The Implications of Climate Change for the Sugarcane Industry
MARTINA K. LINNENLUECKE* Faculty of Business & Economics
Macquarie University Sydney 2109 Australia Tel: +61 2 9850 9490 Fax: +61 2 9850 9481 Email: [email protected] NATALIE NUCIFORA UQ Business School The University of Queensland
St Lucia QLD 4072 Australia Tel: +61 7 3346 8115 Fax: +61 7 3346 8166 Email: [email protected] NICOLE THOMPSON Sugar Research PO Box 86, 50 Meiers Road Indooroopilly QLD 4068 Australia
Tel: +61 7 3331 3365 Fax: +61 7 3871 0383
The first author (M. K. Linnenluecke) would like to acknowledge funding from the Australian Research Council (ARC) Grand Number DP160103425
The Implications of Climate Change for the Sugarcane Industry
Abstract
This review was undertaken to draw together research on how climate change impacts sugarcane production, and to assess the implications of climate change for the sugarcane industry, as well as possible response options. Much of the extant research examines how changes in climate lead to changes in primary production; however, few studies consider how climate change translates into industry-wide impacts and economic consequences across the sugarcane value chain. Of the 90 studies we reviewed (published as journal articles, proceedings, and book chapters) 61 assess observed and/or projected impacts of climate change on sugarcane production. These studies reach largely different conclusions regarding how increases in air temperature or atmospheric carbon dioxide levels impact sugarcane production. These mixed results can be attributed to differences between the studies in terms of methods, timeframes, and growing regions, which all limit cross-study comparability. 17 studies focus on the adaptation to observed and/or projected impacts of climate change, such as changed management procedures or farming practices, but there is limited evidence regarding successful adaptation outcomes. In addition, a separate stream of papers discuss mitigating energy use and greenhouse gas emissions in the sugarcane production process, often with a view to reducing environmental impacts. Our review concludes by outlining the pathways for future research, highlighting that further insights are needed in particular regarding the economic consequences of climate change for the sugarcane industry.
Introduction
The amount of sugarcane produced worldwide is over four times that produced in 1965 and has now reached over 2 billion tons globally.1 The industry contributes significantly to gross domestic product (GDP) in major sugarcane producing economies such as Brazil, India, and China. From the late 1990s onwards, driven by growing concern about climate change and its potential economic consequences for the agricultural sector, researchers began to study the impacts of climate change on sugarcane production to better understand how projected changes in variables such as air temperature, rainfall, and atmospheric carbon dioxide (CO2) concentration influence sugarcane production.2-7 This has created a body of knowledge of how changes in climate lead to changes in the primary production of sugarcane. However, there are few studies that focus on how climate change translates into industry-wide impacts across the sugarcane value chain.8-10 Industry stakeholders and researchers have therefore started to call for a better understanding not only of how climate change impacts agricultural production, but also of the possible economic consequences resulting from climate change for specific agricultural industries.11, 12
This review was undertaken to draw together research on how climate change impacts sugarcane production, to assess the implications of climate change for the sugarcane industry, as well as possible response options. Our work has the following objectives: (1) to review evidence of how sugarcane production will be impacted by climate change and the implication this has for the sugarcane industry, (2) to review possible response options available to actors along the sugarcane value chain, and (3) to outline knowledge gaps, research shortcomings, and research priorities. The paper proceeds as follows. The following section provides a brief overview of the sugarcane industry. This is followed by a description of the review methodology via which we classified studies according to their contribution to one of three main categories: impacts of climate change, adaptation, and mitigation. The studies are then reviewed in detail based on the focus of their analysis, their approach, and their location or study region (where applicable). Summary tables outline the main findings of all studies included in the review. We conclude by outlining pathways for future research,
to better understand the links between climate change, sugarcane production, and response options for the industry sector in different countries and regions.
Background: The Sugarcane Industry
Sugarcane is a tropical plant grown in many regions of the world. Figure 1 maps production quantities of sugarcane by country to illustrate the extent and distribution of sugarcane production. The map shows that the top sugarcane producing countries are Brazil, India, China, Thailand, Pakistan, and Mexico, followed by other countries such as Australia and the United States. Sugarcane is an important crop for the production of raw sugar, a bulk commodity with minimal product differentiation which is usually sold at market value.9 The industry value chain for the production of raw sugar involves growing the sugarcane, harvesting annually, and transporting, milling, and refining, as well as the storage, marketing, and onward distribution to wholesalers and end consumers.8, 9, 13 However, there are a number of notable differences between sugarcane value chains across countries, in particular regarding farm sizes, ownership structure, and mechanization. In countries such as Australia and South Africa, sugarcane farms are mostly privately owned and between 20 and 200 ha in size. In other countries (e.g., Brazil and the United States) sugarcane farms are predominantly owned or controlled by milling companies.9, 14 Harvesting takes place by hand cutting or through mechanical harvesting, with the latter being common in developed countries.9 The sophistication of onward transportation, milling, marketing, and distribution also varies significantly from country to country. In developed sugarcane growing countries (e.g., Australia, Brazil, the United States), a sugar mill processes between 1,000,000 and 5,000,000 tons of cane per year,9 while less developed regions have much smaller production capacity. In countries such as China, raw sugar production tends to be targeted at domestic markets, while in other countries (e.g., Australia) production is primarily for export.9
The conversion of sugarcane into raw sugar creates several by-products including biofuels, bioenergy, bioplastics, paper, animal feed, and fertilizers.4 In recent years, there has been considerable investment internationally in the production of biofuel from sugarcane. Current estimates suggest that the share of sugarcane allocated to ethanol production will
increase to 26% in 2024 (from 20% during the base period 2012–2014). Brazil is the pioneer in producing biofuel from sugarcane – the country has a long history of supporting biofuel consumption and has adopted policies to encourage biofuel production, leading to an increase in biofuels (including those produced from sugarcane) from the 1970s onwards. In 1975, Brazil instituted the “Proalcool” program in response to the first oil crisis. This program provided incentives for sugarcane ethanol production and helped make Brazil a leading producer of ethanol sugarcane.16 Other countries such as the Philippines have only more recently implemented biofuel production programs.17 Sugarcane ethanol production leads into a different post-mill value chain, which typically includes fermentation, distillation, and onward distribution through channels similar to those for conventional fuels.13 However, the expansion of sugarcane production for biofuels has become a contentious issue.18 On the one hand, biofuels are a possible alternative to fossil-fuels; on the other hand, a growing biofuel industry has implications for land use patterns, biodiversity, and food security.19
--- Figure 1 about here ---
The sugarcane industry is also the subject of other environmental and social concerns. Environmental concerns arise from the industry’s use of fertilizers and herbicides, and water for irrigation, with the associated problems of runoff and nutrients leaching into waterways and oceans. These lead to negative ecosystem impacts, such as poorer water quality, eutrophication, and a loss of biodiversity.20, 21 Social concerns arise from the working conditions of sugarcane workers, especially in developing countries, and the health risks from intense physical labor in high temperatures, exposure to pollutants, and harmful effects of sugarcane burning. Albeit, it is worth noting that this traditional harvesting practice is now regulated in many sugarcane-growing countries.22
For decades, the global raw sugar industry has contended with a long-term downward price trend (50% decrease over the 35-year period to 1999); 9 however, recently the market has been characterized by price spikes and increased volatility. The world sugar priced soared to a high in early 2010 and 2011 before declining again until late 2015 and then climbing
again in 2016. The reasons for this price volatility are related to Brazil’s role in energy markets as well as exchange rate dynamics, which put upward pressure on global prices. In addition, the world sugar price has been significantly impacted by political factors such as changing economic incentives for sugarcane production, as well as supply shortfalls due to weather disruptions.23
Methodology
We identified relevant papers for inclusion in this review through Boolean searches within the Web of Science, an online academic citation database within the Thomson Reuters
(formerly ISI) Web of Knowledge platform. We searched for studies with the terms “climate
change”, “global warming”, “weather extreme*”/“extreme weather”, and “greenhouse gas*” in the title, abstract, or keywords. To retrieve only papers relevant to the sugarcane industry, we limited the search to publications that also included “sugarcane”, “sugar cane” or “sugar” in the title. The asterisk symbol (*) was included as a wild card to allow for plural forms of the search terms. Our initial search resulted in 228 records (as of January 2017). We then manually reviewed these records—two of the authors screened the titles, abstracts, and full texts of each publication to determine its suitability for inclusion in this review.
