Artocarpus (around 70 species) is a plant genus of Moraceae native to South and Southeast Asia, with Borneo serving as a diversification hotspot. The genus contains numerous well-known medium to large tropical tree species. One of the well-known species is breadfruit [Artocarpus altilis (Parkinson ex F.A. Zorn) Fosberg]. This species is a horticultural plant (Rahmah and Waluyo, 2019). with nutritional properties similar to rice, and it is sometimes used as a substitute for rice in some regions of the world (USDA, 2018a, b). Breadfruit trees, in addition to being a prolific producer of nutritious fruits, have the potential not only to adapt, but also to thrive in conditions where other crops would perish. This plant is a staple food in the Pacific Belt and an important component of socio-cultural rituals and the medical system. Under present production standards, breadfruit growing delivers numerous environmental benefits. Breadfruit tree crops in general have been shown to provide numerous benefits, which are amplified in agroforestry settings (Barthel et al., 2013). Agroforestry can renew the soil’s litter layer, improve and maintain soil quality, retain soil nutrients, and reduce soil erosion (Gao et al., 2014; Langston and Lincoln, 2018). Artocarpus is an important staple crop that has been grown for centuries throughout Oceania under agroforestry systems. The crop’s long history and significance are reflected in language, art, and cultures. Breadfruit was recently included in Annex 1 of the International Treaty on Plant Genetic Resources (ITPGR) as one of 35 crops identified for their importance for food security and interdependence, and it is classified as a priority crop by the Global Crop Diversity Trust (http://www.croptrust.org/main/lprioritycrops.php) (Jones et al., 2012).

However, the recent trend toward deforestation, climate changes, and the inclusion of non-traditional cuisines has reduced breadfruit dependency in many Oceanian regions and influence either the breadfruit productivity or nutrient content (Erland et al., 2023). As reliance on bread fruit declines, the threat of genetic erosion grows, and many of these geographically confined cultivars face extinction. Agroforestry land uses are required for sustainable breadfruit production. In fact, current land use change has resulted in the rapid growth of deforestation due to settlement development, which has threatened and reduced the land available for agroforestry practices (Munjeb et al., 2020; Shapla et al., 2022). Deforestation can affect the breadfruit crops in indirect way through climate change impacts. Lima et al. (2022) predicted that climate change following land use changes and deforestation threatens native potential crop species as can be seen in Brazil. Climate change following deforestation is projected to cause a crop species to lose an average of 65% of its original environmentally suitable habitat (Gomes et al., 2019). According to the IPCC study (Tuddenham and Robert, 2022), human activities raise global temperatures by 1 ⁰C over preindustrial levels. Climate change (Ma and Sun, 2018) affects crop species distribution by altering climate parameters such as temperature seasonality, yearly precipitation, and annual mean temperature, resulting in abnormally dry months. The climate has an important role in limiting crop species spread by affecting the life cycle of the crop species by lowering or increasing temperature, precipitation, and wind speed factors. These changes can have an immediate impact on crop species ecology or induce population declines, which can lead to extinction (Masson-Delmotte et al., 2019). Climate change may pose an irrevocable threat to fauna and flora, as well as humans, in the long run.

In Indonesia, breadfruits are distributed all over the country. It is known as a versatile crop since all parts of breadfruit are consumable and can be used by humans (Estalansa et al., 2018). In Indonesia, breadfruit crops were also cultivated within agroforestry systems (Elevitch and Ragone, 2018; Adinugraha et al., 2021). Breadfruit is an important crop since its production is increasing from 35,435 metric tons to 92,014 in just within seven years, covering 13,359 ha. Areas in Indonesia used for breadfruit cultivations to deal with the food security issues covering Sumatra Island, including South Sumatera, Lampung, and Jambi, and Java Island, including West, Central, East Java, D.I Yogyakarta, East Kalimantan, and eastern Indonesia, including East Nusa Tenggara and South Sulawesi (Widowati, 2009). One of the areas with potential in Indonesia for growing breadfruit crops is Central Java. Currently, the existence of agroforestry and crop species in Indonesia is threatened by rapid climate change (Santika et al., 2017; Kemen et al., 2019). One of the areas in Indonesia that is currently threatened by rapid climate change is Java Island (Higginbottom et al., 2018). Central Java is one of the areas on Java Island known for its agroforestry potential and diverse crop species (Rozaki et al., 2021), as well as for breadfruit agroforestry (Purwaningsih et al., 2020), which is recently threatened by climate change. This climate change has the potential to threaten the existence of breadfruit crops and food security. The current study on breadfruit in Indonesia and Java Island focuses mainly on diversity aspects (Rahmah and Waluyo, 2019) (Estalansa et al., 2018), and growth performance (Adinugraha et al., 2021), yet a study on how climate change can impact the potential adaptation of breadfruit is still limited.

