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Predicting Prehistoric Taro (Colocasia esculentavar. antiquorum) Lo’i Distribution in Hawaii1
JOCELYN G. MÜLLER*,2, YELENA OGNEVA-HIMMELBERGER3, STEPHEN LLOYD
2,AND J. MICHAEL REED
2
2Biology Department, Tufts University, 163 Packard Ave., Medford, MA 02155-5818, USA3IDCE Department, Clark University, 950 Main St., Worcester, MA 01610, USA*Corresponding author; e-mail: [email protected]
Predicting Prehistoric Taro (Colocasia esculenta var. antiquorum) Lo’i Distribution in Hawaii.The artificial wetlands created through taro (Colocasia esculenta var. antiquorum) cultivationhave played an important but controversial role in discourse on Hawaiian culture, history, andnatural resource management. The extent of taro cultivation has risen and fallen dramaticallywith changes in population, trends, and culture since Hawaii was first settled by humans.However, since peak taro cultivation occurred before most historical records, it is unknownhow much artificial wetland was created in prehistoric times. Past estimates of the extent oftaro cultivation have been based on prehistoric population estimates, which are in themselveshighly contested. Here we present a simple model based on geographic and climate limita-tions to predict the maximum amount and distribution of land that could have been dedi-cated to taro production on the main Hawaiian Islands. Using geographic informationsystems technology, and historical records of taro distribution, we created a map of potentialprehistorical taro sites and total land cover. Our model predicts that prehistoric taro couldhave covered up to 12 times more land than suggested by past estimates. Limitations tothis model include the use of current geographic characteristics to predict historical land usepatterns and difficulties in creating parameters general enough to capture all sites withoutoverestimating taro cultivation. Despite these limitations, this model does well encompass-ing known prehistoric and historical taro localities and should serve as a basis for revisingestimated taro coverage.
Key Words: GIS modeling, Wetland, Polynesian agriculture, Pacific Islands.
IntroductionWetlands are focal points of many conservation
programs throughout the United States becauseof their key role in conserving biodiversity andsensitivity to urban growth (Dahl 1990). InHawaii, the wetland conservation discourse isfurther complicated by limited fresh water resour-ces, the growing water demands of both year-round and seasonal island inhabitants, and theimportant historical and cultural role played byagricultural wetlands, specifically taro (Colocasiaesculenta (L.) Schott. var. antiquorum) lo’i
(flooded field) agriculture (Stone and Stone1989; Walker and Hawaiian Waterbirds Recovery1977:93; Ziegler 2002).While taro is a common crop throughout
Polynesia, in Hawaii it plays a central culturalrole (Begley 1979:29; Greenwell 1947; Handy etal. 1972; Kirch 1985; Krauss 1993:5; Malo1951:320; Onwueme 1999). Presumably the firstPolynesian settlers in Hawaii carried the samevariety of crops found throughout Polynesiancultures today. But in Hawaii, they were facedwith very limited agricultural conditions, whichquickly made taro the most important crop(Begley 1979; Greenwell 1947; Wang 1983).Because of the age and volcanic origin of theislands, half of all the land cover was too high andsteep to be cultivated, and much of the rest of the
1 Received 24 June 2009; accepted 2 February2010; published online 5 March 2010.
Economic Botany, 64(1), 2010, pp. 22–33.© 2010, by The New York Botanical Garden Press, Bronx, NY 10458-5126 U.S.A.
land lacked the soft soil required for most crops(Jarves 1847:11; Newman 1970). These geo-graphic limitations meant that at the time ofPolynesian colonization, the arable land was almostexclusively associated with alluvial flood plains, thenatural habitat of taro. Thus, by exploiting naturalflood plains to create taro lo’i or irrigated patches,wetland taro agriculture became the central crop ofearly Hawaiians and an essential part of survival(O’Hair et al. 1982; Onwueme 1999). Today, taroimages and products are still sacred to Hawaiianculture (Winter 2006) and often are a componentof traditional celebrations (Begley 1979:29).
While wetland taro enabled early humanpopulation growth, the wants and needs of thepopulation surpassed the limits of production innatural wetlands, which pushed farmers toexpand floodplains and catchments. As theHawaiian culture became increasingly sociallystratified prior to European contact, there was adramatic expansion and intensification of tarocultivation (Handy et al. 1972; Kirch 2000).Kirch (2000) argues that this socioeconomicstructure both demanded and enabled great featsof hydraulic engineering, which underlie much ofthe wetland expansion. Furthermore, it was adramatic change in the socioeconomic structurethat triggered the decline of taro cultivation. Atthe time of peak taro cultivation, roughly aroundthe year 1650 C.E., the measures taken to createnew taro lands suggest that all optimal land wasunder cultivation (Kirch 2000; Kirch et al. 2004).However, the significant population decline andcultural restructuring that followed Europeancontact contributed to such a decline in taroproduction that by 1852 abandoned taro fieldsbecame sites of rice cultivation instead (Coulter1933:140; Krauss 1993:ix, 345). Since then, taroproduction has continued to decline, with onlyabout 80 ha currently in cultivation statewide(Nakamora 2005).