We removed papers which matched the search parameters, but addressed different topics (e.g., changes in the sugar content of grapes due to climate change). We also decided to exclude papers which focused solely on the topics of (bio)ethanol or (bio)energy production (62 records), because these papers tend to consider fuel production processes and renewable energy sources more broadly. Excellent reviews on these and related topics are available elsewhere.24-27 However, our review does discuss increases in ethanol demand and political responses in different countries, as these developments influence demand and consumption patterns for sugarcane. In addition, we decided to exclude papers focusing solely on soil management practices, but note that some of these papers refer to the environmental consequences of improper management practices and the high potential for greenhouse gas (GHG) emissions (especially nitrous oxide) from soils.28-30 In total, 51 articles of the 228 records were deemed to contain evidence relevant to this review.
To ensure that the search was comprehensive, we conducted a cited reference search (studying the references cited by the retrieved papers) to find studies related to our topic of interest that may have been missed during the initial search. We included studies which specifically address climate change, rather than papers that discuss responses to irrigation or weather conditions more generally.8, 31 To complement the search, we also accessed resources through collections in the Sugar Research Australia (SRA) eLibrary, which holds a broad collection of international and other relevant publications. Through these steps, we found 27 additional studies which were also included. Relevant insights on climate change and the sugarcane industry have also been published as book chapters,32, 33 in the Proceedings of the International Society of Sugar Cane Technologists (ISSCT),10, 34-37 the Australian Society of Sugar Cane Technologists (ASSCT),11, 38 as well as the Proceedings of the South African Sugar Technologists Association.39-42 One paper was excluded from further analysis because the full text was not available.37 This brings the total count of studies included in this review to 90.
We sorted the studies according to their main contribution and topic area. Of the 90 studies, 61 describe observed and/or projected impacts on sugarcane production arising from changes in climate variables, such as increases in air temperature or carbon dioxide levels. However, there are very few studies (only 17) which consider how actors within the sugarcane industry adapt to climate change (eight adaptation studies are listed twice in the analysis sections as they fit both the impact and adaptation categories). A further 20 studies explore the mitigation of energy use and GHG emissions in the production of sugarcane. Each of these topic areas is reviewed in greater detail below. For completeness, we also acknowledge a range of insights published in industry reports and associated documents. These include work on the impacts of weather and climate change on sugar production (including work linking different future scenarios and crop models),43-49 as well as lifecycle analysis and carbon footprinting studies.50-52
Impact Studies
A first set of studies outlines the observed and/or projected impacts of climate change on sugarcane production. As detailed in the following sections, the reviewed papers are very diverse in terms of methodologies, timeframes, and the geographic location of the study sites (resulting in differences in local factors, such as rainfall and temperature). Consequently, it is not possible to directly compare the findings regarding how climate impacts sugarcane yields or other aspects of sugarcane production (e.g., harvest). Likewise, no single study fully captures the range of possible climate change impacts for any particular region and simultaneously offers strategies to mimize resulting negative consequences (or enhance consequences if they were positive).
Table 1: Impact Studies
Reference Impacts Assessed Approach Crop Model GHG
Scenario GCM/RCM Simulation timeframe Location Key Findings
Australia - Impacts of climate change on sugarcane production
Everingham
et al. (2015)4 Impacts of climate change on
sugarcane yield Crop modelling Yields are simulated using a combination of Canegro and WaterSense, a web-based irrigation water optimization tool; other aspects (leaf canopy development, radiation interception, biomass accumulation) are based on APSIM-Sugarcane; use of multiple sets of model parameterisations B1 and A2 scenarios, with and without elevated CO2 Ensemble of 11 GCMs from CMIP3, downscaled 2046-2065 Burdekin, Mackay, and New South Wales
Climate change is expected to have neutral or positive impacts on sugarcane production, but industry should not overlook negative impacts
Sexton et al., (2014)42 Sexton et al., (2015)7
Impacts of climate change on
harvestability Modelling of unharvestable days based on daily rainfall simulations
N/A B1 and A2
scenarios Daily rainfall simulations for an ensemble of 11 GCMs from CMIP3, downscaled 2046-2065 Regions between the mountain ranges and narrow eastern coastline
Climate change is expected to lead to a decrease in the number of unharvestable days for the
Burdekin/Bundaberg regions, but to an increase for the Herbert region under the A2 scenario
Park et al.
(2010)32 Impact of climate change on the Australian sugar industry and adaptation options
Review of existing research
N/A N/A N/A Not specified Australia The greatest direct climate change impact for Australian sugarcane production is likely the projected change in the amount, frequency, and intensity of future rainfall
Park (2008)11 Impact of climate change on the Australian sugar industry and adaptation options
Review of existing research
N/A N/A N/A Review of
research conducted over 2004-2008
Australia The most effective way to assess the impacts of climate change is to conduct climate assessments in collaboration with stakeholders
Scenario timeframe Park et al.,
(2007)10 Impact of climate change on the Australian sugar value chain Qualitative assessment, crop modelling APSIM Effect of CO2 on sugarcane physiology was not considered
CSIRO 2030 Rocky Point (south) and Mossman (north)
Yield losses are likely be greater in the cooler southern regions due to increased water stress
Park and Attard (2005)38
Impact of climate change on the Queensland sugar industry and adaptation options
Review of existing research
Cites APSIM, but the
paper is conceptual Not specified CSIRO 2030, 2070 Queensland The net effects of climate change impacts are unknown and may vary between regions Liu and Bull
(2001)54 Development of a crop simulation model (QCANE) to simulate cane growth and sugar accumulation
Crop model development and validation
QCANE model N/A N/A N/A Queensland, verification sites: Ingham, Bundaberg
QCANE simulates photosynthesis which might make the model more flexible for simulating the impacts of climate change and increasing CO2 levels on sugarcane production compared to other models
Chakraborty et al. (1998)55
Impact of climate change on plant diseases (wheat/grains, fruits, grapes, vegetables, sugar)
Conceptual N/A IS92a-f Generic reference to GCMs and CSIRO
2100 Australia Climate change may reduce/increase or have no effect on certain diseases, but further research is needed
Australia - Impacts of runoff on the Great Barrier Reef
Biggs et al.
