Expected global suitability of coffee, cashew and avocado due to climate change

RESEARCH ARTICLE Expected global suitability of coffee, cashew and avocado due to climate change Roman Gru¨ terID*, Tim Trachsel, Patrick Laube, Isabel Jaisli Institute of Natural Resource Sciences, Zurich University of Applied Sciences, Wa¨ denswil, Switzerland * roman.grueter@zhaw.ch Abstract Coffee, cashew and avocado are of high socio-economic importance in many tropical small- holder farming systems around the globe. As plantation crops with a long lifespan, their culti- vation requires long-term planning. The evaluation of climate change impacts on their biophysical suitability is therefore essential for developing adaptation measures and select- ing appropriate varieties or crops. In this study, we modelled the current and future suitability of coffee arabica, cashew and avocado on a global scale based on climatic and soil require- ments of the three crops. We used climate outputs of 14 global circulation models based on three emission scenarios to model the future (2050) climate change impacts on the crops both globally and in the main producing countries. For all three crops, climatic factors, mainly long dry seasons, mean temperatures (high and low), low minimum temperatures and annual precipitation (high and low), were more restrictive for the global extent of suitable growing regions than land and soil parameters, which were primarily low soil pH, unfavour- able soil texture and steep slopes. We found shifts in suitable growing regions due to climate change with both regions of future expansion and contraction for all crops investigated. Cof-

fee proved to be most vulnerable, with negative climate impacts dominating in all main pro- ducing regions. For both cashew and avocado, areas suitable for cultivation are expected to expand globally while in most main producing countries, the areas of highest suitability may decrease. The study reveals that climate change adaptation will be necessary in most major producing regions of all three crops. At high latitudes and high altitudes, however, they may all profit from increasing minimum temperatures. The study presents the first global assess- ment of climate change impacts on cashew and avocado suitability. Introduction Plantation crops such as coffee, cashew and avocado are among the most important cash crops and contribute substantially to the livelihoods of smallholder farmers around the world. These crops have a lifespan of several decades and therefore long-term agricultural planning consid- ering the expected impacts of climate change is especially important. Global warming of 1.2 up to 3.0˚C by 2050 is estimated by the Intergovernmental Panel on Climate Change depending on different greenhouse gas emission pathways [1]. Such changes in temperature will directly PLOS ONE PLOS ONE | https://doi.org/10.1371/journal.pone.0261976 January 26, 2022 1 / 24 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Gru¨ter R, Trachsel T, Laube P, Jaisli I (2022) Expected global suitability of coffee, cashew and avocado due to climate change. PLoS ONE 17(1): e0261976. https://doi.org/10.1371/journal. pone.0261976

Editor: Abel Chemura, Potsdam Institute for Climate Impact Research, GERMANY Received: April 22, 2021 Accepted: December 14, 2021 Published: January 26, 2022 Peer Review History: PLOS recognizes the benefits of transparency in the peer review process; therefore, we enable the publication of all of the content of peer review and author responses alongside final, published articles. The editorial history of this article is available here: https://doi.org/10.1371/journal.pone.0261976 Copyright: © 2022 Gru¨ter et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All resulting suitability maps are available from the Figshare repository (DOI: 10.6084/m9.figshare.17702459). Funding: This study has been funded by the Syngenta Foundation for Sustainable Agriculture.

assessment of current and future distributions across the Americas was made by Ramı´rez-Gil et al. [18], including some of the major producing countries. They identified both regions of future expansion and contraction. To our knowledge, only two studies investigated avocado suitability outside these continents [19, 20]. Global biophysical modelling of current and future suitability of coffee, cashew and avocado is therefore essential to take informed decisions in long-term agricultural planning with the aim of maintaining farmers’ livelihoods and of foster- ing the sustainable use of natural resources. The objective of this paper is to estimate current and future biophysical suitability for coffee arabica, cashew and avocado production on a global scale and to identify and discuss global and regional trends. We modelled crop suitability based on their biophysical requirements. For the first time, both land and soil (artificial surfaces, protected areas, soil texture, coarse fragments, pH, organic carbon content, salinity) and climate (temperature, precipitation, humidity) parameters were taken into account on a global scale. Climate change projections were based on 14 global circulation models (GCMs) and three representative concentration pathways (RCP 2.6, 4.5 and 8.5) for the year 2050. We investigated climate change impacts (relative decreases and increases in crop suitability) both globally and in the main producing countries of the three plantation crops. Materials and methods The GIS-based decision support system CONSUS [21] was used to model the biophysical suit-

ability of coffee (Coffea arabica L.), cashew (Anacardium occidentale L.) and avocado (Persea americana Mill.). The model is based on multi criteria evaluation of biophysical variables and was applied on a global scale for current and future climatic conditions. The land suitability evaluation in CONSUS consists of four steps [21]: niche description, site description, matching and aggregation. In the niche description, the biophysical crop requirements (climate, land and soil parameters such as temperature, precipitation or soil pH) are first identified based on literature search. Then, each parameter is classified into four suitability classes (see Table 1) following the FAO land evaluation approach [22]: S1 (highly suitable), S2 (moderately suit- able), S3 (marginally suitable), N (unsuitable). For coffee for example, a soil pH between 4.5 and 5.0 is classified as marginally suitable (Table 1). For the site description, spatial data corre- sponding to the crop-specific requirements is identified. In this study, publicly available global raster datasets with a resolution of 30 arc seconds were used (see Table 2). The matching of the PLOS ONE Global suitability of coffee, cashew and avocado PLOS ONE | https://doi.org/10.1371/journal.pone.0261976 January 26, 2022 2 / 24 The funders supported the research team in the selection of the modelled crops. Apart from that they had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist.

