher or lower yields; those with short maturity days are often harvested early as small, succulent potatoes and are often called 'new potatoes,' which are usually boiled for table use [22,23].Potato varieties can also be classified according to the quality traits suited to a particular processing or cooking method, such as frying, baking, boiling, or dehydrating [31][32][33][34][35].The preferred cultivars for frying are separated into French fry (elongate) or chipping (round) types (figure 2) [36].However, the popularity of potato varieties differs by geographical region, and while some are common varieties globally, others are specific to certain areas [22,23].Varieties may be classified based on storage qualities.Some cultivars must be consumed or processed immediately after harvest, while others maintain their starch contents longer in storage [23].

Global production of potatoes
According to FAO (2019), potato production has grown globally by roughly 20% since 1990, but it is still below the individual production of wheat, maize, and rice [37].High yields per unit area are a factor that made potatoes achieve global popularity compared to other food crops.The Food and Agriculture Organization of the United Nations (FAO) presents the global potato production in million tonnes/mega tonnes (Mt) (figure 3) from 2005 to 2021 [38].
It has been suggested that growing potatoes will ensure future food security because of their remarkably high adaptive capacity and short life span, giving efficient yields per cultivation [4,25,[39][40][41][42][43]. Figure 4 presents the percentage distribution of global potato production by continent in 2018.It can be seen that Asia and Europe together can contribute to about 80% of global potato production [38].
Many growing areas expect an increase in potato yields, and North American parts achieve a high production level because of many factors.For instance, scale efficiencies, mechanization, high inputs (fertilizer, pesticides), a cool climate with ample rainfall, and a long cultivation season favor the long-season  cultivars with high yields.Also, a system of production that rotates with forages and cereals improves soil quality and eliminates disease [23].The chart outlines the potato yields by country in 2020 [44] and potato consumption per capita by Helgi Library [45] (figure 5).In terms of potato production, China is in the lead, followed by India, Russia, Ukraine, and the United States of America [44].

China
China is responsible for about 20% of the world's potato production [20,43,[46][47][48][49].The quantity of potatoes produced per hectare in China increases as cultivated land increases.The northern and southwest regions produce the highest quantity of potatoes [47][48][49].The acreage of potatoes in China is high, 49% in Northern China, where single cropping exists.In Southwestern China, 39% of single and double cropping mixes exist.Double cropping exists primarily in central China with 5%.7% of the potatoes are in Guangxi, Taiwan, Hainan, Fujian, and Guangdong in Southern China [43,49].

India
In India, potatoes are the fourth food crop after maize, wheat, and rice.India is the second-highest producer of potatoes [24,25,[50][51][52][53][54][55].In 2016, the land used to cultivate potatoes amounted to 2.13 million hectares (Mha), yielding almost 44 Mt dry weight annually [56,57].The planting period varies from area to area in India; for instance, in January-February, the spring crop is planted in the hills of Uttar Pradesh and Himachal Pradesh.In contrast, the summer crop is grown in May.In January, the spring crop is grown in Bihar, Haryana, West Bengal, Punjab, and Uttar Pradesh, but the main crop is grown in October.At the end of June, the Kharif crop is repressed in Karnataka, Maharashtra, and Madhya Pradesh, whereas the Rabi crop is planted mid-October-November [58].

Russia
Russia is among the highest potato-producing countries [59,60].FAOSTAT reported the production of potatoes in the Russian Federation to be 30 Mt (8.2% of worldwide production) in 2013, and the harvested area was 2.1 Mha (10.7%).The import of potatoes by Russia is rather small, with annual production that does not exceed about 0.6 Mt between 2000 and 2010.After the extreme drought that reduced Russia's potato production in 2010, the highest imported potato was 1.4 Mt in 2011.Larger agricultural enterprises in Russia since the 2000s have been increasing potato yields [59,60].