(2013)56 Impact of sugarcane farming on the Great Barrier Reef Crop modelling APSIM B1, A1B and A1FI scenarios
3 GCMs,
downscaled 2030 Mackay Without any interventions, the frequency of years with very high N losses could increase by 10-15%; improved farming practices may more effectively limit nitrogen losses than traditional practices
van Grieken
et al. (2013)57 Impact of agricultural water improvement strategies on communities Socio-economic and crop modelling Environmental Economic Spatial Investment Prioritization (EESIP) model with APSIM as a component
Not
specified Not specified Not specified North Queensland (Tully-Murray catchment)
Desired water quality improvement targets increase the risk of mill closure, discusses both climate change and pollutant loads as risks to the Great Barrier Reef
Webster et al.
(2013)58 Expected climate change impacts on nitrogen loss from wet tropical sugarcane production in the Great Barrier Reef region
Crop modelling APSIM 425-449 ppm in 2030 and 518-702 ppm in 2070
Not specified 2030, 2070 North Queensland (Tully-Murray catchment)
The impact of potential climate change is likely to be small in comparison to the impacts of management practice change
Scenario timeframe Haynes et al.
(2007)59 Impact of chemical runoff from the sugarcane and cattle industries on the Great Barrier Reef
Conceptual N/A N/A N/A Not specified North
Queensland The paper develops a detailed conceptual model that links anthropogenic pressures (dry-land cattle grazing, intensive sugar cane cropping) to impacts on the water quality of the Great Barrier Reef
Brazil - Impacts of climate change on sugarcane production
de Carvalho et al. (2015)6
Impacts of climate change on sugarcane yield Crop modelling Century 4.5 model A1B Eta/CPTEC-HadCM3 2014-2040, 20412070 -2071-2100
Pernambuco Climate changes might reduce the potential sugarcane yield in north-eastern Brazil
Marin et al.
(2015)60 Analysis of APSIM-Sugar and DSSAT-Canegro to determine structural differences and how they affect projections of crop growth and production
Crop modelling APSIM-Sugar and
DSSAT-Canegro The authors consider variation in rainfall (±30%), air CO2 concentration (350ppm-750ppm) and air temperature (-3 to +9°C) using the historical climate of the sites as baseline (1980-2010) Field data from seven sites in Brazil to parameteriz e models
The mean of simulations from both models produced better estimations than prodictiong from either the APSIM-Sugar or DSSAT-Canegro model. Researchers should apply the two models to improve projections
Marin et al.
(2014)61 Plant responses to climate change Crop modelling, set of field experiments
DSSAT-Canegro The authors consider variation in rainfall (±30%), air CO2 concentration (350ppm-750ppm) and air temperature (-3 to +9°C) using the historical climate of the sites as baseline (1992-2007)
Two sites in
São Paulo Process-based crop models can be improved by better incorporating findings from plant physiology, in particular regarding CO2 effects on plant
photosynthesis and water use dos Santos
and Sentelhas (2014)62
Impacts of different climate change scenarios on water balance and sugarcane yields
Crop modelling Agrometeorological
model A1T, A1B, and A1Fl Not specified, the authors create 12 climate scenarios
2030, 2060,
2090 Southern Brazil, four main cane regions in São Paulo
Even with the impact of climate change on water availability, potential and actual yields may increase substantially (between 59-82% by 2090 in São Paulo), also as a result of better management practices Marin et al.
(2013)63 Impacts of climate change on
sugarcane yield Crop modelling DSSAT-Canegro A2 and B2 PRECIS and CSIRO, downscaled
2050 Southern
Brazil Projected yields could be up to 59% higher than the current state average yield Marin and de
Carvalho (2012)64
Analysis of how climatic factors and soil effects impacted sugarcane yield efficiency and yield gap throughout 16 growing seasons
Crop modelling Empirical model
(statistical analysis) N/A N/A 1990/1991 to 2005/2006 São Paulo Climatic factors explained 43% of the variability of sugarcane yield efficiency, while soil explained 15% of the variability
Scenario timeframe dos Santos
and Sentelhas (2012)65
Impacts of climate change on the water balance of sugarcane production areas
Water balance
simulations N/A A1T, A1B and A1Fl Not specified, the authors create 12 climate scenarios
2030, 2060,
2090 São Paulo Soil water availability will be reduced in all locations by 2090
Gouvêa et al.
(2009)66 Impacts of climate change on sugarcane yield Crop modelling Agrometeorological model A1B Not specified, the authors create 21 climate scenarios
2020, 2050,
2080 Southern Brazil Higher air temperatures will increase the potential productivity while changes in solar radiation/rainfall will have less impact
Brazil - Impacts of climate change on sugarcane expansion
Georgescu et
al. (2013)67 Potential hydroclimatic impacts of projected Brazilian sugarcane expansion
Modelling of hydroclimatic consequences
Weather and Research Forecasting (WRF) modelling system
N/A Noah land surface model in WRF
2004-2008 Brazil Results indicate a cooling of up to ~1.0°C during the peak of the growing season, largely because of increased albedo
Loarie et al.
(2011)68 Direct climate effects of sugarcane expansion in Brazil Analysis of satellite and vegetation data
N/A N/A N/A 2005-2008 Brazil Results indicate that there is a direct local cooling effect from expanding sugar cane into existing crop and pasture land
Sparovek et
al. (2009)69 Environmental, land-use, and economic impacts of Brazilian sugarcane expansion 1996-2006 Analysis of environmental and economic data
N/A N/A N/A 1996-2006 Brazil Sugarcane expansion did not generally contribute to direct deforestation in the traditional region where most of the expansion took place, but was related to deforestation in the Amazon and the Northeast region
Africa - Impacts of climate change on sugarcane production
Jones and Singels (2015)5 Jones and Singels (2014)39
Impact of mid-century climate change on sugarcane yields and sucrose yields
Crop modelling DSSAT-Canegro
(modified) 571 ppm 5 GCMs from CMIP5, downscaled
2040-2070 South
Africa Medium-term (moderate) climate change could be largely positive for the South African sugar industry
Jones et al. (2013, 2015)3, 41
Impact of climate change on water use and yield of irrigated sugarcane
Crop modelling DSSAT-Canegro 734ppm (A2 scenario) 3 GCMs from CMIP3, downscaled 1980-2010
2070-2100 South Africa Climate change may increase sugarcane yields in South Africa by 11%, but reduce cane quality and sucrose yields and increase irrigation needs Chandiposha
(2013) 70 Impact of climate change on sugarcane production and adaptation options
Review paper N/A N/A N/A Not specified Zimbabwe Increases in air temperature may lead to increased cane growth during winter, but may also increase irrigation needs, with effects on the prevalence of weeds and pests.