Table 1. Biophysical requirements of coffee ( Coffea arabica L.), cashew ( Anacadrium occidentale L.) and avocado ( Persea americana Mill.) used in the model, classified into four suitability classes (S1: Highly suitable, S2: Moderately suitable, S3: Marginally suitable, N: Unsuitable). The classification was done based on several sources for coffee [24–28], cashew [13, 16, 24, 25]and avo- cado [24, 25, 29, 30]. Coffee Cashew Avocado Criteria S1 S2 S3 N S1 S2 S3 N S1 S2 S3 N Climate Mean annual temperature (˚C) 17–22 22–25 15–17 25–28 12–15 >28 <12 24–28 28–31 20–24 31–34 15–20 >34 <15 18–26 26–30 15–18 30–45 10–15 >45 <10 Mean minimum temperature of coldest month (˚C) 10–19 19–21 7–10 21–23 4–7 >23 <4 >10 8–10 4–8 <4 >16 13–16 8–13 <8 Mean annual precipitation (mm) 1400–1800 1800– 2300 1000– 1400 2300– 4200 750– 1000 >4200 <750 1000–2250 2250– 3200 800– 1000 3200– 4500 500– 800 >4500 <500 1200–1800 1800– 2000 1200– 1000 2000– 2500 750– 1000 >2500 <750 Length of dry season (months) 1–4 4–5 0–1 5–6 - >6 0–4 4–5 5–6 >6 1–4 4–6 <1 >6 - Mean relative humidity of driest month (%) 40–70 70–80 30–40 80–90 20–30 >90 <20 >30 25–30 20–25 <20 - - - - Land and Soil Artificial surfaces (type) a 0,2,3,4,5,6,7,8,9,10,11 - - 1 0,2,3,4,5,6,7,8,9,10,11 - - 1 0,2,3,4,5,6,7,8,9,10,11 - - 1 Protected areas (category) b - - - 1,2,3,4,5,6,7,8,9,10 - - - 1,2,3,4,5,6,7,8,9,10 - - - 1,2,3,4,5,6,7,8,9,10 Slope (%) 0–8 8–16 16–30 >30 0–8 8–16 16–30 >30 0–8 8–16 16–30 >30 Soil texture (USDA class) c 1,3,4,5,7,8,10 6 9 2,11,12

1,2,3,4,5,6,7,8,9,10,11 - 12 - 4,5,6,7,8,9,10,11,12 2,3 1 - Coarse fragments (vol%) 0–15 15–35 35–55 >55 0–15 15–35 35–55 >55 0–15 15–35 35–55 >55 Soil organic carbon (%) >1.2 0.8–1.2 <0.8 - >0.8 0.5–0.8 0.1–0.5 <0.1 >1.2 0.8–1.2 <0.8 - Soil pH 5.5–6.5 6.5–7.0 5.0–5.5 7.0–7.5 4.5–5.0 >7.5 <4.5 5.2–7.0 7.0–7.5 4.8–5.2 7.5–8.0 4.5–4.8 >8.0 <4.5 5–6.5 6.5–7.5 4.5–5 7.5–8.3 4.3–4.5 >8.3 <4.3 Soil salinity (ECe) 0–0.5 0.5–1.5 1.5–2.5 >2.5 0–2 2–3 3–4 >4 0–3 3–4 4–5 >5 aArtificial surfaces were classified according to FAO global land cover SHARE ([31]; 1 = artificial surfaces, 2 = cropland, 3 = grassland, 4 = tree covered areas, 5 = shrubs covered areas, 6 = herbaceous vegetation, aquatic or regularly flooded, 7 = mangroves, 8 = sparse vegetation, 9 = bare soil, 10 = snow and glaciers, 11 = water bodies). bProtected areas were classified according to the IUCN management categories ([32]; 1 = Ia, 2 = Ib, 3 = II, 4 = III, 5 = IV, 6 = V, 7 = VI, 8 = not reported, 9 = not applicable, 10 = not assigned). cSoil texture was classified according to USDA soil taxonomy (1 = clay, 2 = silty clay, 3 = sandy clay, 4 = clay loam, 5 = silty clay loam, 6 = sandy clay loam, 7 = loam, 8 = silty loam, 9 = sandy loam, 10 = silt, 11 = loamy sand, 12 = sand). https://doi.org/10.1371/journal.pone.0261976.t001 PLOS ONE Global suitability of coffee, cashew and avocado PLOS ONE | https://doi.org/10.1371/journal.pone.0261976 January 26, 2022 3 / 24

crop requirements with the spatial data is done for every parameter individually (e.g. soil pH). During this process, each raster cell of the corresponding dataset is reclassified into one of the four suitability values. In the case of coffee, for example, a soil pH of 4.7 (Table 1) of a certain land unit is classified as marginally suitable (S3). This matching of crop requirements with spa- tial data results in separate suitability maps for each parameter investigated, for example the soil pH suitability map for coffee. The resulting maps are aggregated by the maximum limiting factor [23], rating the suitability of each raster cell by the factor with the lowest value. If the suitability of all crop requirements other than soil pH in the above-mentioned example were Table 2. Data sources used for the modelling of the crops’ climate, land and soil suitability [31–38]. All datasets are in a raster format and have a resolution of 30 arc seconds. Criteria Data source URL Reference Climate Mean annual temperature (˚C), current (1970–2000) and future (2041–2060) WorldClim: Global climate and weather data, version 2.0 (BIO 1) www.worldclim.org [33] Mean minimum temperature of coldest month (˚C), current (1970–2000) and future (2041– 2060) WorldClim: Global climate and weather data, version 2.0 (BIO 6) www.worldclim.org [33] Mean annual precipiataion (mm), current (1970–2000) and future (2041–2060) WorldClim: Global climate and weather data, version 2.0 (BIO 12) www.worldclim.org [33] Length of dry season (months) WorldClim: Global climate and weather data, version 2.0