Ukraine
Ukraine is among the top five potato-producing countries globally, has almost half of the country's 1.5 Mha of potato farms with black soils of the forest-steppe zone located in central Ukraine, although the Polesye wetlands of the north harvest the best yields [61][62][63].Annually, the country harvests approximately 20 Mt, like the USA, and most are grown on a small scale for domestic consumption.Commercial production land is only about 55 000 ha.In Ukraine, the structure of using the produced potatoes is entirely different; 26%-32% is used for food, 29%-33% for livestock feed, and up to 10% for gross production of non-food items [61].In 2004, production attained a record of 20.7 Mt, with a yield average of about 13 t ha −1 [63].

United States
According to Alva et al [64], the US is ranked fifth among the most prominent countries producing potatoes globally.In 2007, the US harvested 19.9 Mt of potatoes, ranking the fifth-highest producer globally.In the US, potatoes are harvested in the ninth and tenth month of the year [65].Potato yields in the region range from 27 to 36 t ha −1 [64].On a large scale, potatoes are rotated with other crops, such as wheat, maize, and vegetables, for ideal growing conditions [66].In the US, only about one-third of the potatoes are eaten fresh [65], and growing regions flaunt fertile, rich soil and an ideal climate appropriate for planting potatoes [67].
Countries have varying attributes and methods of cultivating and processing potatoes, such as varieties, planting seasons, harvesting, and uses.Meanwhile, climatic variables have a significant impact on potato production.

Climate change and potato yields
The effects of the changing climate on potatoes appear to be complicated, but different studies have used varying methods for the evaluation.Elevated temperatures can result in low yields because of increased development rates and higher respiration, depending on the temperature.Increased atmospheric carbon dioxide (CO 2 ) resulting in global warming will likely improve potato yields [68].Moreover, CO 2 is reported to alter the nutritional content of potato tubers.Increased CO 2 concentrations increase soluble starch and sugar and reduce the tuber's protein and zinc concentration [69,70].

Climate change
The global climate is changing and is presently a big challenge that has attracted substantial attention [20,71,72].GHG is an anthropogenic emission causing significant planet-warming [73], influencing the world's climate, and leading to climate change [74,75]  Climate data sources are available, and they include private or government organizations [72,76].Models generate predictions using soil, meteorological and crop data in numerical simulations.The Global Climate Model (GCM), also known as the General Circulation Model, is a tool presently accessible to simulate the global climate process that results from GHGs.The GCMs focus on changes in temperature and precipitation and can be categorized into three, namely: Atmospheric-GCM (AGCM), Oceanic-GCM (OGCM), and Atmospheric Oceanic-GCM (AOGCM) [77].Figure 6 shows the atmospheric CO 2 concentrations and temperature under the Shared Socioeconomic Pathways (SSPs) [78,79].
The susceptibility of climate is threatening the global climatic cycles and, as a result, threatening the world food production systems, invariably affecting livelihood [80].Climate change is a global phenomenon impacting crop plants negatively, affecting access to food crops.

Climate change and food security
The objectives of enhancing and sustaining global food security in the agricultural sector are determined significantly by climatic conditions.The agriculture sector is experiencing increased requirements, competitive natural resources, and impacts of biotic (e.g.pests and diseases damages) and abiotic (e.g.precipitation and temperature changes and intense weather variation) factors.The effects of enormous temporal and geographic unpredictability and flexibility confound the challenge [81].Agriculture is susceptible to climatic and environmental situations.Globally, an average surface temperature increase from 1.4 • C to 5.8 • C is possible towards 2100, and there is an expectation that this warming will significantly influence the availability of water and precipitation patterns.An increase in the variability may accompany the precipitation changes and directly affect plant growth, development, and crop yields, along with the estimated increase in the concentration of atmospheric CO 2 .Climatic condition changes initiated by GHGs would cause a notable change in crop cultivation that could considerably impact socio-economic conditions [82].The balance between sources and sinks of GHG is vital to reducing climate change-related risks [80].
In 2007, the World Bank established five crucial features in which the changing climate will impact agricultural production: precipitation changes, temperature, level of atmospheric CO 2 , environment variation, and runoff surface water [83].Temperature, as well as rainfall, has a direct effect on potato production-furthermore, the rainfall co-influenced the soil moisture and freshwater levels as an essential input for crop development.Still, excessive rain causes flooding, which affects the crops negatively.The soil's temperature and moisture content determine the growing season's length and control the crop's development and water requirements [84].Yields tend to be reduced by warming beyond a precise temperature range to produce minimal yields.Likewise, the temperature increase obstructs the plant's capacity to access moisture easily.An increase in temperature evaporates the soil and increases leaf transpiration (evapotranspiration). Evapotranspiration competes with precipitation because of increased temperature impact on water availability, and evapotranspiration dominates.Carbon emissions, responsible for the change in climatic conditions, may benefit agriculture by enhancing photosynthesis; however, the science of agriculture benefitting from carbon fertilization is uncertain [83].Adaptation strategies are essential to climate change studies, i.e. options employed to respond to the impacts of the changing climate and vulnerability valuation.
Studies show that changing climatic conditions generally disrupt agricultural produce cultivation and economies [85].