Scenario timeframe Knox et al.71
(2010) Impact of climate change on sugarcane Crop modelling DSSAT-Canegro A2 and B2 HadCM3, downscaled 2050 Swaziland Future irrigation needs are predicted to increase by 20-22%; with increased atmospheric CO2 levels the net annual irrigation water requirements are predicted to increase by 9%
Deressa et
al.72 (2005) Impact of climate change on sugarcane production under irrigation and dryland conditions
Ricardian
model N/A doubling of carbon dioxide
N/A Baseline data: 1977-1998
South
Africa Climate change has a significant nonlinear impact on net revenue per hectare with a higher sensitivity to increases in air temperature than precipitation. Irrigation is not an effective adaptation measure. Gbetibouo
and Hassan (2005)73
Impact of climate change on
field crops (incl. sugarcane) Ricardian model N/A doubling of carbon dioxide
N/A Baseline
data: 1993 South Africa The production of field crops is sensitive to marginal changes in air temperature as compared to changes in rainfall. Climate change impacts are not uniform and might require distinct shifts in farming practices.
Comparative Studies, Other Regions – Impacts of climate change on sugarcane production
Sengar et
al.33 (2015) Impact of climate change on sugarcane productivity Conceptual N/A 730-1020 ppm by end of century
N/A N/A India There is a need to further understand and detail physiological traits before designing a strategy to optimise sugarcane improvement
Jones et al.40
(2014) Evaluation of DSSAT-Canegro for simulating climate change impacts at sites in seven countries
Crop modelling DSSAT-Canegro The authors consider variation in rainfall (-25, -10, 0, +10, and +25%), air CO2 concentration (+90, +190, +290, and +390 ppm) and air temperature (-3, 0, +3, +6, and +9°C) using the historical climate of the sites as baseline
Seven
countries Model testing should occur globally in diverse environments and production scenarios; local testing may lead to model-fitting by unwanted parameter adjustments
Singels et al. (2013, 2014)74, 75
Predicting climate change impacts on sugarcane production
Crop modelling DSSAT-Canegro 734 ppm (A2 scenario)
3 GCMs from CMIP3, downscaled
Not specified Australia, Brazil, and South Africa
Cane yields could increase under future climates (+4% for Ayr/Australia, +9 for Piracicaba/Brazil, and +20% for La Mercy/South Africa)
Kumar and Sharma (2014)76
Impact of climate change on
sugarcane productivity Linear regression, Ricardian model, Cobb-Douglas model
N/A N/A N/A Baseline
data: 1980-2009
India There is a non-linear relationship between climatic factors and sugarcane productivity
Black et al.
(2012)77 Cultivating sugarcane in Ghana under a changing climate Crop modelling Joint UK Land Environment Simulator with formulations from Canegro
345 ppm,
690 ppm N/A 1984-2008 Ghana (Africa), São Paulo (Brazil)
Provided there is sufficient irrigation, it is possible to generate approximately 75% of the yield from São Paulo. A doubling of atmospheric CO2 levels mitigates the degree of water stress associated with a 4°C increase in air temperature.
Scenario timeframe Cuadra et al.
(2012)78 Development of a new process-based sugarcane model Crop model development and validation
Crop model for use within the Agro-IBIS dynamic agro-ecosystem model
N/A N/A Not specified São Paulo (Brazil) Louisiana (US)
The model developed in the article can be applied to the simulation of climate change scenarios (however this was not done in the article)
Knox et la.
(2012)79 Climate change impacts on crop productivity in Africa and South Asia
Review and
meta-analysis N/A N/A N/A 2050 Africa and South Asia There are only a limited number of studies on sugarcane which does not allow to conduct a meta-analysis for climate impacts on sugarcane Singh et al.
(2010)80 Evaluation of the Canegro model in an Indian context Crop modelling DSSAT-Canegro N/A N/A Not specified East Uttar Pradesh (India)
The Canegro model satisfactorily simulates the potential growth and yield of sugarcane crop and has future use in the projection of climate impacts da Silva et al.
(2008)81
Effects of elevated atmospheric CO2 on sugarcane growth and development
Design of crop
model Based on Barbieri (1993) Field experiment: doubling of CO2; simulation: A2 and B2 Reference to GCMs from the SRES report 2060, 2070 São Paulo (Brazil) and Queensland (Australia)
Sugarcane productivity will increase up to 13% by 2070 in both countries
Gawander
(2007)82 Impacts of climate change on sugarcane production Conceptual N/A N/A N/A Not specified Fiji The impacts of extreme events and resulting effects on sugarcane production are of great concern Jintrawet and
Prammanee (2005)35
Impacts of climate change on
sugarcane production Crop modelling DSSAT-Canegro doubling of carbon dioxide
CCAM model 2006-2024 Mekong River Basin (Thailand)
Climate change has a positive influence on sugarcane fresh yield, but leads to a lower sugar yield per ton of sugarcane fresh yield
Nayamuth
(2005)36 Climate change impacts on sugarcane yield in Mauritius and adaptation options
Review paper, refers to another study (Ref. 34) Refers to Ref. 34 which
uses APSIM Refers to Ref. 34 CCCM, GFDL, GISS, UKMO
Refers to
Ref. 34 Mauritius Refers to findings presented in another study (Ref. 34 ) Cheeroo-Nayamuth and Nayamuth (2001)34
Climate change impacts on sugarcane yield in Mauritius and adaptation options
Crop modelling APSIM doubling of carbon dioxide CCCM, GFDL, GISS, UKMO Baseline data: 1954-1996, timeframe for climate change not specified
Mauritius Sugarcane yields will be reduced due to lower water use efficiencies and higher respiratory demands under various climate change scenarios.
Singh and El Maayar (1998) 83
Effects of climate change on
sugar cane yields Crop modelling Photosynthesis-based model doubling of carbon dioxide
N/A Not specified Trinidad
and Tobago There will be significant decreases in sugar cane yields (20-40%), mainly due to an increasing occurrence and severity of soil moisture stress
Scenario timeframe Phalan et al.
(2013)84 Impact of expansion of cropland in tropical countries Analysis of cropland data N/A N/A N/A 1999-2008 Tropical countries More effective sustainability standards and policies need to address both production and consumption
Comparative Studies, Other Regions – Social impacts of climate change
Crowe et al. (2009, 2010, 2013, 2015)85-88
Heat exposure of sugarcane
workers Observation, heat stress measure
N/A N/A N/A Present day Costa Rica These studies investigate occupational heat stress as an important potential consequence of climate change and suggest that actions are warranted to improve working conditions (hydration, shade, rest)
Other – Experiments and Conceptual Work
Stokes et al.
(2016)89 Effects of CO(crop growth) 2 on sugarcane Glasshouse and field experiments, modeling with customised version of WaterSense N/A 390 ppm,
720 ppm N/A N/A Location for field experiment: Ayr (Australia)
The study seeks to disentangle the mechanisms of CO2 response and separates direct and indirect effects of CO2 on crop growth; presents evidence that future modelling approaches should represent CO2responses predominantly through indirect water-related mechanisms
Baranoski et
al. (2012)90 In silico assessment of the impact of various stress factors (limited water, nutrient supplies) on C4 plants to test possible climate change impacts
In silico
experiments N/A N/A N/A N/A - Abiotic stress factors affecting the photosynthetic apparatus of C4 plants have a direct impact on their agricultural yield
Allen et al.
