**1. Introduction**

Sustainability can be defined as improving the quality of human life while living within the carrying capacity of supporting ecosystems [1]. Common frameworks to sustainability may include dimensions of social, economic, environmental, cultural and political needs [2]. Some take the perspective that humans and environment are separate and therefore the major role humans play in the environment is destructive and extractive [3,4]. This sits in opposition to indigenous epistemology that views people as an integral part of the environment—a concept is that is captured in biocultural frameworks, in which we take into consideration relationships between biological and cultural systems in order to conceptualize the link between people and environment [5,6]. Biocultural refers to how human cultures are shaped by their surrounding ecosystems, which in turn, shapes culture itself [6]. This approach is not a new concept by any means but has implications for use today in terms of sustainable management practices. There is an "inextricable link" between cultural diversity and biodiversity and there has been insight on correlation between the two phenomena that illustrates their importance for the resilience of social-ecological systems that sustain life [3,6]. The preservation of cultures and the restoration or protection of the environment are therefore dependent on the other, not only in natural ecosystems but in human managed systems such as agriculture.

Including cultural aspects into environmental approaches is known to lead to sustainable management practices and more resilient systems [6]. Customary values and community capital in Hawai'i facilitate reciprocity and food sharing and the passing of knowledge which can help sustain resources over time and provide effective natural resource management approaches [7]. Community involvement and cultural perpetuation of values is crucial to long term food security and can lead to greater chance of long term success in restoration [7,8]. These cultural perpetuations are likely tied, at least in part, to the key biological species through which biocultural relationships are formed. It terms of losing biocultural diversity, the globalization of food systems and unsustainable agriculture development are substantial contributors [6,9]. Hawai'i has been no exception, with plantation agriculture arguably being the largest driver to cultural displacement and loss over the past 200 years. However, within the last forty years, revitalization of traditional agriculture has increased, paralleling an increase in cultural revival. While there are several crops that hold importance in terms of Hawaiian culture, we focus on the role of breadfruit (*Artocarpus altilis*, (Parkinson, Fosberg)) within contemporary commercial agriculture to explore its broader applications for sustainability in Hawai'i. We argue that in Hawai'i, traditional agriculture plays a pivotal role in the connection between the socioeconomic and cultural aspects of sustainability and follow Barthel et al. [5] in arguing that supporting crops with biocultural importance is critical for long-term success of agriculture. Furthermore, the use and maintenance of such crops is essential for maintaining cultural values and practices, particularly within the modern socioeconomic landscape, and for the health of the environment.

#### *1.1. Traditional Breadfruit Cultivation in Hawai'i*

Breadfruit, or 'ulu in Hawaiian, is a tropical tree in the fig family [10] that produces a large (typically 1–3 kg) starchy fruit that tastes much like a potato, banana or plantain depending on the state of maturity (Figure 1). Breadfruit has been consumed as a staple crop throughout Oceania for millennia, appears in many aspects of traditional knowledge, has influenced sociopolitical environments and has multiple resource applications. A sterile, seedless variety of breadfruit was transported to Hawai'i at least 800 years before present [11,12].

Hawai'i, when compared to smaller and more ancient islands of the Pacific, expresses greater opportunities for agricultural development [13] and consequently, Native Hawaiian populations were heavily reliant on intensive cultivation of land [14]. This afforded the emergence of unique agricultural practices, such as mahi'ai—massive, intensive rainfed field systems Lincoln et al. [13] *in this issue*. Breadfruit grows well in marginal habitats and, throughout most of the Pacific, was an important staple crop, often seen as a "gift from the gods" and grown in semi-wild "food forests" with minimal active management [15]. However, in Hawai'i, where extensive cultivation of annual starches was possible, breadfruit assumed a complimentary role and was used to expand cultivable areas [16], increase resilience [17] and enhance place-adapted cropping systems [18]. While breadfruit trees maintained near households were managed much like elsewhere in the Pacific, large-scale breadfruit arboriculture took on a different form in Hawai'i. In addition to the semi-wild and largely unmanaged "food forests," Hawai'i developed breadfruit arboriculture that was well-spaced, highly managed and incorporated the intensive cultivation of multiple annual and perennial crops [11,16].