(monthly precipitation) Global aridity and PET database (potential evapotranspiration) www.worldclim.orgcgiarcsi. community/data/global-aridity- and-pet-database [33,37,38] Mean relative humidity of dryest month (%) CliMond: Global climatologies for bioclimatic modelling (relative humidity at 9 am) www.climond.org/ClimateData. aspx [36] Land and Soil Artificial surfaces (type) FAO Global Land Cover (GLC-SHARE) Beta-Release 1.0 Database www.fao.org/geonetwork/ [31] Protected areas (category) The World Databae on Protected Areas (WDPA) www.protectedplanet.net [32] Slope (%) Derived from ESRI Terrain Service Soil texture (USDA class) SoilGrids—global griddes soil information (soil texture at 15 cm depth) www.isric.org/explore/soilgrids [35] Coarse fragments (vol%) SoilGrids—global griddes soil information (coarse fragments at 15 cm depth) www.isric.org/explore/soilgrids [35] Soil organic carbon (%) SoilGrids—global griddes soil information (soil organic carbon at 15 cm depth) www.isric.org/explore/soilgrids [35] Soil pH SoilGrids—global griddes soil information (soil pH at 15 cm depth) www.isric.org/explore/soilgrids [35] Soil salinity (ECe) Harmonized Soil Database, version 1.2 www.fao.org/soils-portal/data- hub/soil-maps-and-databases/ harmonized-world-soil-database- v12/ [34] https://doi.org/10.1371/journal.pone.0261976.t002 PLOS ONE Global suitability of coffee, cashew and avocado PLOS ONE | https://doi.org/10.1371/journal.pone.0261976 January 26, 2022 4 / 24

rated as S3 or higher, the overall suitability would therefore be S3. The resulting global maps show the potential land suitability of the studied crop under rainfed conditions, without taking into account agricultural management options such as liming or irrigation. The results are based on growth factors that are sufficiently described for the respective crop and where corre- sponding global spatial datasets are available. Suitability evaluations were undertaken for cur- rent and predicted future climatic conditions. Current suitability modelling For the modelling of the current global land suitability for the three plantation crops, their bio- physical requirements were identified via a literature search. Table 1 lists their climatic, land and soil requirements that were used in the model, classified into the four suitability classes. This classification was done based on Sys et al. [24] taking into account additional scientific lit- erature (see Table 1). Whenever several authors defined different thresholds between suitabil- ity classes of a criterion, the threshold was set conservatively resulting in a higher crop suitability or it was set in agreement with the majority of indications. Global climate and land/ soil raster data with a spatial resolution of 30 arc seconds were used from established global cli- mate models and satellite-data based global land use datasets and are listed in Table 2. Artificial surfaces according to the FAO Global Land Cover SHARE dataset [31] and protected areas

based on the World Database on Protected Areas [32] were rated as ‘unsuitable’ (see Table 1). The length of the dry season was based on the monthly precipitation (P) and the potential evapotranspiration (PET), and was calculated as the number of months where P < ½ PET [24]. Coffee, cashew and avocado have similar ecological niches (Table 1). However, there are still important differences in their biophysical requirements. While avocado has the highest suitable temperature range, coffee is most susceptible to high temperatures. At the same time, avocado is more susceptible to low temperatures than the other crops during the coldest month. With regard to precipitation, cashew has the highest suitable range, tolerating both higher and lower values than coffee and avocado. Avocado is most susceptible to high precipi- tation, but more tolerant to longer dry seasons. Both avocado and coffee have a slightly reduced suitability in regions without a dry season. When looking at edaphic factors, coffee has a narrower ecological niche than the other crops. Compared to coffee, both cashew and avocado are more tolerant to high and low soil pH and less restricted regarding soil texture. Combining all these factors, cashew has the broadest ecological niche, followed by avocado and coffee. For each criterion listed in Table 1, the crop suitability was calculated globally. The results for all five climate requirements and for the eight land and soil requirements were then aggre- gated by the lowest suitability value to obtain the overall climate suitability and land and soil

suitability, respectively [22]. Finally, the climate and the land and soil suitability were com- bined once again by the lower rate, resulting in the overall current suitability. For the identifi- cation and discussion of most limiting factors in the different regions, the individual suitability maps for the different requirements were compared. All analyses were done using the ESRI ArcGIS Pro software version 2.5.0. Future suitability modelling To estimate the potential effects of climate change on future suitability, the impacts were mod- elled based on three representative concentration pathways (RCPs; [39]) for the future climatic conditions of 2050 (average of projected climate from 2041–2060). Downscaled CMIP5 data [40] of 14 global climate models (GCMs: BBC-CSM1-1, CCSM4, CNRM-CM5, GFDL-CM3, PLOS ONE Global suitability of coffee, cashew and avocado PLOS ONE | https://doi.org/10.1371/journal.pone.0261976 January 26, 2022 5 / 24

GISS-E2-R, HadGEM2-AO, HadGEM2-ES, IPSL-CM5A-LR, MIROC-ESM-CHEM, MIRO- C-ESM, MIROC5, MPI-ESM-LR, MRI-CGCM3 and NorESM1-M) were used for RCP 2.6 (low emissions), 4.5 (intermediate emissions) and 8.5 (high emissions), available in 30 arc sec- ond resolution in WorldClim version 2.0 (www.worldclim.org). Three relevant bioclimatic variables (BIO 1, 6 and 12) were retrieved from the data of all 14 GCMs by calculating means (see Table 2). These three variables were used for the modelling of future crop suitability in this study. All other parameters listed in Table 1 were kept constant. The overall future climate suitability was then calculated using the future projections of the three bioclimatic variables described above. For the overall future suitability, the climate and the land and soil suitability were aggregated again by the maximum limiting factor. All the calculations were done for RCP 2.6, 4.5 and 8.5 separately, using the ESRI ArcGIS Pro software version 2.5.0. Calculation of expected changes To visualize the projected overall suitability change between 2000 and 2050, the difference between the overall suitability of 2000 and 2050 was calculated for each raster cell. The result- ing values between -3 and +3 indicate by how many suitability classes the different regions are expected to decrease or increase (e.g. a value of -2 indicating a negative change from S1 highly suitable to S3 moderately suitable). Additionally, the changes in suitability by 2050 for the three different RCPs were calculated