(2011)91 Impact of elevated COtemperature on growth and 2 and sugar yield of the C4 sugargane
Experiment N/A 360 ppm,
710 ppm N/A N/A - The productivity of the C4 sugarcane should be enhanced by future increases in atmospheric CO2 Ghini et al.
(2011)92 Review of methods to evaluate the impact of climate change on diseases of tropical and plantation crops
Conceptual N/A Reviews other studies that look at various GHG scenarios N/A Reviews other studies that look at 2020s, 2050s, 2080s Cites evidence from several locations
Suggests experimental and analytical approaches to advance knowledge, makes a case for studies under realistic field conditions
Scenario timeframe Jaggard et al.
(2010)93 Impact of climate change impacts and technological advances on changes in arable crop yields by 2050
Conceptual N/A 550 ppm N/A 2050 Cites evidence from several locations
By 2050, the increase in atmospheric CO2 will not increase the yields of C4 species; climate change will reduce plant water consumption; however, this effect is likely cancelled out by increased evaporation rates; there are concerns about the impacts of extreme events Vu and Allen
(2009)94 Impact of elevated atmospheric CO 2 and drought stress on sugarcane leaf photosynthesis
Experiment/
field trial N/A 360 ppm, 720 ppm N/A N/A Gainesville, Florida (US) Sugarcane grown at elevated atmospheric COproperties which helped to delay the adverse effects of 2 had drought
Vu and Allen
(2009)95 Impact of elevated atmospheric CO 2 and high air temperature on sugarcane
Experiment N/A 360 ppm,
720 ppm N/A N/A Gainesville, Florida (US) Sugarcane plants grown for 3 months at a combination of doubled atmospheric CO2 and high air temperature accumulated more leaf area, leaf, and stem biomass than counterpart, also had greater stem juice production
De Souza et
al. (2008)96 Impact of increased atmospheric CO
2 concentration on sugarcane
Experiment N/A 370 ppm,
720 ppm N/A N/A São Paulo (Brazil) Sugarcane crops grown under elevated atmospheric CO2 increase photosynthesis, biomass and productivity, and show modified gene expressions Vu et al.
(2006)97 Impact of increased atmospheric CO
2 concentration on sugarcane
Experiment N/A 360 ppm,
720 ppm N/A N/A Gainesville, Florida (US) COenhancement in leaf area, plant biomass accumulation, 2-enriched sugarcane plants might show an and sucrose production
Impacts Assessed
The impact studies concentrate on the impacts of climate change in three sugarcane regions (see Table 1): Australia, Brazil, and Africa (mainly South Africa). Several comparative studies assess differences and similarities between Australia, Brazil, and/or South Africa. Very few findings are available for other major sugarcane regions such as India, Thailand, China, Pakistan or Mexico. A common aim among studies is to assess the impacts of climate change on sugarcane production (typically measured in terms of yield losses or yield gains) (22 studies). Other topics covered include the impact of climate change on crop harvestability,7, 42 plant diseases,55, 92 water availability, and impacts on the sugar industry more generally.10, 11, 32, 38 Studies have also sought to understand how well different models simulate the impacts of climate change on sugarcane growth and production.40, 60, 61, 98 Some studies are concerned with the social and environmental impacts of sugarcane production, including the risks to sugarcane workers of heat exposure (in Costa Rica),85-88 and the negative environmental consequences of expanding sugarcane landholdings in Brazil and tropical countries in general67-69, 84 (e.g., sensitive ecosystems such as the Great Barrier Reef). 56-59
A large proportion of impact studies focus on the physiological responses of the crop to climate change, rather than industry-wide impacts in terms of production changes, economic gains/losses or changes in supply patterns. Exceptions are studies by Park and colleagues10, 11, 32, 38 who offer a discussion on industry-wide consequences of climate change in Australia, and call for a greater collaboration with stakeholders to better understand climate risks across the sugar value chain. In addition, there is also not much research that details response options by actors such as growers or mills. Most of the 61 impact studies assess climate impacts on sugarcane production only; just eight simultaneously examine climate change impacts and adaptation (see also section on ‘Adaptation Studies’). Some studies make implicit assumptions about adaptation to climate change and consider farm management practices, such as changes in irrigation.4 However, these studies not not explicitly model a range of likely adaptation alternatives. The diversity in topics covered certainly reflects the range of possible climate impacts. Nevertheless, research needs to more
fully examine the impacts of climate change beyond yield gains or losses, and to do so in conjunction with the other social and environmental impacts associated with sugarcane farming and agriculture in general.99
Methods to Assess Climate Impacts
Approaches for assessing the biophysical impacts of climate change on crop yields include statistical analyses, experimental studies, agro-ecological models, and process-based dynamic crop growth models. These methods have also been used to evaluate the impacts of climate change on sugarcane (see Table 1).100 Statistical models use historical crop yield data to predict future yield responses to variations in climate variables, and can be based on time series data (i.e., data from a specific growing site over time), panel data (i.e., data from multiple sites over time), and cross-sectional data (i.e., data from across growing regions).101 The advantage of statistical analyses is they do not rely on field calibration data. However, they do raise issues such as dependence among predictor variables, reliance on past data to predict future outcomes, and low signal-to-noise ratios in weather and yield records for many sites.101 Experimental studies seek to establish how crop growth is affected by factors such as elevated atmospheric CO2 concentrations and higher air temperatures.89, 91 Experiments allow researchers to control factors of interest and can thus provide input for modelling studies,89 but are limited to artificial settings. Agro-ecological models estimate the magnitude of differences between maximum potential crop yield and actual yields,102 while process-based dynamic crop growth models simulate crop growth, development, and yield as a function of variables such as climate, soil conditions, and management practices.103-105 A main issue with all modelling efforts is whether a given model provides realistic simulations for a given environment.60 Nonetheless, crop models have been widely used in agricultural research and management as they can simulate diverse issues such as crop management, soil impacts, climate impacts, and issues related to crop adaptation and breeding.105 Modelling results can
be evaluated through comparisons with observed values and/or results from experiments or simulations that assume different conditions.99, 106
Several process-based models have been specifically developed for simulating sugarcane production and include the now widely-used Agricultural Production Systems Simulator (APSIM) Sugarcane model107 and the Canegro model.108, 109 Researchers have also developed region-specific models, such as the Australian QCANE98 and ‘AUSCANE’110 models, but the APSIM-Sugarcane and DSSAT-Canegro models are more widely adopted.61 These models reflect how sugarcane crops respond to factors such as temperature, solar radiation, precipitation, soil type, soil water balance, and other parameters influencing plant growth and development (e.g., fertilizer use, irrigation, and other management practices). 104-106, 111 Crop models are typically modified to provide better outcomes for specific cultivars in specific environments.106 The extant literature extensively discusses the differences between the various sugarcane models, as well as their respective strengths and weaknesses.60, 112
As evident from Table 1, crop modeling is the dominant approach to determining climate impacts on sugarcane production (26 studies, at times in conjunction with other approaches). Many crop modelling studies employ the DSSAT-Canegro model (nine studies) or the APSIM framework (five studies); but others use agro-ecological models (two studies) or different sugarcane models. Crop models allow researchers to simulate the impacts of climate change on crop production by inputting climate data (e.g., atmospheric CO2 levels, air temperature, rainfall) corresponding to future GHG emission scenarios of interest.99 Thus, these models offer a flexible approach to predicting the potential impacts of climate change on future crop production, beyond simple statistical extrapolation of past data. However, given that models can only provide approximations, there are uncertainties inherent in forecasting climate change impacts on sugarcane production.60, 113 These uncertainties arise from several sources, including differences in the structures and parameter values of the sugarcane models used for the analysis; and uncertainties regarding future emission trajectories, the effects of emissions on climate change, and the downscaling of climate data (see also next section).114 As shown in Table 1, assumptions regarding future GHG emission scenarios vary between studies. The studies themselves also vary in terms of the general