Climate change impacts on potato yields
In the production of potatoes, climate change plays a vital role in determining the yields of harvested potatoes [68,86].Potatoes can adapt to some climate variables, such as drought, but are prone to some, such as high humidity and temperature changes.The cultivation of potatoes and the yields rely on a location and develop best in a remarkable, frost-free period but do not thrive with increased heat [68].Numerous experiments and observations quantitatively explained the yields of potatoes as a variable that depends on the condition of the climate (e.g.temperature, solar radiation, and length of a day).High yields come under extended photoperiods, and average temperatures produce high yields; meanwhile, the yields can be reduced by an increased temperature at the development stage of the potato tuber [55].

Temperature
Potato growth and yields will be negatively impacted by temperatures above 30 • C. It includes physical tuber damage, such as brownish patches, less starch breaking up in the tubers, and shortened or non-existent tuber dormancy, which causes tubers to sprout too early.Unlike in hot weather, potatoes are temperate crops and prefer to grow at temperatures below 25 • C [13,94,105].They can function between 25 • C and 30 • C, but it is not a suitable temperature.When the temperature is between 16 • C and 19 • C in the development stage, the plant will thrive if it fulfills the water requirements [86,88].The plant development halts when the temperature exceeds 30 • C and closes the stomata for moisture conservation.Many previous studies consider temperature more, compared to other variables, showing that high temperature impacts potato crops negatively [17,18,37,86,87,89,100,[102][103][104][106][107][108].

Drought
Potato crops thrive more in cool weather and are susceptible to water stress much more than many other crops.The two main reasons are soil types determining how well potatoes grow and a shallow root structure with most root parts at the top twelve inches of the soil.They grow well in soil with a low to medium capacity to hold water.Maintaining a standard soil moisture level throughout the potato growing season gives high-quality potatoes optimal yields.Regular irrigation is required with irregular rainfall because when the water table drops beyond 60%-65%, the soil moisture becomes critical [95,101].Areas presently experiencing excess rainfall might experience a long period of drought in the future [13].The Potato development duration, timing, and intensity of water scarcity determine drought effects on potato plants.Water deficiency reduces the growth rate while the potato grows, impacting the quality and yield [95]. Water requirement, e.g.precipitation, is the second standard variable considered in the study of the climatic change impacts on potatoes, and the effects vary by region [17,18,87,89,100,102,104,[106][107][108][109].

Precipitation
Potatoes need between 400 and 800 mm of water to thrive, depending on weather conditions and management practices.Potato growth and development, yields, and quality will be adversely affected by the shortage of water [13,109].Nevertheless, excessive water from rainfall on/around developing potato plants results in some consequences, such as the inability to control weeds caused by herbicide leaching, storage problems, flooding of low spots that cause plant death, and disruptions of planting and harvest schedule.Potatoes cannot respirate well when surrounded by excessive water.There is no oxygen exchange, resulting in the decay of the tissue on the inside of the potato tubers.It forms a large black circle of dead tissue at the center of the tuber, called blackheart, invisible until the potatoes have been cut open or during processing; hence, it is a silent killer [95].