Currently, there are a growing variety of methods for estimating habitat appropriateness and suitability, known as species distribution modeling (SDM), including MaxEnt (maximum entropy), BIOCLIM, DOMAIN, generalized additive model (GAM), GLM, and BIOMAPPER. Each tool is unique, with its own set of advantages and disadvantages. According to Marcer et al. (2013), several advantages of SDM include the need for only species presence data, the capacity to run with a limited quantity of data, the high accuracy of prediction results, the high reproducibility, and the ability to predict the most discriminating bioclimatic factors (Fois et al., 2018).

In Indonesia, SDM has been used to estimate several plant species. SDM has been used to simulate Baccaurea angulata Merr. or ‘Belimbing Dayak,’ an underutilized fruit by indigenous people in Kalimantan. This species has the potential to be exploited as both an edible fruit and a therapeutic plant. Unfortunately, the conversion of forests to oil palm and rubber plantations has affect climatic variables and reduces the habitat of B. angulata. The findings indicate that four bioclimatic variables, namely solar radiation in October, altitude, precipitation in the warmest quarter, and slope, are important in determining B. angulata’s suitable environment. The location of acceptable habitat for B. angulata corresponds to its current distribution. The potential appropriate region was substantially larger than the current distribution of B. angulata in Kalimantan. West Kalimantan and South Kalimantan were found as the most suitable places in this study. They comprised sections of Sambas, Landak, Sanggau, Sekadau, and Bengkayang in West Kalimantan Provinces, and Tanah Laut and Banjar in South Kalimantan Provinces. It is shown that the SDM was extremely accurate and informative for B. angulata habitat suitability and potential distribution. The anticipated model of appropriate sites can be used for B. angulata management, monitoring, cultivation, and future conservation (Gunawan et al., 2021). Then SDM method has potential to be used to assess the potential cultivation areas for breadfruit.

Despite the potential of breadfruit agroforestry, particularly in Central Java, there is very little information on this crop species’ potential cultivation areas and how it is whether threatened or supported by current climate changes. This information is very important considering there are 145 million people living on Java Island, and the food security of the people depends on the available crops. Here, we used a SDM approach to (1) quantify potential breadfruit cultivation areas and then (2) assess potential cultivation areas that were impacted by climate change. The results will contribute significantly to sustaining the agroforestry practices of this species over the long term.

The A. altilis presences recorded during the surveys were parts of the agroforestry systems. This finding is in agreement with previous study that clarifies agroforestry are crucial for the breadfruit cultivation practices (Siarudin et al., 2021). In this study, the method to assess the potential cultivation areas for expanding breadfruit is using SDM. The use of this method contributed to better conserve breadfruit habitat using the following approach, first it provided key bioclimatic variables highly correlated with breadfruit distribution. Second, SDM model was developed to quantify the relationship between breadfruit presence and the selected bioclimatic variables including its inverse variables, as reported in this study was climate change (Yi et al., 2016). The uses of SDM in this study to assess the impacts of climate changes on the potential distribution of vegetation were in agreement with the previous study (Ali et al., 2023; Daï et al., 2023).

This study confirmed that Bio 3, Bio 4, Bio 15, and Bio 18 are some fundamental bioclimatic variables shaping the tree species distribution, as reported before (Ali et al., 2023). Those bioclimatic variables were related to the temperature and precipitation aspects. The roles of these climatic variables are very prominent in the distribution of breadfruit in Central Java. Precipitation in the warmest quarter was detected as the leading variable in the distribution of tree species (Rathore et al., 2019). Similarly, isothermality represents the proportion of the mean diurnal range to the annual temperature range. Hence, day and night and summer and winter temperature differences strongly influence the considered tree species. This means that the predicted eastward niche shift for breadfruit in the Central Java region would be chiefly influenced by temperature and precipitation variations. Similar findings were also reported by Su et al. (2005) and Li et al. (2019), who communicated the role of temperature and precipitation factors in tree species distribution. Breadfruit-suitable cultivation areas are expected to expand due to precipitation. Increased precipitation during the driest quarter and overall increases in annual precipitation cause the prospective expansion of suitable breadfruit areas at the periphery of the baseline acceptable range (Zhao et al., 2020; Yang et al., 2022).