In Hawai'i, breadfruit likely started as part of individual garden plots near settlements, expanded into semi-wild food forests cultivated on colluvial valley slopes and culminated into the development of sizeable, systematic arboriculture [11,13,16]. Such arboricultural developments cultivated breadfruit within intercropped agroforestry systems planted with kukui (candlenut, *Aleurites moluccanus*), 'ohi'a ¯ 'ai (mountain apple, *Syzygium malaccense*), 'uala (sweet potato, *Ipomoea batatas* L.), maia (banana, *Musa spp*), uhi (yam, *Dioscorea alata*), kalo (taro, *Colocasia esculenta*), ko (sugar cane, ¯ *Saccharum officinarum*), wauke (paper mulberry, *Broussonetia papyrifera*), 'olena (turmeric, *Curcuma longa*), pia (arrowroot, *Tacca leontopetaloides*), 'awa (kava, *Piper methysticum*), 'awapuhi (shampoo ginger, *Zingiber zerumbet*) and k¯ı (t¯ı, *Cordyline fruticosa*) [19–21]. These rainfed systems comprised a significant portion of the total agriculture [18,22], created habitat that allowed the optimal cultivation of some crops such as wauke [20] and produced a highly diverse set of food, resource and medicine crops [16].

**Figure 1.** The large fruit and leaves of the Hawaiian breadfruit tree.

### *1.2. Traditional Importance of Breadfruit in Hawai'i*

Breadfruit has made substantial contributions to food production, health and nutrition, environmental quality and culture in the Hawai'i for centuries [11,15,23]. 'Ulu was a staple food source in addition to kalo, 'uala, uhi and mai'a, ranking third in importance for complex carbohydrates and serving as an essential crop in times of human and environmental disturbances [11,22,24]. The fruit is nutritious, especially when compared to contemporary starches such as rice, corn and wheat [25]. 'Ulu trees are relatively low maintenance but provide substantial yields, resulting in high surplus production after establishment. Breadfruit was seasonally abundant but unlike elsewhere in the Pacific, storage of breadfruit in underground pits appears to have been rare, while application as an animal feed appears to have been more extensive [15,26].

Breadfruit was also a valuable resource and medicine. A long list of uses for wood includes; housing and construction, canoes, surfboards, drums, cloth and poi (fermented taro with water) boards, all of which could be polished with its leaves that were used as an abrasive similar to sandpaper [11,15,27]. Virtually all parts of the plant are used medicinally–the leaves, bark, fruit, flowers and latex–to treat ailments including skin conditions, high blood pressure, cardiovascular disease; the flowers are commonly used to repel mosquitos; and the high-latex sap also has an array of applications, including caulking and bird snaring [11,15,27,28].

The development of tree resources, such as breadfruit, can be seen as investing into the land to develop long-term resources for future prosperity [29]. The development of large-scale arboriculture, such as the famous breadfruit groves of Kona and Lahain ¯ a, took place during the "golden age" of ¯ Hawai'i in the 16th century [13,30], with the resulting surplus of production further empowering the development of sociopolitical complexity and hierarchy [31–33]. Due to the nature of political and

labor organization, extensive systems of agriculture were able to form over time, ensuring the ability for ancient Hawaiians to spend more time into shaping political dynamics. The groves of breadfruit acted as a significant resource that was driven by the desire to increase local economies, which in turn developed stronger political hierarchies (through taxes, military service, etc.) that could further invest into the landscape [16,17].