individually for each crop for the four main producing countries. The main producing coun- tries were identified using FAOSTAT (www.fao.org/faostat) data concerning the quantity pro- duced in 2018. For coffee, these are Brazil, Vietnam, Indonesia and Colombia with a share of 64% of the global production. For cashew, Vietnam, India, Coˆte d’Ivoire and Benin (Benin was chosen instead of the Philippines because of very similar quantities produced but a much big- ger area harvested in 2018) were identified, representing 73% of the global production. Finally, the main avocado producing countries are Mexico, the Dominican Republic, Peru and Indo- nesia, accounting for 58% of the global production. For these countries, the changes in suitable areas were calculated based on the area per suitability class that was calculated after equivalent projection to the Equal Earth coordinate system in ESRI ArcGIS Pro version 2.5.0. Results An overview of the results relevant for coffee, cashew and avocado is first presented. Subse- quently, the current and future suitability and the expected changes are described individually for each of the three crops. Factors determining suitability The modelled suitable areas of all three plantation crops show a similar global extent due to their similar biophysical requirements (Figs 1–3). Globally, cashew has the largest suitable growing areas globally, followed by avocado and coffee (see Tables 3–5). However, as far as the most limiting factors and the extent of highly (S1) and moderately (S2) suitable areas are con-

cerned, there are important differences between the crops. For all three, the modelled climate suitability is more restrictive than the land and soil suitability for the global growing regions. All climatic factors used in the models (see Table 1) are important suitability limiting factors in several regions, except for the relative humidity of the driest month. For coffee, humidity is a co-limiting factor in very few areas in Central Africa and Southeast Asia, while it is no requirement in the avocado model and does not limit cashew suitability at all. Overall, four of the biophysical land and soil requirements (artificial surfaces, protected areas, slope and coarse fragments) are not crop-specific, and therefore the suitability maps for PLOS ONE Global suitability of coffee, cashew and avocado PLOS ONE | https://doi.org/10.1371/journal.pone.0261976 January 26, 2022 6 / 24

these parameters are identical for all three crops (see Table 1). However, whether these param- eters are limiting factors in the overall suitability still differs between the three crops depending on their other biophysical requirements. The artificial areas that are classified as not suitable (N) are concentrated around the global metropolises and represent only a minor share of the global suitable areas. In contrast, the protected areas, also rated as N, represent a substantial share in all growing regions with a global terrestrial coverage of about 15% [41]. For all three crops, the slope criterion restricts agricultural suitability where it is above 16% (S3) and above 30% (N), both of which obviously represent mountainous and hilly regions such as the Hima- layas or the Andes, but also smaller-scale mountain chains across all growing regions. The coarse fragments of the soil hardly have any effect on crop suitability in any growing region. Additionally, both soil salinity and organic carbon content are not relevant criteria for the suit- ability of coffee, cashew and avocado and will therefore not be described further below. Current coffee suitability Globally, the highest overall current coffee suitability (S1 & S2) is found in Central and South America (esp. Brazil), in Central and West Africa, and in parts of South and Southeast Asia (Fig 1). The northern and southern extents of the global growing regions are restricted by cli- mate factors, mainly by three parameters: long dry seasons (northern and southern boundaries

of the growing regions in Africa, India, Australia, Eastern Brazil), high mean annual tempera- tures (West Africa, certain Southeast Asia regions, Central America) and low mean minimum temperatures of the coldest month (northern and southern boundaries in America, China, cer- tain Southeast Asia regions, some mountainous areas). In some of the climatically suitable regions, the land and soil criteria greatly restrict the suitability of coffee cultivation. Low soil Fig 1. Overall current suitability for coffee (aggregated climate, land and soil suitability). A Central and South America, B West and Central Africa, C South and Southeast Asia. https://doi.org/10.1371/journal.pone.0261976.g001 PLOS ONE Global suitability of coffee, cashew and avocado PLOS ONE | https://doi.org/10.1371/journal.pone.0261976 January 26, 2022 7 / 24

pH limits coffee suitability in South America (Amazon basin), Central Africa (Congo basin) and Southeast Asia (Sumatra, Malaysia, Borneo, New Guinea). In few regions, unsuitable soil texture (e.g. Florida) or steep slopes (e.g. North India) are the limiting factors. The main coffee producing countries investigated (Brazil, Vietnam, Indonesia, Colombia) have very diverse agroclimatic conditions. Therefore, different climatic requirements (annual temperature, annual precipitation, length of dry season and minimum temperature of coldest month) are important limiting factors determining current coffee suitability (Table 3) depend- ing on the region. For example, in Central and Southern Vietnam (see Fig 4), high annual tem- peratures limit current suitability, while in the South (too high) and in the northern mountains (too low) the limiting factor is the minimum temperatures of the coldest month, and in Central and Northeast Vietnam the high annual precipitation. Future coffee suitability Taking into account climate change scenarios (Table 3 and Fig 5), the suitability of coffee will drastically decrease by 2050. The highest suitability (S1) will decrease by more than 50% in all three RCPs and the moderately suitable (S2) regions decrease by 31% (RCP 2.6) to 41% (RCP Table 3. Suitable coffee growing areas globally and in main producing countries (S1: highly suitable, S2: Moder- ately suitable, S3: Marginally suitable, N: Unsuitable) for current (2000) and future (2050) conditions under three