circulation models (GCMs) or regional climate models (RCMs) used, as well as the approach to downscaling to specific locations. Few studies use ensembles of multiple GCMs. In addition, crop modelling studies have been criticised for making oversimplified assumptions (e.g., regarding responses to heat stress) and for having limited field data regarding crop responses to climate change.99
Fewer studies report on experiments, statistical models, or conceptual insights, or review existing research. Findings from controlled experiments suggest that there are overall positive impacts of elevated atmospheric CO2 levels on sugarcane growth, including increased biomass, water use efficiency, photosynthesis, and productivity.91, 94, 95, 97 Researchers have carried out experimental studies to improve the assumptions underlying crop models regarding the response of sugarcane yields to future rises in atmospheric CO2 concentrations. Findings from recent experimental studies suggest that modelers need to carefully consider the assumptions used for modelling, in particular for representing CO2 effects in crop models.89
The findings presented in Table 1 are very diverse, making it difficult for stakeholders to interpret and synthesize the results. The challenges associated with using current findings as the basis for policy or production decisions become evident when looking at the impact studies for Brazil, as an example. Some of these studies report significant yield losses in some regions, while others describe significant yield gains in other regions due to elevated atmospheric CO2 levels associated with climate change. For Pernambuco (a northeastern region in Brazil), de Carvalho et al.6 conclude that potential sugarcane yield will be reduced in both the near and distant future (until 2040 and 2100, respectively) due to reduced rainfall levels. However, other studies (e.g., dos Santos and Sentelhas62) suggest that yield increases could be as high as 59-82% by 2090 in the State of São Paulo (a southeastern region in Brazil), and attribute yield increases to the combined effects of higher air temperatures, higher atmospheric CO2 concentration, and changing management practices. For the purposes of agricultural decision-making, these findings suggest that sugarcane production and expansion should take place mostly in southeastern regions to capitalize on yield gains. However, we cannot confidently adopt any such recommendations without verifying the
work in additional studies, considering how any industry expansion would affect local communities and ecosystems, and clarifying the extent to which study results diverge due to the use of different methods, scenarios, and models.99
Uncertainties
Uncertainties inherent in modelling the potential impacts of climate change on agricultural productivity have prompted researchers to call for more robust modeling approaches, and more coordinated data sources and model intercomparisons to improve the reliability and validity of results.4, 99, 115 One possible approach for reducing uncertainties has been developed by the Agricultural Model Intercomparison and Improvement Project (AgMIP, see www.agmip.org), a major international and transdisciplinary initiative that has fostered (1) links between climate, crop and economic models, (2) the use of model ensembles to understand prediction uncertainty, and (3) the use of standardized model implementation protocols to allow intercomparison and reduce prediction uncertainty.53, 74, 75, 100, 116 The use of multi-model ensembles allows to better characterize uncertainty due to multiple GHG emissions pathways, climate models, and crop impact models.100, 114 Focusing specifically on sugarcane models, researchers have also argued that multiple models should be used to assess the impacts of climate change on sugarcane growth and production to improve the reliability and validity of findings across a range of soil types, climates, and sugarcane cultivars.60
Researchers have also voiced concern that existing studies do not fully consider the long-term negative effects of climate change, including adverse impacts on nutrient levels as well as decreases in soil moisture as higher temperatures increase evapotranspiration rates.2 In addition, there are concerns that current studies might significantly overestimate the potential benefits of climate change (and underestimate adaptation needs) by not taking full account of the range of climate change threats to agricultural production, such as more volatile weather extremes, risks of disease, and limits to water availability.2 In the past, sugarcane yields have been significantly impacted by extreme weather events such as drought and tropical cyclones, and changes in the frequency and/or intensity of weather extremes due to climate change could exacerbate impacts.82 For example, it is estimated that Cyclone
Larry, which made landfall in Queensland, Australia in 2006, affected over 60% of all growers in its path and led to a loss of A$111 million in raw sugar output in the 12 months following the initial impact.117 The cyclone negatively affected sugarcane producers (e.g., impacts on growing areas, and yield losses) and sugarcane mills (e.g., impacts on infrastructure, and decreased output), and led to the decision not to open the Mourilyan sugar mill for the 2006 crushing season. The mill did not recover and remained permanently closed. The same region was also affected by Cyclone Yasi (2011) and Cyclone Debbie (2017). Any increased cyclone intensity due to climate change could considerably exacerbate impacts in this region,118 but is currently not explicitly factored into existing sugarcane models.
In addition, the question of how climate change influences sugarcane disease patterns has not yet been fully explored,55 and few studies examine how climate change impacts the sugarcane industry when accounting for other threat factors (e.g., biodiversity loss, land-use change, freshwater use, pollution).67-69, 119 Some studies argue that the impacts of climate change on ecosystems such as the Great Barrier Reef in Australia need to be assessed in conjunction with the impacts of nitrogen losses from sugarcane production to fully understand the interactions between agricultural pollutants and climate change.58 Additional impacts on the industry are likely to arise from socio-economic factors, such as changes in labor costs (given the labor-intensive nature of production), socio-economic and political factors (e.g., competition for land resources, R&D initiatives, industry support and development), and future demand patterns for sugarcane.
Adaptation Studies
A second set of studies focuses on the adaptation of sugarcane production to climate change (i.e., responses undertaken to adjust to the observed and/or projected impacts of climate change), but there is limited evidence regarding successful adaptation outcomes. Nine studies located for this review offer conceptual overviews of different adaptation options or reviews of other studies, while eight studies offer empirical insights into adaptation practices (Table 3). Among the conceptual studies are Zhao and Li2 who propose breeding programs, planting drought tolerant varieties, improving management practices, and adapting irrigation
and drainage. Chandiposha argues for the introduction of drought resistant varieties, irrigation, and drainage to cope with flooding. Srivastava and Rai120 recommend several agronomic measures, including field preparation, planting patterns, and weed, pest, and disease management, as well as soil, nutrient, and irrigation management and biotechnological approaches. Goebel and Sallam121 make a case for adopting ecology-based pest management. In the Australian context, Park and colleagues11, 32, 38, 43, 44 recommend (a) improved management of limited water supplies (e.g., new irrigation technologies, more efficient use of water supplies, better water capture and storage), (b) technological solutions based on engineering design principles and computer-aided modelling (e.g., improved crop varieties, better machinery technologies), (c) improved management strategies (e.g., better farm-scale planning and design, more flexible agronomic management by adjusting planting dates), (d) enhanced decision-making tools (e.g., enhanced climate and weather forecasting, irrigation scheduling, fertilizer management), and (e) institutional measures (e.g., improving national and regional climate adaptation plans, relocating sugarcane production areas, and diversifying into alternative income options for rural enterprises).