Carbon level
According to the literature, CO 2 is crucial for growing potatoes and positively affects their development and growth.Many studies claim that despite increased CO 2 causing the greenhouse effect, it does not endanger the growth and development of potatoes.The primary benefit of elevated CO 2 to the potatoes is increased photosynthetic rates.It increases their growth rates by deliberately enriching potatoes with increased CO 2 .The potatoes could supply photosynthate to the tubers and bulk faster [37,[102][103][104]109].

Sunshine
Sunshine, known as solar radiation, is vital to potato germination and development.Potatoes stunt when there is a lack of sunshine [86,87,100,104,106,107]. Sunlight absorbed by potato plant leaves is an energy source for photosynthesis to increase its' surface temperature [99].The potential to absorb solar radiation depends on the leaf 's area index or surface area.Potato crops are enhanced with increased solar radiation, and the rate and quality of sunlight intercepting a canopy vary based on the season and daily cycles-Earth's tilting axis results in season changes to absorb sunlight [98].The two light components passing through a canopy are unfiltered radiation that passes and filtered radiation that is absorbed, scattered or reflected [98].It occurs mainly during the day because photosynthesis requires sunshine [99].Plant leaves utilize atmospheric CO 2 , and the roots absorb water.Water and CO 2 are converted into oxygen and carbohydrates using solar radiation.Crop biomass increases by utilizing carbohydrates from photosynthesis during plant vegetation and reproductive growth [99].

Frost
Frost is a condition involving surface (air) temperature at the earth's surface dropping to less than 0 • C [97], resulting from radiative cooling and may occur at any season of the potato development.Frost damage affects different potato species and cultivars at different temperatures [92,97], affecting the leaves, stem and cell organelles when it goes below 0 • C despite being able to withstand temperatures slightly below 0 • C. Frost causes burns and leaves withering on foliage, and in tubers, the parts frozen on the tuber can become liquid, forming a soft and blackened part.The frost effect on potato tubers results in tissue collapse on one side or end of the potato tubers close to the soil's surface.The affected tissue at the surface area dries while the tissue under the ground remains normal [90].Frost may cause a complete or partial foliage loss, reducing photosynthate production and lowering potato yields [97].Additionally, frost damage can reduce the total cultivated area for potatoes in the following season due to seed shortage [92].

Salinity
Salinization is one of the challenges in global agricultural production, and it could be the salinity of irrigation water or the soil.The salt content on the ocean surface is a crucial variable in the climate system.Temperature as a climate variable and salinity regulate how much surface water sinks into the deep ocean, which impacts long-term climate change.Salinity is influenced by ice melting caused by increased temperature and river runoff, and changes vary with the rate of evaporation and precipitation.Ocean water evaporated during the day is condensed at night as saline water on crops, determined by the rate of evaporation and precipitation [110][111][112].Aggregating high sodium ions (Na + ) concentration alters plant cell functions that enhance mineral distribution changes, respiration rate, integrity loss, and cell membrane instability.It causes a turgor pressure reduction from ion disequilibria [91].It significantly lowers potato yields and quality, affecting almost 20% of farmland and 33% of irrigated land [13,91].Fewer salts accumulate in well-drained soils than in poorly drained soils; meanwhile, as water application regularly increases with minimal leaching, salts accumulate in the root [93].

Pest and diseases
Small temperature changes and elevation of atmospheric CO 2 contribute to the rate of pest development due to increased vulnerability to organisms.The higher metabolism rate of insects affects the crop defence system.Growth, crop physiology, and life cycle of the crop's pathogens experience a direct impact.It affects pests, yields, phenology and modifications that can result in possible plant-insect interaction changes and the risk of pest infestations, which leads to interferences between natural and implemented biological control processes [68,102].Because pathogens and aphids can migrate from warmer to colder climates, any global temperature can increase pests and diseases that affect potato plants.A temperature rise increases pest pathogen pressure, increases vector activity with higher multiplication rates and results in an extended growing season with high yields [68,102].Some climatic variables contributing to the spread of severe plant disease include elevated CO 2 , drought, temperature, high humidity, cyclones, heavy and unseasonal rains, and hurricanes [102].

