My interest in traditional agriculture builds on a body of Pacific Island archaeology that has looked at the relationship between environment and political economy through contrasting chiefdoms centered on irrigated “wet” and rain-fed “dry” agricultural systems. The Hawaiian Islands exemplify this dichotomy, thus syntheses of historical trends have been primarily based upon a few key settlement pattern studies on windward valleys and leeward field systems.
The Kalaupapa Field SysteM, Moloka‘i Island
Recent research has concentrated on the dry type of agricultural system, especially the Kohala and Kona Field Systems in leeward west Hawai'i Island as well as leeward locations that lack formal field systems.
Location of the Kalaupapa Field System, Moloka‘i Island.
An air photograph derived map of stone field boundary walls visible Kalaupapa Field System.
In Kalaupapa we find a rare example of an intensive dryland system located in a wet, windward environment that allows one to examine the historical associations between environment, agriculture, and social development in Hawaiian prehistory.
Examples of stone field boundary walls.
The Kalaupapa Field System is a nine km2 grid of rain-fed plots defined by low stone field walls built to shelter low growing crops like sweet potatoes from the constant northeast tradewinds.
Map of relative wind strength.
By making a series of observations on wind caused plant deformation, like the small shrubs shown above growing in the lee of field walls, this detailed map of wind strength was created as a first step toward evaluating the impact intensive agriculture on local rates of soil erosion.
Agricultural soil sampling within a field plot.
Next, soil samples were taken from two different kinds of context –control samples from under field walls that pre-dated intensive agriculture and samples from the center of plots that post-dated intensive agriculture.
A comparison between levels of phosphorous in soil before and after intensive agriculture. Note decreased levels near the windward coast and increased levels further away from the coast.
Chart of the changes in the scale of wind erosion after intensive agriculture.
Finally, through collaborative effort with soil scientists at the University of California, Santa Barbara, soil nutrient analysis was employed to track increased wind erosion that caused depletion where winds were strongest as well as downwind enrichment of soils. Overall, it appears that despite the construction of hundreds of windbreaks that wind erosion increased with intensive cultivation of the peninsula.