The empirical studies are geographically dispersed and present evidence from Mexico, Egypt, Brazil, Australia, and South Africa. In Mexico, a survey conducted in the Central Gulf region shows that 32.2% of sugarcane growers are taking measures to adapt to climate change, including waiting for seasonal rains for production and irrigation purposes, using spray irrigation, and conducting risk assessments when constructing irrigation systems.122 Other empirical studies focus on the development of more efficient water use strategies for Egypt,123 irrigation strategies for South Africa and Brazil,72, 124 and drought tolerance traits for Australian sugarcane.125 In the context of Mauritius, Cheeroo-Nayamuth and Nayamuth34 conclude that even though irrigation appears to be the best adaptation solution, it is difficult to implement due to water availability, costs, and possible policy restrictions. The researchers therefore recommend considering possible changes in cultivars. A similar recommendation is put forward by Inman-Bamber et al.125 who assess traits to improve sugarcane for conditions that are expected to worsen under a changing climate, such as water stress in Australia.125
Despite a good conceptual knowledge of different adaptation measures, the existing evidence is not sufficient to provide recommendations regarding what adaptation options to implement, and it is evident that not all adaptation efforts are likely to be equally successful in practice. Many studies recommend changes in cultivars or breeding cultivars with improved drought-tolerance and water use efficiency traits. However, researchers point out that further work is needed to understand exactly how sugarcane plants will respond to increases in atmospheric CO2 (e.g., in terms of photosynthesis or biomass accumulation) as well as other climate change impacts (e.g., water stress), before we attempt to optimize their physiological traits.33 In addition, not all adaptation measures will work equally well in different environments. Deressa et al.72 find that climate change has a significant nonlinear impact on net revenue per hectare in South Africa, with a higher sensitivity to increases in air temperature than precipitation. The authors therefore conclude that irrigation will not be an effective adaptation measure, and recommend other technological or management solutions (e.g., planting different sugarcane varieties).
There is limited empirical evidence of the uptake, cost, benefits, and effectiveness of different adaptation measures (as well as the risk of maladaptation) in different countries and regions, and for different actors along the sugar value chain (e.g., farmers, mills, distributors). For example, not much is known about the coping range of sugarcane producers in different areas; that is, their ability to accommodate variability in climatic conditions without experiencing adverse consequences.126 Studies also provide very limited insights into the decision-making criteria for selecting among adaptation options; how the selected adaptation option(s) should be monitored, evaluated, and reviewed; and the possible challenges or trade-offs that should be considered (e.g., adaptation might not just occur in response to environmental considerations, but also in response to changes in demand). There are currently few studies that examine how possible changes in the number and/or severity of extreme weather events might impact the sugarcane industry, even though the sugar price has been significantly impacted in recent years not just by political and economic factors, but also by supply shortfalls due to weather disruptions (see Background section),23 In order to make the best policy decisions on climate response strategies, it is important to understand how
different sectors overlap (e.g., the sugarcane industry and the water sector). It appears that adaptation to climate change will be particularly important for sugarcane production in developing countries due to low adaptive capacity, vulnerability to hazards, and poor forecasting and planning systems,2 but there are few studies focusing on both climate impacts (see above) and adaptation in these contexts.
Table 2: Adaptation Studies
Reference Focus of the Analysis Approach Location Key Findings
Conceptual studies
Sengar et al.
(2015)33 Impact of climate change on sugarcane productivity Conceptual India Discusses the need to further understand and detail physiological traits before designing a strategy to optimize sugarcane improvement Zhao and Li (2015)2 Review of climate change impacts on
sugarcane and strategies to improve adaptive capacity
Conceptual Not specific to any
location Suggests a number of adaptation strategies, including breeding programs, planting drought tolerant varieties, irrigation and drainage systems, as well as improved management practices
Bhaskaran and Nair
(2015)128 Review of climate impacts and adaptation options Conceptual Not specific to any location Suggests a number of adaptation strategies, including breeding of sugarcane varieties to cope with climate change Srivastava and Rai
(2012)120 Impacts of climate change on sugarcane
production and adaptation options Conceptual Not specific to any location Discusses a range of agronomic measures, including field preparation, planting patterns, weed, pest and disease management, as well as soil, nutrient, and irrigation management, and biotechnological approaches
Goebel and Sallam
(2011)121 Analysis of how new threats (global travel, world trade, change in climate conditions) increase risks from pests and diseases in sugarcane
Conceptual Various - Australia, Brazil, South Africa, Reunion Island
Makes a case for the adoption of pest management and the uptake of ecology-based pest management to adapt to threats
Park et al. (2010)32 Impact of climate change on the Australian
sugar industry and adaptation options Conceptual Australia The greatest direct climate change impact for Australian sugarcane production is likely the projected change in the amount, frequency, and intensity of future rainfall
Reviews
Chandiposha
(2013)70 Impact of climate change on sugarcane and adaptation strategies Review Zimbabwe Increases in air temperature may lead to increased cane growth during winter, but may also increase irrigation needs and affect the prevalence of weeds and pests. Adaptation options include drought resistant varieties, irrigation, and drainage to cope with flooding. Park (2008)10
Impact of climate change on the Australian
sugar industry and capacities for adaptation Review Australia The most effective way to assess the impacts of climate change is to conduct climate assessments in collaboration with stakeholders Park and Attard
(2005)40 Impact of climate change on the Queensland sugar industry and capacities for adaptation Review Queensland The net effects of climate changes impacts are unknown and may vary between regions; a whole-of-industry impact/adaptation plan should therefore be developed
Empirical studies
Guerrero-Carrera et
al. (2015)122 Grower perceptions of climate change impacts on sugarcane crops and the adaptation actions they are implementing
Survey Mexico 32.2% of growers to take some adaptive action (in particular related to irrigation)
Hamada (2014)123 Impact of drought and the effectiveness of
adaptation measures Linear Programming Model
Egypt Examines the potential for more efficient water use throughout Egypt based on institutional changes
(2014)124 saving irrigation strategy Inman-Bamber, et
al. (2012)125 Potential benefits of a number of traits for drought tolerance Crop modelling (APSIM) Australia Suggests that increased rooting depth, increased intrinsic water use efficiency, and reduced conductance lead to increased transpiration efficiency as best traits in water-limited environments
Park et al. (2007)10
Impact of climate change on the sugar value
chain in Australia Qualitative and quantitative assessment
Rocky Point, Mossman
(Aust) Yield potential will increase marginally if planting occurs earlier in the south, while a delay in planting in the north may increase productivity by 2030 Deressa et al.
(2005)72 Impact of climate change on sugarcane production under irrigation and dryland conditions
Ricardian model South Africa Climate change has a significant nonlinear impact on net revenue per hectare with a higher sensitivity to increases in air temperature than precipitation. Irrigation is not an effective adaptation measure.