Assessing climate change impacts on crop yields
There are numerous ways to evaluate how the changing climate impacts crop production.Two ways outlined in this paper are statistical and agroeconomic.Statistical and process-based methods can be used to simulate potato yields.It is complex to get on appropriate spatial scales required in many global cropping systems [113].
• The statistical method uses regression analyses to estimate the production (profit) function to determine the effect of weather on the yields or profits.The evaluation depends on the data, which includes observations of various units (field, farm, county) over time [114].It can also use the cross-sectional (or Ricardian) method to analyze the connection between varying climate data and agricultural productivity measures (substituted by farmland value or revenue of the total farm revenue).Other statistical methods include ANOVA and trait correlation [115].• Analyzing using the agroeconomic method involves a combination of organizational framework, i.e. mixing biophysical (process-based) crop models with economic models for farm-level, to assess a farmer's potential in responding to adaptive measures in global climatic changes.The links between the sophisticated system, like integrated evaluations, provide the feasibility of understanding the relationship between farming and economic sectors and feedback effects [114].
Assessment of the impacts of climate change on potatoes is vital to strategizing appropriate adaptation methods for optimal productivity, and CSMs are excellent tools that can be employed.

An overview of potato CSMs
In assessing the growth development and the crop yields, different CSMs are helpful in analysis.CSMs are computer programs with dynamic simulation programs that evaluate crop growth and development through the computation of mathematical processes [116].It is a computer language that describes the relationship of crop development with the environment.Ideally, the models outline the dynamic method based on a particular hypothesis to produce a structured analysis of a crop management system [117,118].CSMs enhance research scientists/engineers to hypothesize on prolonged results of varying agricultural management and cropping processes in the agroecosystem.They widely assess the effects of agricultural practice and coping mechanisms for changing climates [119][120][121][122].A model identifies the adaptation strategy required to allow the cropping system to respond to changes possible by a model [113].The models mimic the growth of potatoes for a given set of inputs, such as weather, soil, and specific parameters [121].The potato CSM assesses factors like biomass per unit area, stage of development, nitrogen content in the canopy, and yields that show the crop state at various stages.Many studies utilize various potato crop models to evaluate potato yields to strategize adaptation practices [91,[123][124][125][126].Potato CSMs can be classified into diverse types, depending on the design and purpose; for instance, model classes could be empirical, explanatory, statistical, optimizing, mechanistic, descriptive, simulation, deterministic, static, dynamic, and stochastic models [127][128][129][130][131] or classified based on their origin (i.e. the country where they originated from [132]).We considered the process-based model because it quantitatively describes ecophysiological processes to predict crop growth and development as a function of soil-weather-crop management and is considered accurate [133,134].This review identified some CSMs used in potato studies (table 1).

Costs and benefits of CSMs
CSMs have evolved and advanced over the past three to four decades [182], monitoring the continuous irreversible increase in size and the number of crops as a result of distribution and differentiation that occurs in a plant [183].CSMs measure the daily development of crops to estimate yields at harvest, identifying the influence of climatic variables on crop growth and development [129,183].CSMs are easy to come by, cheap and fast for estimating the impacts of climate change on crop growth.Different regions and countries have used CSMs to simulate the climate change impacts on crops, e.g [77,113,118,119,121,125,128,129,132,134,178,[183][184][185][186].However, the results are based on experimental soil, plant, weather, and management data and mostly a long-time accumulation of data; hence, collecting and gathering the required data takes a long time.The DSSAT model is an example of a CSM that uses soil, plant, weather, and management data to assess the impacts of climate change on potatoes [15,19,87,100,104,106,109,124,126,187].Hijmans [86] estimated prospective potato yields with and without adaptation from 2010 to 2069 for 26 regions and countries.Without adaptation practices, only Bolivia projected an increase of 8.4%; on the other hand, 25 other countries projected a decline of 12.9% to 48.3% in potato yields.Table 2 shows countries' qualitative reviews based on solar radiation, temperature, precipitation and atmospheric CO 2 .

