Spatial patterns of seasonal crop production suggest coordination within and across dryland agricultural systems of Hawaiʻi Island

Abstract

ABSTRACT. Hawaiian dryland agriculture is believed to have played an important role in the rise of archaic states and consolidation of political power. At the same time, the sensitivity of agricultural production in dryland field systems to temporal variability in climate would have had implications for economic and political relationships, both competitive and cooperative. In this study, we explore whether and how annual cycles of climate might have constrained seasonal cultivation and crop production in three rain-fed field systems on the Island of Hawaiʻi. We utilized a recently developed monthly gridded climate dataset for the Hawaiian Islands to compare the Kohala, Kona, and Kaʻū field systems in terms of mean annual climate and seasonality. We found that despite superficial similarities in elevation and annual rainfall, the field systems differ in climatic variables associated with evaporative water loss and in the timing of the rainy season. Aridity, a ratio of evaporative demand to rainfall, is strongly seasonal for Kohala and Kaʻū relative to Kona. When we imposed temperature and moisture criteria to visualize seasonal cultivation envelopes defined for sweet potato (Ipomea batatas), we found strong spatial patterns associated with the onset and length of the growing season, and these suggest seasonal complementarity in crop production within and between field systems. This complementarity indicates coordination both within and between field systems through consolidation, coercion, or increased cooperation could have alleviated periodic food stress and contributed to more stable political hierarchies, which may explain similarities in their respective chronologies of development. We suggest that our approach for characterizing seasonal constraints to dryland cultivation provides a useful tool for advancing continued restoration and research in these and other rain-fed dryland systems across Hawaiʻi and the tropics.

Anthropocene Dynamics in the Prehistoric Pacific

“…Accordingly, while traditional wetland and pondfield horti culture in Kaua'i, O'ahu, and Moloka'i seems to have supported population growth and the formation of stratified chiefly societies, it is the massive dryfield agroeconomies of Hawai'i and Maui that pushed Hawaiian society toward degrees of complexity otherwise unattested in the Pacific (Kirch 2018). The infrastructural specifics of these field systems were minutely finessed, responsive to local environmental specifics, to drive intensive horticultural production over large areas (e.g., Kagawa-Viviani et al 2018). The scale, intensity, and degree of integration of these systems, and not the wetland systems of the windward coast, seems causally implicated in the emergence of managerial and land-owning class structures incorporated into large, territorially coherent polities (DiNapoli and Morrison 2017b; Kirch 2010;Ladefoged et al 2008).…”

Restoration of ‘Āina Malo‘o on Hawai‘i Island: Expanding Biocultural Relationships

“…In contrast, agriculture practiced on dry lands is presented as having less infrastructural development and higher labor costs, resulting in lower surplus production and, therefore, higher vulnerability to social disturbances [17]. Such systems, being dominantly rainfed, are also inherently more variable in their production, both spatially and temporally; therefore agriculture on 'āina malo'o has been considered more vulnerable to natural disturbances as well [12]. However, these generalizations are built upon sparse investigations into traditional agricultural systems, and none of them on operational systems in Hawai'i.…”

“…These continuous systems occupied vast areas on the younger islands; the largest of which was likely the Ka'ū system that may have covered over 50,000 acres [11,19]. Portions of these systems were likely farmed seasonally based on patterns of rainfall and temperature [12,13]. Agroforestry and other forms of tree agriculture represented another significant fraction of agriculture on 'āina malo'o ( Figure 3).…”

“…What we now see as the archaeological infrastructure is only the remaining physical manifestation of the diverse practices and cropping systems employed within the sites. A simple comparison of the sites themselves offers a case-study of adaptation, with vastly different forms consisting of different suites of crops, temporal patterns, and practices seen (e.g., References [8,10,12,14,18,97]). One thing that has been clear in the restoration of these systems is the diverse and innovative methods for managing water.…”

“…Before European contact, Native Hawaiian agriculture was highly adapted to place and expressed a myriad of forms [7]. The development of unique resource management practices evolved to local environments maximized efficient productivity [8][9][10][11][12][13][14]. This led to highly specific, place-adapted indigenous knowledge that powered the political evolution of the ancient Hawaiian state.…”