Cheeroo-Nayamuth and Nayamuth (2001)34
Climate change impacts on sugarcane yield in
Mauritius and adaptation options Crop modelling (APSIM) Mauritius Sugarcane yields will be reduced due to lower water use efficiencies and higher respiratory demands under various climate change scenarios. Even though irrigation appears to be the best adaptation solution, it is difficult to implement due to water availability, costs, and possible policy restrictions
Nayamuth (2005)36 Climate change impacts on sugarcane yield in
Mauritius and adaptation options Analysis of long-term data Mauritius Adaptation options include improvement to water storage/availability as well as shifts in sugarcane areas towards the poles and higher altitudes; changes have implications for milling, industry profitability, and national policy
Mitigation Studies
There is also a stream of research (20 studies) concerned with mitigating the energy use and GHG emissions resulting from sugarcane production. Mitigation can be understood as a response to the challenge of reducing GHG emissions (with the idea that aggregate mitigation efforts in the agricultural sector may help to limit the extent of future climate change). The aim of the mitigation studies is to assess on-farm management and harvesting practices that could reduce energy use and GHG emissions, and to outline how to lower the impact of sugarcane production on climate change. Topics covered include work on understanding on-farm emissions and energy use,129 the role of sugarcane fields as sources or sinks for GHGs,130 and the GHG emissions reduction potential associated with shifting to green harvest and mechanized farm practices.131, 132 In addition, some studies seek to map out energy use and GHG emissions that occur along the entire sugarcane value chain and offer so-called lifecycle and carbon footprint assessments.133, 134 Most studies on the practice of burning sugarcane fields focus on Brazil, where burning has been a traditional harvest method. Other studies outside the scope of this review focus on the topic of burned harvest without explicit links to climate change,135 and we acknowledge the wider body of research on these topics. Taken together, mitigation studies address environmental risk management from the point of GHG emissions and pollutant release mitigation,136 and investigate how sugarcane production can limit environmental impacts. The potential for emission reduction opportunities has also prompted researchers to evaluate carbon market opportunities for the sugarcane industry.137
Within a broader societal context (and beyond the scope of a detailed review here), the mitigation potential associated with societal shifts to biofuels (including sugarcane ethanol) has received much research attention. The shift to biofuels has led to significant debates among international organizations, policy-makers, community leaders, and researchers regarding the impacts of biofuel use. These impacts are due to increasing farmland requirements22, 138 and have consequences for food production, food security, and food prices.27 There is controversy regarding the extent to which biofuels are a cleaner energy source, given their full lifecycle impacts (as compared to other biofuels and renewable energy
options). However, from an adaptation perspective, the question arises whether producers are better placed to focus on raw sugar production, or if they should diversify and expand into biofuel production. Many of these debates are ongoing and present significant research and development opportunities, in particular for locating research within a broader climate response framework that considers a link between climate mitigation and adaptation practices (see next section).17
Table 3: Mitigation Studies
Reference Focus of the Analysis Approach Location Key Findings
Australia
Baillie and Chen
(2012)129 Mitigation of on-farm GHG emissions and energy use Study of direct on-farm energy use Australia Potential savings in average energy costs of $30 to $100/ha are practically achievable Weier (1998)130 Investigates the role of sugarcane fields as sources or sinks
for GHG emissions Review Australia This review suggests changes in management procedures to reduce Nemissions 2O
Brazil
Bordonal et al.
(2013)131 GHG emission reductions due to the change from burned
harvest to green harvest IPCC methodology for estimating GHG emissions
São Paulo (Brazil) Suggests that green harvest with crop rotation and reduced tillage could result in a mitigation potential of 70.9 Mt CO2eq up to 2050
Bordonal et al.
(2013)132 GHG emission reductions due to the change from burned harvest to green harvest and changes in management practices
IPCC methodology for estimating GHG emissions
Southern Brazil Suggests that changes to management practices (green harvest, tillage, crop rotation strategies) can contribute considerably to achieving Brazil’s GHG reduction goals
Capaz et al.
(2012)140 GHG emission reductions due to mechanisation and a reduction in burned harvest IPCC methodology for estimating GHG emissions
São Paulo (Brazil) A reduction in burning and the introduction of mechanical harvesting have reduced GHG emissions
França et al.
(2012)141 Determination of emission factors for sugarcane burning Experiment Brazil Provides findings for emission factors to generate more realistic emission scenarios De Figueiredo
and La Scala (2011)142
GHG emission reductions due to the change from burned
harvest to green harvest IPCC methodology for estimating GHG emissions
Brazil A conversion from burned to green harvest could save up to 1484.0 kg CO2equiv. ha−1 y−1 (including soil carbon sequestration)
Seabra et al.
(2011)134 Life cycle assessment (LCA) of sugarcane products to
determine GHG emissions and energy use LCA using a range of data sources Brazil (Center -South Region) Estimates that GHG emissions are 234 g CO 2eq/kg Arraes et al.
(2010)143 GHG not emitted due to mechanical harvesting of sugarcane IPCC methodology, satellite imagery Northwestern São Paulo Finds a significant increase of mechanical harvesting in the study area and a corresponding GHG reduction of more than 300,000 t yr-1 Cerri et
al.(2007)144 GHG emissions associated with sugarcane production and burning versus non-burning harvesting Modelling Brazil Suggests that 0.2 Mt COatmosphere annually when non-burning is adopted in Brazil 2-equivalent (0.05 Mt C) are not emitted into the
Other regions
Sefeedpari et al.
(2014)145 Energy use and CO2 emissions by sugarcane farms Survey Iran (involves one company) Reports on input-output energy use pattern for the sugarcane production process Acreche et al.
Rein (2011)147
Determining the carbon footprint for sugar production Develops estimation
procedure N/A The carbon footprint is primarily affected by sugarcane yield, sugar recovery, fertilizer usage, irrigation, cane burning and power export Yuttitham et al.
(2011)133 Carbon footprint of sugarcane production Field surveys, questionnaires and interviews -
Eastern Thailand Concludes that sugar production has a carbon footprint of 0.55 kg CO2e kg−1 sugar (includes sugarcane production and milling)
Magalhaes
(2010)148 Analysis of the environmental impact and energy efficiency of sugarcane processing technologies Comparison of different technologies N/A Outlines opportunities for energy savings based on the use of different technologies Mashoko et al.
(2010)149 Environmental impacts associated with sugarcane production Life cycle analysis South Africa Results show that non-renewable energy consumption is 5350 MJ per tonne of raw sugar produced (40% of which is from fertilizer and herbicide manufacture)
Rein (2010)150
Determining the carbon footprint for sugar production (raw
and refined cane sugar) Identifies aspects of production affecting GHG emissions
N/A Outlines options for reducing carbon footprint in refining (energy efficiency, choice of energy source)
Fukushima and
Chen (2009)151 GHG emission reductions in sugarcane cultivation Life-cycle assessment (LCA) using a range of data sources
Taiwan Finds that net GHG emissions associated with sugarcane production are about −280 kg-CO2-equiv. per ton of raw sugarcane, suggests modifications of the analysis for other regions
Ramjeawon
(2004) 152 Lifecycle assessment (LCA) of sugarcane production Data from companies, factories, sugar statistics, databases, literature
Mauritius Concludes that fossil fuel energy use leads to 160 kg of CO2 per tonne of sugar
McNish et al.