RCPs: 2.6 (low emissions), 4.5 (intermediate emissions), 8.5 (high emissions). Expected changes in suitable areas are given as a percentage. RCP 2.6 RCP 4.5 RCP 8.5 Suit Class 2000 (km2) 2050 (km2) Δ (%) 2050 (km2) Δ (%) 2050 (km2) Δ (%) World total S1 36,240 16,540 –54.4 16,777 –53.7 14,678 –59.5 S2 5,709,608 3,951,207 –30.8 3,679,863 –35.5 3,369,550 –41.0 S3 14,709,645 15,118,407 2.8 13,995,976 –4.9 12,787,405 –13.1 N 104,044,240 105,413,581 1.3 106,807,118 2.7 108,328,100 4.1 Brazil S1 5,934 1,421 –76.1 1,268 –78.6 161 –97.3 S2 1,822,032 1,311,548 –28.0 1,161,921 –36.2 1,040,958 –42.9 S3 2,430,089 2,536,454 4.4 2,427,693 –0.1 1,939,711 –20.2 N 4,099,828 4,508,459 10.0 4,767,001 16.3 5,377,052 31.2 Vietnam S1 683 358 –47.6 196 –71.3 99 –85.5 S2 141,637 106,814 –24.6 89859 –36.6 75,422 –46.7 S3 108,773 143,838 32.2 146498 34.7 149,801 37.7 N 68,291 68,373 0.1 82829 21.3 94,060 37.7 Indonesia S1 0 0 0.0 0 0.0 0 0.0 S2 42,862 35,247 –17.8 26,828 –37.4 20,914 –51.2 S3 1,391,935 1,191,058 –14.4 922,242 –33.7 698,400 –49.8 N 387,893 596,385 53.7 873,620 125.2 1,103,376 184.5 Colombia S1 332 123 –63.0 108 –67.5 83 –75.0 S2 75,494 55,729 –26.2 50,886 –32.6 47,650 –36.9 S3 574,239 375,858 –34.5 273,066 –52.4 224,152 –61.0 N 473,101 691,455 46.2 799,106 68.9 851,282 79.9 https://doi.org/10.1371/journal.pone.0261976.t003 PLOS ONE Global suitability of coffee, cashew and avocado

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8.5). In the RCP 4.5 and 8.5, even marginally suitable (S3) locations will decrease by 5% and 13%, respectively, while areas not suitable for cultivation (N) will increase in all scenarios. Neg- ative changes in suitability will mainly be caused by increasing mean annual temperatures. Most current growing regions (Fig 5) are expected to decrease by at least one suitability class (Central and South America, Central and West Africa, India, Southeast Asia). Only a few regions, especially at the northern and southern borders of the growing areas, are expected to profit from climate change (e.g. Southern Brazil, Uruguay, Argentina, Chile, USA, East Africa, South Africa, China, India, New Zealand) due to increasing minimum temperatures of the coldest month. The main coffee producing countries investigated (Brazil, Vietnam, Indonesia, Colombia) are all seriously affected by climate change with a strong decline in suitable areas (S1:48–97% reduction; S2:18–51% reduction) and an increase in unsuitable areas by 2050 (Table 3). For example, increasing mean annual temperatures are mainly responsible for negative changes in suitability in Vietnam in all three emission scenarios (Fig 4). Current cashew suitability Globally (Fig 2), the regions manifesting highest levels of current cashew suitability (S1 & S2) are Central (e.g. Mexico) and South America (e.g. Brazil, Venezuela), the Caribbean islands (e.g. Cuba, the Dominican Republic), Central (e.g. the Democratic Republic of the Congo) and West Africa (e.g. Nigeria), Madagascar and South (e.g. Sri Lanka) and Southeast Asia (e.g.

Vietnam, the Philippines). The climate suitability is mainly limited by long dry seasons (e.g. India, northern boundaries in Africa, Brazil, Australia) and low mean annual temperatures (e.g. certain mountainous areas in South America and Southeast Asia). Additionally, the low Fig 2. Overall current suitability for cashew (aggregated climate, land and soil suitability). A Central and South America, B West and Central Africa, C South and Southeast Asia. https://doi.org/10.1371/journal.pone.0261976.g002 PLOS ONE Global suitability of coffee, cashew and avocado PLOS ONE | https://doi.org/10.1371/journal.pone.0261976 January 26, 2022 9 / 24

mean minimum temperatures of the coldest month limit the northern and southern bound- aries of some growing regions (e.g. China, USA, Brazil), and high annual precipitation limits suitability in some wet regions in Central and South America, West Africa, India and South- east Asia. For the land and soil requirements it is mainly low soil pH limiting cashew suitability in South America (Amazon basin), Central Africa (Congo basin) and Southeast Asia (e.g. Malaysia, Sumatra, Borneo). Soil texture is not relevant for the suitability of cashew. The suitability of cashew in the four major cashew producing countries investigated (Viet- nam, India, Coˆte d’Ivoire, Benin) are different due to diverse agroclimatic conditions prevail- ing in these countries (Table 4). For India as an example, current suitability of different climate parameters is shown in Fig 6. It is mainly limited by long dry seasons, low minimum temperatures of the coldest month and high annual precipitation. Future cashew suitability The future suitability models reveal that, depending on the growing region, both positive and negative changes in cashew suitability can be observed (Table 4 and Fig 7). In total, areas of high suitability (S1) increase by about 17% globally, and areas of moderate and marginal suita- blility (S2 and S3) by 2–13% (see Table 3). Unsuitable areas are expected to slightly decrease globally. The main regions of positive change (Fig 7) are the USA, South America (Brazil, Para- guay, Uruguay, Argentina), East Africa around Lake Victoria, South Africa, Angola, North