Decision support system for agrotechnology transfer (DSSAT)
The potential impacts of the changing climate on potato cropping are assessed using various future climate scenarios coupled with CSMs.For climate change impact assessment using CSMs, different generators of future climate scenarios with representative concentration pathways can be considered based on availability and accessibility [68,86].IBSNAT (International Benchmark Sites Network for Agrotechnology Transfer) developed DSSAT [25,87,148,[189][190][191][192].It models the impacts of soil properties, weather, genotype, management practices, water, and nitrogen dynamics [87,148].DSSAT consists of databases, modules, and applications driven by software to select and compare observed and predicted results.Based on weather, soil, crop, and genotype data from databases [148,193], the model simulates crop growth, stages of development, and yields [108].This article examines DSSAT, a modular process-based crop model with a dynamic simulation program that uses subroutines to simulate soil water and nitrogen processes in conjunction with modules for various crops [146,194,195].In more than a hundred countries, the DSSAT model has been in use for more than two decades by academics, teachers, farmers, extension agents, consultants, and policymakers [24].It comprises CSMs for over forty-two crops, supported by database programs for managing weather, soil, and planting practices and programs that initiate crop growth, plant development, and yields [146,148].DSSAT is the model's interface (figure 7), where different modules simulate input data to generate data, such as harvested yields and total yields nitrogen at harvest.The minimum datasets required to simulate with DSSAT are weather data (such as temperature, solar radiation, and precipitation), soil data (such as organic and nitrogen content and soil class), and management data (such as planting date, manure, fertilizer, and tillage), in addition, are genotype coefficients (such as potential tuber growth rate, the upper critical temperature responsible for tuber initiation) [145].SUBSTOR, as one of the sixteen computer software application programs (modules), uses Formula Translation (FORTRAN) language embedded within the DSSAT model to simulate the biomass in response to environmental factors and potato yield accumulation [124,192,196].Potatoes develop through five major stages: sprout elongation, emergence, tuber initiation, bulking, and Maturity [189].The potato's five genetic coefficients, G2, G3, P2, TC, and PD, determine how varieties react to climate change.G2 is the leaf area expansion rate (cm 2 m −2 d −1 ), G3 is the potential tuber growth rate (gm −2 d −1 ), P2 is the tuber initiation sensitivity to photoperiod (dimensionless), PD is an index of tuber growth to suppresses (dimensionless), and TC is the upper critical temperature during tuber initiation ( • C).The varying genetic coefficients impact biomass accumulation [17,106,109,124,197,198].

Challenges in using CSM for climate change impact assessment
Based on this literature, we identify the following gaps in research to be addressed in the future toward a sustainable adaptive measure to potato growth and yields.

Data availability
There is a challenge with the data available for climate change research.CSMs require soil, weather, location, and crop management data.Crop experiments that generate data required to set up and use models are rarely performed, and sometimes, data are incomplete [199].Data can be retrieved often at a cost, and formats for retrieval can vary according to the origin and kind of data [199][200][201].Furthermore, data for the same space and time scales might be scarce.Socioeconomic and physical data incompatibility are vital for climatic modeling attempts.It happens because different agencies commonly collect data for various purposes.Most studies considered only temperature in assessing the impacts of climate change while referencing the CO 2 scenarios in their literature review due to the data limitations at the time of research [199,[202][203][204][205]. Sometimes, there are faulty instruments or a lack of climate stations in some regions and sufficient data in a variable, while other variables lack sufficient data.The challenges increase when the study extends beyond an experimental field to a district, region or province [199].From the literature review,     researchers do not commonly investigate the effect of severe climatic occurrences (e.g.hails, heat, droughts, rainstorms, erosion) on potato yields because the variables are not commonly found in the CSMs.
Researchers mostly use Russet Burbank potato varieties to study the impacts of climate change on potato yields since its data is often readily available.