The seasonal surplus of breadfruit may have powered social dynamics and rituals, such as the emergence of the Makahiki—an extended period where work and certain religious ceremonies were suspended and corresponding to a time of increased recreation and tax collection [34,35]. During Makahiki, breadfruit served many ritualistic purposes including the shaking of the Maoloha net at the end of Makahiki; if the food dropped from the net, there would be no famine during next growing season [34]. The occurrence of the festival in October to January corresponds well with the surplus breadfruit season. The Makahiki developed out of Kona, which was famous for the "breadfruit belt" (expansive stretch of agroforestry largely consisting of breadfruit that crossed over several regional districts throughout the Kona Field System of Hawai'i Island) [14]. One could argue that such an extended period of ceremony could only be made possible by an extensive surplus. This would be similar to other Pacific Islands, where annual time periods that corresponded to religious and ceremonial occurrences aligns with the productive periods of breadfruit and other crops [15,36]. While speculative, that the most famous ceremony of abundance in ancient Hawai'i developed in a region famous for its breadfruit and coincided largely with the season of breadfruit productivity suggests a linkage between 'ulu and abundance.

The abundance from 'ulu also has an important place in Hawaiian cosmology. Stories include that of the god Ku who turned himself into an 'ulu tree to feed his starving wife and children [ ¯ 14]. Breadfruit was depicted in stories of embodiment, in which the gods would enter a breadfruit tree in supernatural form, signifying a close relationship and admiration of the natural world [11]. Many concepts of Hawaiian traditions and values are captured in a range of 'olelo n ¯ o'eau (Hawaiian proverbs, sayings or ¯ stories) that utilize 'ulu as a metaphor for wealth, success and planning. The reoccurring lessons utilize breadfruit to teach values on sharing and hospitality, warnings to be kind to travelers and making sacrifices for the prosperity and success of others [37,38].

#### *1.3. Loss of Traditional Food Systems*

The arrival of Europeans in the 18th century marked a decrease in the native Hawaiian population and greatly altered the path of Hawaiian agriculture. This shift resulted in the decline of traditional systems, the establishment of plantation agriculture, the marginalization of native peoples and reshaped the future of Hawai'i [1]. As with all traditional crops, the abundance of breadfruit in Hawai'i declined precipitously (see Kagawa-Viviani et al. *in this issue*).

Upon arrival, early European explorers reported seeing considerable breadfruit groves around all the islands, especially near villages and settlements, with vast arboricultural "belts" in several regions [11,13]. The Kona breadfruit belt was modeled to have consisted of more than 100,000 trees; it is now, however, reduced to a few hundred trees, often neglected and unwanted [16]. These traditional, intercropped systems once produced enough food to sustain the largest population in Polynesia and indeed supported a larger population on each island (excluding O'ahu) than exists today [39,40].

Local economies, cuisines, cultural practices and the state of the environment shifted with the decline in traditional agriculture. Today, 80–90% of food is imported, making Hawai'i one of the most dependent states in the United States [41]. Recently, Hawai'i was assessed as the 48th worst state in terms of farming outlook [42]. Statewide dietary shifts to processed, imported foods have raised public health concerns. Hawaiians and other Pacific Islanders are especially vulnerable to dietary-based health issues, including obesity and diabetes, which have risen alarmingly fast, holding some of the highest rates in the world [25]. Furthermore, we see exceptionally negative environmental impacts that threaten soil, water, ecosystems and human health [43]; and the declining involvement in local food production greatly reduces the overall food security [1] of Hawai'i [44].

With the reduction of breadfruit and other crops, there are fewer opportunities for communities to engage with and learn about them. Furthermore, with decreased number of farms and the connection to cultural foods, there are fewer opportunities to connect with the land, learn cultural practices involving Hawaiian agriculture and to gather around Hawaiian food. It takes time for food to become cuisines and acquire symbolic meanings and once lost the efforts needed to restore those relationships are significant [24].

#### *1.4. Resurgence for Local Food and Breadfruit in Hawai'i*

In the 1970s, public awareness increased demands for local, fresh and healthy foods [1]. Coinciding with a growing interest for food self-sufficiency, a resurgence of Hawaiian culture, pride and practices also occurred in what is affectionately known as the "Hawaiian renaissance." These parallel movements coupled with research efforts regarding breadfruit, led to increased demand for fresh breadfruit in Hawai'i. Grassroots and institutional efforts partnered to conduct multiple campaigns to promote the cultivation, application and consumption of breadfruit in Hawai'i [45]. Such efforts included public education, festivals and tree-giveaways. Part of the challenge to popularize breadfruit was due to a social stigma that positioned breadfruit as a second class food in Hawai'i [46]. While outreach programs, marketing, availability, introduction of value-added products and presence in restaurant dishes has educated new users about breadfruit, the stigma was not as easy to overcome. Finding an appropriate role for breadfruit in cultural and agricultural contexts remains an ongoing challenge.