India, Vietnam, China and Australia. Primarily, rising minimum temperatures of the coldest month and in some regions (e.g. East Africa, Angola, Australia) rising annual temperatures are responsible for these positive changes in suitability. The main negative changes (Fig 7) are modelled to occur in Central and South America (Panama, Colombia, Venezuela), West Africa Fig 3. Overall current suitability for avocado (aggregated climate, land and soil suitability). A Central and South America, B West and Central Africa, C South and Southeast Asia. https://doi.org/10.1371/journal.pone.0261976.g003 PLOS ONE Global suitability of coffee, cashew and avocado PLOS ONE | https://doi.org/10.1371/journal.pone.0261976 January 26, 2022 10 / 24

(e.g. Nigeria) and South and Southeast Asia (Sri Lanka, the Philippines, Indonesia, Cambodia, Myanmar), primarily due to increasing annual temperatures and in few regions (e.g. parts of Panama or Sri Lanka) due to higher precipitation. Fig 4. Current suitability and expected changes by 2050 for coffee in Vietnam. A current landscape and soil suitability, B current climate suitability, C current overall suitability, D suitability change under RCP 2.6 (low emissions), E suitability change under RCP 4.5 (intermediate emissions), F suitability change under RCP 8.5 (high emissions). https://doi.org/10.1371/journal.pone.0261976.g004 PLOS ONE Global suitability of coffee, cashew and avocado PLOS ONE | https://doi.org/10.1371/journal.pone.0261976 January 26, 2022 11 / 24

The expected changes in cashew suitability due to climate change in the four major cashew producing countries is shown in Table 4. Both in Coˆte d’Ivoire and Benin, a large proportion of the highly suitable (S1) areas are expected to become less suitable (S2) by 2050 due to increasing annual temperatures. In Coˆte d’Ivoire, the expected reduction in S1 is 16% (RCP 4.5) to 32% (RCP 8.5), and in Benin 55% (RCP 2.6) to nearly 100% (RCP 8.5). In the northern parts of both countries, long dry seasons limit cashew suitability. In India and Vietnam, both positive and negative changes in suitability might occur. In North India, positive changes are expected due to higher minimum temperatures of the coldest month, while in South India and Northeast India the negative changes will dominate, mostly due to increasing precipitation. In total (Table 4), the highly suitable (S1) areas will decrease by 16% (RCP 2.6) to 40% (RCP 8.5), whereas both S2 and S3 will increase by 4% (RCP 2.6) to 9% (RCP 8.5). In Northern and Cen- tral Vietnam, positive suitability changes are expected, while in the South suitability decreases. For both positive and negative changes, it is mainly increasing annual temperatures which are responsible in the respective regions. In Vietnam (Table 4), S1 will increase by about 35% in all scenarios, while S2 will decrease by 9% (RCP 2.6) to 7% (RCP 8.5) and S3 by 7% (RCP 2.6) to 11% (RCP 8.5). Unsuitable areas will show a slight decrease in general. Current avocado suitability The avocado suitability under current climatic conditions (Fig 3) revealed large regions with

high suitability (S1 & S2) in Central and South America (e.g. Honduras, Venezuela, Bolivia, Brazil), in West and Central Africa (e.g Coˆte d’Ivoire, Cameroon, Central African Republic, the Democratic Republic of the Congo, the Republic of the Congo, Uganda), and in South and Southeast Asia (e.g. India, Sri Lanka, Vietnam, Cambodia, Thailand, Myanmar, Indonesia). Fig 5. Suitability change for coffee by 2050 according to RCP 4.5 (intermediate emissions). A Central and South America, B West and Central Africa, C South and Southeast Asia. https://doi.org/10.1371/journal.pone.0261976.g005 PLOS ONE Global suitability of coffee, cashew and avocado PLOS ONE | https://doi.org/10.1371/journal.pone.0261976 January 26, 2022 12 / 24

The minimum temperature of the coldest month and the annual precipitation are the two most limiting factors in the suitability model. The boundaries of the avocado growing regions in North and South America, southern Africa and northern Asia, as well as in certain moun- tain regions, are limited by low minimum temperatures in the coldest month. The annual pre- cipitation limits avocado suitability both in wet (Central America, West Africa, Southeast Asia) and dry regions (Eastern Brazil, East Africa, Australia, northern boundaries in Africa) because avocado has a narrow precipitation optimum (see Table 1). Only in a few regions do long dry seasons limit avocado suitability. Compared to climatic criteria, land and soil criteria only play a minor role in the global avocado model with low soil pH (Amazon basin, Congo basin, Borneo) and unfavourable soil texture (Central America, Central Africa), limiting suit- ability in few regions. In the four main producing countries investigated (Mexico, the Dominican Republic, Peru, Indonesia), avocado suitability is also mainly limited by low and high precipitation and low minimum temperatures of the coldest month (Table 5). Regarding the land and soil criteria, Fig 6. Current climate suitability for cashew in India. A current suitability of mean annual temperature, B current suitability of mean minimum temperature of the coldest month, C current suitability of mean annual precipitation, D suitability of the length of the dry season, E overall current climate suitability. https://doi.org/10.1371/journal.pone.0261976.g006 PLOS ONE