Modeling tools
There are some deficiencies in the modeling tools often used for climate scenario data generation to assess the climate change impacts on potato yields.Climate models are essential tools to understand better how climate changes in the past compared to the future.Model performance must continuously improve by integrating the latest chemical and physical processes technology or valuable feedback [206].[207][208][209][210].Although the latest emission scenarios are not easily accessible or in the required format, it is important to consider the latest GCMs while running the CSMs to derive an up-to-date result.Additionally, the combined effects of multiple climate variables are not being assessed despite some CSMs having the interface to combine the effects; however, the reason for not considering the combined effects has received insufficient attention, necessitating a systematic review in another paper.Moreover, a significant number of CSMs can only utilize standard climate variables such as temperature, precipitation, and atmospheric CO 2 concentration for assessment, while some variables such as salinity, frost, drought, and erosion cannot be considered.

Adaptation measures
Some adaptation strategies include adjusting to actual or predicted future climatic effects on the yields.It increases the crop's adaptability to climatic changes, such as temperature and intense extreme weather events.The most common variations in management practices for adaption to climatic change are planting dates, growth length, and water control management, which are all interdependent with technological advancements.Utilizing other adaptation measures and multiple measures at a time is mostly not explored; hence, exploration of further adaptation method analyses is being proposed for optimal production.Further, assessment could be set up with a set of climate conditions and then applied outside those climate conditions.

Discussion and conclusions
The world population currently depends on the current food system for sustainability.The global food system will determine feeding the increased population in the coming years.Meanwhile, the food system is under the pressure of the impacts of climate change, affecting the pillars of food security (access, stability, availability, and utilization) and causing food insecurity [5].This article reviews the assessment of the impacts of climate change on global potato yields to ensure food security.A CSM has the prospect of user input data to provide solutions in assessing the climate change impacts on global crop yields to provide possible adaptation strategies and management practices that are most influential on their growth under varied climate conditions to ensure stability and availability of food with easy access which people can utilize.

Figure 2 .
Figure 2. Classification of potatoes based on the quality of the tuber traits suited to processing (Texture).

Figure 4 .
Figure 4. Percentage contributions of total potato production by continents in 2018.

Figure 5 .
Figure 5. Map of potato (a) production in 2020 and (b) consumption per capita in 2018 by country.

Table 1 .
List of some widely-used potato CSMs.

Table 2 .
A literature-based summary of climate change impacts on potato yields.

Table 2 .
The frequently used GCMs to generate future climate scenarios used in the DSSAT simulation of the climate change impacts assessment is the Special Report on Emission Scenarios (SRES) used in the 2001 IPCC Third Assessment Report (TAR) and 2007 IPCC Fourth Assessment Report (AR4) from Coupled Model Intercomparison Project phase 3 (CMIP3), and the Representative Concentration Pathways (RCP) used in the 2014 IPCC Fifth Assessment Report (AR5) from CMIP5 models for the DSSAT modeling.The 2021 IPCC Sixth Assessment Report (AR6) from CMIP6 models, i.e.SSPs, is vital as the latest source of future climate scenario data for DSSAT modeling, published in the 2021 AR6 of the IPCC Jones et al 2003)used for various crops; for instance, DSSAT can simulate 42 crops, including wheat, corn, canola, cassava and others (DSSAT 2022; Hoogenboom, Porter et al 2019;Jones et al 2003).Various CSMs can simulate potato yields, considering weather, soil, and management practices data to enhance food security.The review identifies the potato's five developmental stages during germination, essential in modeling potato yields with CSMs.Climate factors that influence the growth stages and development of the potato, such as precipitation, temperature, CO 2 , solar radiation, frost, drought, and salinization, are crucial in determining the potato's growth rate.As a result, the overall growth of potatoes is affected by the distorted variable caused by climate change.Given the literature reviewed, and the research gaps deduced, further thorough study and validation with improving the crop variables and phenology are recommended in further studies to fill in the research gap on assessing the impacts of climate change on potato yields using CSMs.