More recently, ecosystem-based management strategies are being promoted for agriculture and conservation [47]. The state government has recognized efforts to strengthen community-based conservation and set goals to have more sustainable and secure food systems in Hawai'i [44,47], while large landowners have similarly promoted improved practices to agricultural leaseholders. However, overall there has been a significant disconnect between stated goals and outcomes [48–50]. Breadfruit cultivation has the ability to contribute to these efforts and more.

#### **2. Materials and Methods**

We used a combination of surveys (Table A1), semi-structured interviews (Table A2) and onsite farm observations with 43 individuals and organizations engaged in breadfruit production (Figure 2). Of the 43 participants, 36 were bonafide agricultural producers, while the remaining were non-profit organizations growing breadfruit for preservation, cultural access and community food systems. Participants were initially recruited through open advertisement and targeted approach of well-known growers, with subsequent requests made using a "snowball" approach; all participants that expressed interests were included in the study. Participants represented a range of social and natural environments and included new and long-time farmers. Participants were selected by word of mouth, community connections, internet searches and qualified to participate if they cultivated at least ten breadfruit trees. The breadfruit farmers who engaged in the study are referred to as "participants". The participants varied in their experience of farming breadfruit but were all successful in growing trees that produced fruit and were therefore an expert subset of the general population. The study was conducted on various locations on the islands of Hawai'i (n = 19), O'ahu (n = 15), Kaua'i (n = 5) and Maui (n = 4). Interviews and surveys were conducted onsite beginning in March 2017 and finalized in May 2018, during the spring season (March-May) of each year.

Ethnographic data was collected in two forms; interviews and surveys. Informed consent was received for all participants and survey and interview scripts were granted IRB exemption for work with human subjects. The survey questions focused on the history of the farm and the trees, cultivation techniques, farming practices and tree care methods (Table A1). The interviews were semi-structured and probed the participants on their beliefs, concerns, lessons and ideas concerning breadfruit, contemporary culture and agriculture (Table A2). The interviews, in general, focused on the role breadfruit plays in the connection between culture and place and how those connections provide for the well-being of people and the environment of Hawai'i today. Interview duration was variable, lasting between one-half hour and three hours depending on the individual's willingness and enthusiasm to share information. Quotations and activities reported from the interviews stem solely from the bona-fide agricultural producers and does not pull from the non-profit participants. Survey data was managed and organized in Excel 16.13 (Microsoft Corporation, Redman, WA, USA) and analyzed in SPSS 20.0 (IBM, Armock, NY, USA). Written notes from the interviews and on-site observations were pinned to survey results and coded for thematic descriptions by the authors. Often repeated themes were selected for emphasis and specific farm examples were pulled to demonstrate each theme.

**Figure 2.** A map of the breadfruit producers that participated in the survey and interview portions of the study.

Participation included on-site sampling to assess soil and tree health at each site. Soil samples were retrieved from each site; composite soil samples were collected by mixing three soil cores taken 2 m from the trunk of the trees at a depth of 30 cm. Soils were assessed for pH and soil moisture in house, then dried, sieved, ground and packaged for analysis at Brookside Laboratory Inc. (New Bremen, OH, USA). Tree health was assessed through chlorophyll and photosynthetic measurements. Chlorophyll counts were measured using a SPAD 502 Plus Chlorophyll Meter (Spectrum Technologies, Aurora, IL, USA) and photosynthetic rates were measured using a miniPPM-100/150 Plant Photosynthesis Meter (EARS, Delft, The Neatherlands). Ten random, consecutive measurements were taken per leaf, with three leaves per tree and three trees per site analyzed (90 total measurements per site); the third leaf from the tip was used for measurement (Lincoln et al. in review). Measurements data was organized in Excel 16.13 and analyzed in JMP Pro 13 (SAS Institute, Cary, NC, USA).