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only limited regions are affected by soil texture and slope in all four countries and by low soil pH in Peru and Indonesia. Future avocado suitability The climate change scenario models revealed both positive and negative impacts on avocado suitability in different regions by 2050 (Fig 8). Positive changes due to increasing minimum temperatures in the coldest month are mainly identified at the northern and southern bound- aries of the growing regions in America (the USA, Brazil, Uruguay, Paraguay, Argentina), Africa (Angola, Zambia), Asia (North India, China) and Australia. In sub-Saharan and East Africa (e.g. Burkina Faso, Nigeria, Chad, Ethiopia, Uganda, Kenya) and parts of India, positive changes in suitability are caused by increasing precipitation. Regions of mainly negative impacts are due to drier (e.g. Venezuela, Eastern Brazil) or wetter conditions (e.g. Central Africa, Indonesia, the Philippines). Both positive and negative impacts are expected in Central America, West Africa and Southeast Asia (e.g. Vietnam, Myanmar) based on changes in tem- perature or precipitation. On the one hand (Table 5), the highly suitable (S1) areas will decrease globally by 14% (RCP 2.6) to 41% (RCP 8.5). On the other hand, S2 areas will increase Table 4. Suitable cashew growing areas globally and in main producing countries (S1: Highly suitable, S2: Moder- ately suitable, S3: Marginally suitable, N: Unsuitable) for current (2000) and future (2050) conditions under three RCPs: 2.6 (low emissions), 4.5 (intermediate emissions), 8.5 (high emissions). Expected changes in suitable areas

are given as a percentage. RCP 2.6 RCP 4.5 RCP 8.5 Suit Class 2000 (km2) 2050 (km2) Δ (%) 2050 (km2) Δ (%) 2050 (km2) Δ (%) World total S1 1,909,945 2,236,263 17.1 2,271,876 18.9 2,199,364 15.2 S2 9,512,602 9,705,504 2.0 9,817,983 3.2 10,120,530 6.4 S3 8,628,977 9,472,204 9.8 9,570,975 10.9 9,725,958 12.7 N 104,448,211 103,085,763 –1.3 102,838,901 –1.5 102,453,881 –1.9 Vietnam S1 51,682 70,861 37.1 68,820 33.2 68,827 33.2 S2 169,992 154,264 –9.3 157,493 –7.4 158,329 –6.9 S3 44,266 41,088 –7.2 40,028 –9.6 39,299 –11.2 N 53,442 53,170 -0.5 53,042 -0.7 52,928 –1.0 India S1 9,278 7,770 –16.3 6,546 –29.4 5,568 –40.0 S2 157,456 163,086 3.6 164,258 4.3 171,194 8.7 S3 315,272 328,034 4.0 332,251 5.4 331,303 5.1 N 2,566,359 2,549,476 –0.7 2,545,311 –0.8 2,540,302 –1.0 Coˆte d’Ivoire S1 18,165 18,084 –0.4 15,222 –16.2 12,307 –32.2 S2 190,087 190,168 0.0 193,030 1.5 195,945 3.1 S3 38,135 38,135 0.0 38,135 0.0 38,135 0.0 N 70,773 70,773 0.0 70,773 0.0 70,773 0.0 Benin S1 2,848 1,280 –55.1 623 –78.1 2 –99.9 S2 25,283 26,850 6.2 27,507 8.8 28,128 11.3 S3 14,917 14,917 0.0 14,917 0.0 14,917 0.0 N 72,079 72,079 0.0 72,079 0.0 72,079 0.0 https://doi.org/10.1371/journal.pone.0261976.t004 PLOS ONE Global suitability of coffee, cashew and avocado PLOS ONE | https://doi.org/10.1371/journal.pone.0261976 January 26, 2022 14 / 24

by 12% (RCP 2.6) to 20% (RCP 8.5) and S3 areas by 6% (RCP 2.6) to 8% (RCP 8.5), while the global unsuitable areas will slightly decrease. According to the model, in all four main producing countries investigated (Mexico, the Dominican Republic, Peru, Indonesia), both positive and negative changes in avocado suitabil- ity due to climate change will occur in different regions by 2050 (Table 5). They can be explained mainly by the expected changes in precipitation patterns (both wetter and drier con- ditions causing positive or negative changes) and to a smaller extent by increasing minimum temperature of the coldest month (positive changes). In Mexico (Fig 9 and Table 5), the posi- tive changes tend to dominate, with increases in S1 (by 87% [RCP 2.6] to 66% [RCP 8.5]) and S2 (by 15% [RCP 2.6] to 21% [RCP 8.5]), and S3 and N areas slightly decreasing. Based on the RCP 4.5 intermediate emissions scenario (Fig 9), future avocado suitability in Mexico is mainly restricted by climate suitability, which is mainly due to the expected mean annual precipitation and the minimum temperature of the coldest month. In the Dominican Republic, the highly suitable (S1) areas will decrease by 59% (RCP 2.6) to 85% (RCP 8.5) and the marginally suit- able (S3) areas by 10% (RCP 2.6) to 16% (RCP 8.5), while the moderately suitable (S2) areas will increase by about 30% in all scenarios. In Indonesia, S1 areas will decrease by 40% (RCP Table 5. Suitable avocado growing areas globally and in main producing countries (S1: Highly suitable, S2: Mod-

erately suitable, S3: Marginally suitable, N: Unsuitable) for current (2000) and future (2050) conditions under three RCPs: 2.6 (low emissions), 4.5 (intermediate emissions), 8.5 (high emissions). Expected changes in suitable areas are given as a percentage. RCP 2.6 RCP 4.5 RCP 8.5 Suit Class 2000 (km2) 2050 (km2) Δ (%) 2050 (km2) Δ (%) 2050 (km2) Δ (%) World total S1 790,882 682,815 –13.7 626,928 –20.7 464,091 –41.3 S2 8,150,219 9,121,096 11.9 9,447,321 15.9 9,763,580 19.8 S3 12,503,581 13,248,676 6.0 13,234,520 5.8 13,497,956 8.0 N 103,062,026 101,454,122 –1.6 101,197,940 –1.8 100,781,081 –2.2 Mexico S1 829 1,548 86.7 1,420 71.3 1,373 65.6 S2 93,712 107,578 14.8 111,375 18.8 112,949 20.5 S3 416,740 411,218 –1.3 405,629 –2.7 406,587 –2.4 N 1,417,134 1,408,071 –0.6 1,409,991 –0.5 1,407,506 –0.7 Dominican Republic S1 3,964 1,632 –58.8 1,194 –69.9 596 -85.0 S2 15,333 19,644 28.1 20,221 31.9 20,275 32.2 S3 15,754 14,111 –10.4 13,314 –15.5 13,320 -15.5 N 11,807 11,470 -2.9 12,128 2.7 12,667 7.3 Peru S1 11,814 5,399 -54.3 4,043 –65.8 2,817 –76.2 S2 92,971 91,394 –1.7 93,042 0.1 95,393 2.6 S3 162,120 164,745 1.6 155,237 –4.2 156,678 –3.4 N 1,005,178 1,010,545 0.5 1,019,761 1.5 1,017,195 1.2 Indonesia S1 8,286 5,002 –39.6 3,607 –56.5 2,874 –65.3 S2 153,705 156,022 1.5 144,982 –5.7 143,972 –6.3 S3 422,596 440,551 4.2 372,775 –11.8 370,961 –12.2 N 1,242,637 1,225,648 –1.4 1,305,859 5.1 1,309,415 5.4