Temporal and climate change dimensions can have potential impacts on vegetation spatial distributions. The impacts can increase the size of distributions or reduce them. In this study, the temporal variation causes an increase in suitable cultivation areas by the year 2070 for both climate change scenarios. By comparing the emission strategies, lowering the emissions will lead to more suitable cultivation areas. This finding confirming the implementation of RCP2.6 will increase suitable areas and RCP8.5 will cause decline was in accordance with the precious study on vegetation (Yu et al., 2023) and particular breadfruit (Yang et al., 2022). According to recent studies, in Southeast Asia, 80.7% of the region, or 3.6 million km², is considered good for breadfruit, while 77.4%, or 2.8 million km², is considered fair. A recent study also confirmed the adaptability of breadfruit against climate change scenarios. In the Southeast Asia region, the breadfruit-suitable area primarily persists and even increases by 0.7%, or equal to 23000 km², under the RCP2.6 scenario and by 0.8%, or 30000 km², under the RCP8.5 scenario. A study from the tropical Hawaii Islands (Mausio et al., 2020) confirmed successive increases in breadfruit suitability in the RCP4.5 and RCP8.5 scenarios, with an increase of 27% for RCP4.5 and 89% and for RCP8.5, respectively. Then, it concludes that breadfruit is a potential crop at least until 2070 that can adapt to climate change situations in which the optimum results can be gained by investing more in climate change mitigation strategies.

The shifting of breadfruit to the east under climate change, where eastern parts of central Java have higher temperatures, is in agreement with the current predictions. Breadfruit is considered a crop that can deal with the warming environment due to climate change. However, the potential areas are fragmented. Despite the fact that the east and southeast of central Java are predicted to provide suitable habitats for breadfruit, this area is dominated by mountain ranges. These mountain ranges can provide physical barriers to breadfruit seed dispersal (Qiong et al., 2017). Despite that, the mountain environment has specific local climate characteristics (Porceddu et al., 2020) that limit the presence of breadfruit in some mountainous areas in central Java. The shifting of breadfruit to the east, followed by a reduction some potential habitats, is in agreement with previous studies. In low-altitude areas that are located in the subtropical and tropical regions, climate change will significantly contribute to the reduction of suitable areas of staple crops compared to the crops raised in the higher latitudes (Levis et al., 2018).

The shifting of breadfruit expansions as modeled in this study will lead to ecological and socioeconomic impacts. The model shows that some areas that were previously suitable for breadfruit will disappear, especially in the western region. The reduction of suitable areas will then impose food security in certain areas. In contrast, the expansion of breadfruit eastward will provide opportunities for using breadfruit as an alternative crop in the eastern regions of Southeast Asia. This will mitigate the food security issues in those areas.

In this study, we modeled the current spatial distribution of A. altilis potential cultivation areas, tested the key bioclimatic indicators combined with climate change that could potentially affect distribution, and simulated its suitable cultivation areas. Our results show that the potential cultivation areas of A. altilis follow mostly the precipitation seasonality (Bio 15), precipitation of the driest quarter (Bio 18), and temperature seasonality (Bio 4) gradients. As hypothesized by previous studies, the spatial distribution of A. altilis has the potential to expand by the year 2070 despite its area reductions in the current climate. As can be seen under both optimistic and pessimistic scenarios, the suitable cultivation areas categorized as having high suitability will expand eastward. These expansions will add 536 km² of high-suitability areas under RCP2.6 and 1040 km² for RCP8.5 in 2070. Implementing a mitigation climate change scenario and limiting the temperature increase to only 1°C will provide 270.967 km² more of suitable cultivation areas for breadfruit in 2050 and 133.296 km² in 2070.

The model indicating the potential habitats for breadfruit that are resilient to climate change is mostly in the east of central Java. Then, to anticipate this, the local agriculture authorities are urged to have some preparation. Considering that Java Island is threatened by rapid deforestation and land use changes, regions in the eastern parts considered to have high suitability should be protected immediately from logging, mainly in Kendal District, which is predicted to have the most suitable habitats under climate change. Due to the fact that intensive breadfruit plantations may also lead to logging, alternative solutions should be considered. One alternative that can be taken is agroforestry. In this scenario, breadfruit is grown together with the native woody species.

The original contributions presented in the study are included in the article/supplementary material. Further inquiries can be directed to the corresponding author.

SU: Conceptualization, Writing – review & editing. FL: Conceptualization, Writing – review & editing. AA: Software, Writing – original draft. F: Conceptualization, Writing – review & editing. MRF: Conceptualization, Writing – review & editing. HQ: Project administration, Writing – review & editing.