*7.5. Cropping Systems Associated with Kalo Influenced the Structure of the Hawaiian Social-Ecological System*

Although not a native plant, *kalo* played a major role in the highly intensified management of the ecological subsystem, and its cultivation shaped the cultural landscape that is iconically associated with the Hawaiian social-ecological system. *Kalo* is most productively cultivated in terraced and flooded pond-fields ([54], Figure 5), which resemble rice paddies of South-East Asia. Evidence [27,54,65] suggests that nearly all land capable of being irrigated (from the backs of valleys to the alluvial plains bordering the seashore) was converted from its natural (i.e., pre-human) state of lowland wet-to-mesic forest types; to flooded fields for the cultivation of *kalo*. This flooded-field system of agriculture shaped the social-ecological system around it as described below.

**Figure 5.** Picture of a contemporary flooded- field system in Hawai'i used to cultivate *kalo* (taro, *Colocasia esculenta*). In this style of agricultre, rivers/streams are the central component with its waters being diverted over large areas of adjacent flatlands for the cultivation of *kalo*.

The conversion of large areas of lowland forest into flooded-field systems had three major repercussions which directly influenced the structure and function of the Hawaiian social-ecological system, as well as the outward appearance of its associated cultural landscapes [66]:

1. This conversion induced localized regime shifts in large areas of land (valley floors and alluvial plains) from forest biome to riparian ecotone. This, in essence, expanded and stabilized riparian habitat—a highly productive ecotone—from a relatively limited to a very broad area. Archaeological evidence suggests that such localized regime shifts have occurred [67], and likely extended the range of native water (i.e., riparian) fowl allowing for increases in their populations [68].


Each of the above occurrences turned out to be key components to the structure and function of the social-ecological system that existed due to the intensified resource management system of ancient Hawaiian civilization known as the *Moku* System [25]. The ecosystem services provided likely enabled a population boom in the Hawaiian social-ecological system that was sustained until contact with Europeans in 1778 A.D., which subsequently brought unexpected and catastrophic change such as a 90% population collapse resulting from introduced diseases [48].

#### *7.6. Substitution of a Social-Ecological Keystone Alters the Structure of Social-Ecological Systems*

An example of resilience is seen in the functional group "crop grown in rain-fed field systems" (Table 2), which has *'uala* as a co-dominant with *kalo*. Rain-fed cropping systems existed in regions in the Hawaiian archipelago that lacked suffient water for large-scale *kalo* cultivation (either through rain or surface water). Areas such as this—as in the *moku* (districts) of Kohala Hema, Kona Akau and Kona Hema on the island of Hawai'i—had field systems which were shaped around *'uala*, the co-dominant in rain-fed systems. Lincoln et al. [39] point out that *kalo* was succeeded by *'uala* in regions where *kalo* could not be cultivated on a large scale due to insufficient water availability. In other words, the dominant of a key biocultural functional group (i.e., the keystone of that biocultural functional group) was substituted by one of the redundant components in that functional group.

Theoretically, this would result in a structural shift within the system, and would look different from the one that was shaped around the cultivation of *kalo* in flooded-field systems. Indeed, we argue that an "alternative regime state" existed in different regions within the Hawaiian social-ecological system where *'uala* became dominant. An "alternative regime state" exists when one keystone is succeeded by another in the context of the same social-ecological system. Contemporary analysis of archaeological and historical evidence [27,39,69] supports the notion that this has occurred, and indicates that *'uala* cultivation was the keystone component of social-ecological systems in the Hawaiian islands in regions lacking sufficient water for intensified cultivation of *kalo*. In this case, manifestations were seen in the emergence of religious sects where a shift in primary deities that elevated Lono over Kane and the emergence of new rituals and traditions, such as the *makahiki* festival that originated on the leeward side of Hawai'i Island. Further differences have been evidenced in the stability of the political hierarchy and the propensity for predatory warfare.

While these large-scale differences of the structure of the social-ecological system in places where it was shaped around *'uala*—as opposed to *kalo*—are observable, a detailed investigation would likely reveal many more subtle changes at the local level. *Kalo* expresses extreme dominance in key functional groups such as relation to the family system and the genesis of mankind. How did the local biocultural relationships evolve in the absence of *kalo*? The redundancy within the agricultural functional groups allowed for the existence of the Hawaiian social-ecological system in arid regions, albeit one of altered form and structure. In ecological analogy, an "alternative regime state" would be akin to replacing the dominant canopy tree in a forest, with cascading effects on the assemblage of bird, animal and insect species present, while a "regime shift" might be shifting from a forested ecosystem to a shrubland, and all the associated shifts in supported species. Similar regime shifts have also been explored by Scheffer et al. [70].

#### **8. Conclusions**

#### *8.1. On Keystone and Redundant Components within Social-Ecological Systems*

Social-ecological systems are composed of linked biological-sociocultural relationships, and can be referred to as the "biocultural elements" of these systems. "Keystone" components and "redundant" components exist within the set of biocultural elements that compose social-ecological systems. Theory and methods exist with which to identify and quantify these components, and to correlate them to system health (i.e., system function and resilience), as well as how system health changes over time. Using functional groups to classify and distinguish between keystone components and redundant components is a viable methodology. Such an approach is useful to consider in the context of biocultural restoration of social-ecological systems, as data produced by this approach could be used to influence resource management policies. In accordance with systems theory, this approach could also be applied to other systems—both historical and modern.

However, as in ecology, there are no clearly defined thresholds used to classify components as either a keystone or a redundant, but rather a holistic view of the functional roles must be considered. While quantifying these metics provides insights into the importance of biocultural elements within a social-ecological system, there are no hard cut-off values, or even well-established guidelines, for interpreting data. Therefore, quantification alone cannot define either keystone or redundant components, but qualified assessments can help to illuminate such designations.

Through both quantitative and qualitative methods, we explored functional roles in the Hawaiian social-ecological system, and conclude that *kalo* qualifies as a keystone species for the Hawaiian culture, and further that *kalo* cultivation can be considered a keystone component of the Hawaiian social-ecological system. This suggests *kalo* and its cultivation is vital for the structure and function of the Hawaiian social-ecological system, and that the removal of *kalo* from parts of this system would result in either alternative regime states, or a regime shift resulting in an entirely new social-ecological system. Historical trends over the last two centuries support this notion.

#### *8.2. On Biocultural Diversity and Resilience in Social-Ecological Systems*

A loss of biocultural functional groups—due to a lack of both functional redundancy and functional diversity—could induce cascading extinctions on both sides of the social-ecological system. Therefore, increasing biocultural diversity is the most pragmatic way to manage resilience social-ecological systems. Redundancy within biocultural functional groups allows for resilience because of the presence of response diversity in such functional groups. In regions where a particular social-ecological keystone cannot exist, for whatever reason, redundancy in its biocultural functional group can facilitate the existence of an "alternative regime state" within the same social-ecological system, which is built around a successional keystone component. An "alternative regime state" is an altered stable state that is built upon a successional component of a biocultural functional group, one that would likely have a different level of resilience. Such a pehnomenon would also likely result in a cultural landscapes with a different outward appearance occurring within the same social-ecological system. The redundant compontents of Hawaiian agriculture

made for a resilient social-ecological system. However, a whole-scale removal of these components would theoretically induce a regime shift and result in an entirely new social-ecological system, and this has been historically observed in Hawai'i.