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Fig 7. Suitability change for cashew by 2050 according to RCP 4.5 (intermediate emissions). A Central and South America, B West and Central Africa, C South and Southeast Asia. https://doi.org/10.1371/journal.pone.0261976.g007 Fig 8. Suitability change for avocado by 2050 according to RCP 4.5 (intermediate emissions). A Central and South America, B West and Central Africa, C South and Southeast Asia. https://doi.org/10.1371/journal.pone.0261976.g008 PLOS ONE Global suitability of coffee, cashew and avocado PLOS ONE | https://doi.org/10.1371/journal.pone.0261976 January 26, 2022 16 / 24

2.6) to 65% (RCP 8.5). Except for RCP 2.6, where S2 and S3 areas will increase by 2% and 4%, respectively, S2 (-6%) and S3 (-12%) suitability is also expected to decrease. In Peru, the nega- tive changes are expected to dominate in all scenarios with S1 decreasing by 54% (RCP 2.6) to 76% (RCP 8.5). Fig 9. Future suitability for avocado in Mexico and expected change by 2050 based on RCP 4.5 (intermediate emissions). A Overall future suitability, B suitability change by 2050, C current landscape and soil suitability, D future climate suitability, E future suitability of mean annual temperature, F future suitability of mean minimum temperature of the coldest month, G future suitability of mean annual precipitation, H suitability of the length of the dry season. https://doi.org/10.1371/journal.pone.0261976.g009 PLOS ONE Global suitability of coffee, cashew and avocado PLOS ONE | https://doi.org/10.1371/journal.pone.0261976 January 26, 2022 17 / 24

Discussion Current crop suitability compared to main producing regions As could be expected by the biophysical requirements of coffee, cashew and avocado (Table 1), both temperature and precipitation criteria represented the most limiting factors for the suit- ability of the three crops in different regions. However, for all three crops, low soil pH was shown to be an additional important limiting factor in South America (Amazon basin), Cen- tral Africa (Congo basin), Southeast Asia (e.g. Sumatra, Malaysia, Borneo, New Guinea). In certain regions, also steep slopes and unfavourable soil texture were identified as important limitations. We therefore conclude that the integration of topographic and soil factors is cru- cial for improving current and future crop suitability modelling, especially on a regional or local scale. The modelled global suitable regions of coffee, cashew and avocado comprise most major producing countries based on FAOSTAT (www.fao.org/faostat). For coffee arabica, suitable growing regions were identified in all major producing countries. In our analysis, however, certain major cashew producing countries (India, Senegal, Guinea-Bissau, Mali, Burkina Faso) resulted in low cashew suitability. Some of the growing regions in these countries were rated as unsuitable because they have a dry season lasting longer than six months. We therefore con- clude that this criterion is either too restrictive with cashew being a drought tolerant crop [24], or that irrigation during the dry season is required in these regions. When changing the length

of the dry season for unsuitable areas (N) from more than six to more than seven months, the major growing regions in India and West Africa lie within the suitable area. Similarly, suitable avocado growing areas were found in most but not all major producing countries and regions according to our model. Some of the growing regions of Peru (coastal area), the USA (Califor- nia), Chile, South Africa, Spain, Morocco, Israel and Australia were rated as not suitable for avocado cultivation. On the one hand, this limitation is due to insufficient annual precipitation in some of these regions, where avocados are in fact irrigated [30]. On the other hand, low minimum temperatures in the coldest month co-limit suitability in some of these regions, indicating that this criterion could be too restrictive. This is supported by Wolstenholme [30] who reported growing areas with minimum temperatures during the coldest month of below 8˚C (rated as ‘unsuitable’ in our model) in parts of California, Israel, New Zealand, South Africa and southern Australia. However, the same author also mentioned the importance of good site selection and management practices from the point of view of frost in order to reduce frost damage in these marginal areas. Shifts in crop suitability due to climate change When taking into account climate change scenarios, shifts in suitable growing regions are expected for all three crops, with both some of today’s suitable growing regions disappearing and new ones emerging. Compared to cashew and avocado, climate change has the highest

negative impact on currently suitable coffee growing regions because of its greater suscepti- bility to high temperatures. While cashew suitability is also negatively affected by rising tem- peratures in certain regions, avocado is more affected by changes in precipitation (both negatively and positively). All three crops, however, profit from increasing minimum tem- peratures at high latitudes and high altitudes. The impacts of the three RCPs (2.6, 4.5 and 8.5) applied in our model generally show similar patterns. For coffee, the negative impacts on current growing regions clearly intensify from RCP 2.6 to 8.5. The same is true for cashew and avocado, where both positive and negative global as well as regional trends intensify from RCP 2.6 to 8.5. PLOS ONE Global suitability of coffee, cashew and avocado PLOS ONE | https://doi.org/10.1371/journal.pone.0261976 January 26, 2022 18 / 24