Surprisingly, despite many references to theexpansion of wetlands due to wet taro cultivation(Shallenberger 1977; Stone and Stone 1989:252;Walker and Hawaiian Waterbirds Recovery1977), we are unaware of any systematic attemptto estimate or map historical taro distributionsstatewide. There are, however, historical accountsthat describe and sometimes map historical tarolo’i distributions in individual valleys. The onlygeneral estimate we are aware of comes fromWalker et al., who estimated that at peakcultivation “the crop [taro] may have covered
twenty-five thousand acres [ten thousand ha]”(1977:2). Walker based this rough estimate onthe area that might support the caloric needs ofan estimated population of 300,000 Hawaiiansbefore European contact (R. Walker, pers. com.).These calculations were a guess made simply tofill a void in information and did not factor in thesocial hierarchy that pushed consumption beyondcaloric needs. Furthermore, this calculationhinges on an outdated estimate of pre-EuropeanHawaiian population. Although the estimates ofprehistoric Hawaiian populations have undergonemany revisions (Schmitt 1996; Stannard 1989),this value of taro cover has not been revised, butrather repeated in a number of documents relatedto endangered Hawaiian waterbirds (Griffin et al.1989). Our goal was to provide an alternativeestimate of maximum possible taro lo’i cover anddistribution on the main Hawaiian Islands:Kauai, Oahu, Molokai, Maui, and Hawaii, basedon the geologic and climatic conditions that limittaro. We used Geographic Information Systems(GIS) and a simple model of site suitability toestimate the potential maximum extent of artifi-cial wetland creation during the time of peak tarocultivation.
MethodsWe used reports of historical taro lo’i distribu-
tions to determine the climatic and physical limitsto taro cultivation to create a simple model forestimating the maximum possible extent of tarocultivation. Our analyses were based on historicaldocuments, missionaries’ accounts, and agricul-tural reports from as early as 1779, as well as onarchaeological information regarding prehistorictaro cultivation (e.g., Au Okou 1867; Kirch andKelly 1975; Newman 1970; Phelps 1937).Although these documents were all written afterthe presumed peak of taro agriculture, and archaeo-logical accounts are not exhaustive, together thedata were sufficient for model development. Thesedocuments also were used to evaluate the effective-ness of our resulting model. We assumed thatcultivated areas during the peak time for taroagriculture would include, but also go beyond, allhistorically-documented taro sites since taro culti-vation had already started to decline at the time ofthe earliest written accounts (Coulter 1931:33;Kirch and Sahlins 1992:2).
In order to calculate the historical taro landprior to contact, we created four Boolean mapsfor the four environmental constraints: slope,
23MULLER ET AL: PREHISTORIC TARO IN HAWAII2010]
distance to water source, rainfall, and elevation(Fig. 1). The final map of maximum tarodistribution was generated by overlapping all ofthe maps. This resulting map was then comparedto the historical maps of taro distribution.Described below are these parameters and the
basic procedure followed to get the final Booleanmap for each category.
ELEVATION
There is evidence of lo’i up to heights of 250 m(Handy et al. 1972) and 330 m (Kirch et al.
Fig. 1. The four Boolean maps shown separately for the island of Hawaii. The dark gray areas on the maps arewhere criteria are satisfied; light gray are where they are not. Map A is elevation; B is slope, C is precipitation; D iswater distance.
24 ECONOMIC BOTANY [VOL 64
2004) in very wet areas. Therefore, we generatedtwo separate elevational parameters (1–200 m and200–330 m), which had separate rainfall criteria(see below). Sites below 1 meter were excluded inorder to prevent confusion with coastal areas andfish ponds. Elevation data for the islands had apixel resolution of 30 meters, and came from theshuttle radar topography mission (SRTM, atwww.glcf.org). Data were downloaded in one-degree tiles in geographic coordinate system(using WGS84 datum). Tiles were then joinedby geographical coordinates using CONCATmodule in Idrisi Kilimanjaro software and thenreprojected into Universal Transversal Mercator(UTM-4N) coordinate system. Projection intoUTM was required for the subsequent slopecalculations. Finally, two separate Boolean mapswere created using RECLASS operation in IdrisiKilimanjaro GIS—one for elevations between 1–200 m, the other for the 200–330 m elevations.
SLOPE
Although terracing for taro lo’i was done, slopeappears to have been a limiting factor in wet tarocultivation. Based on distributional maps, weselected slopes of 2–35% to be acceptable fortaro. We chose the low end of this range becausewater needed to be flowing, and the upper endrecognizing the common practice of terracing(Handy et al. 1972). The values were based onquerying regions that were known to have taro andthose that were known to be excluded due to steepvalley sides. Using the final Digital ElevationModels for each island, we calculated slope inpercents since the reference units of UTMprojections are in meters and so are the value unitsfor elevation. From there we created a Booleanimage by assigning slopes between 2–35% a valueof 1 and all other slope values a value of 0.
DISTANCE TO WATER SOURCE
Wetland taro depends on adequate and pre-dictable running freshwater sources (streams,rivers, springs) that can be diverted for constantirrigation (Newman 1970). We set a distance of1 km from a perennial freshwater source as thelimit for water diversion, based on the width ofknown taro valleys. These widths were deter-mined by querying a distance to streams mapmade in Idrisi Kilimanjaro using the USGSDigital Line Graphs data (DLG, downloadedfrom www.usgs.gov). While this might appear
generous, it seemed appropriate because ancientHawaiians were able to divert water for greatdistances (Handy et al. 1972). Thus the modelmimics the upper limits of historical engineeringand is based on the assumption that slope andrainfall would restrict the result to a true projection.
After downloading the streams data (www.usgs.gov), we selected only streams listed as perennialbecause we concluded that streams not flowingyear-round would not be suitable for year-roundtaro agriculture. The one exception was on theisland Molokai. For this island, if only perennialstreams were used, the results did not matchother modern maps, which included streamsystems or other USGS data that we had of theisland, such as land-cover map from the NationalLand Cover Data (NLCD) set (http://landcover.usgs.gov/prodescription.php). We interpreted thisas indicating that the streams data were misclassi-fied and repeated the analysis on this islandincluding intermittent streams, which correctedmuch of the mismatch. Then we converted thevector line file of streams into a raster file. Usingthe BUFFER operation, we created a Booleanimage by assigning the area within 1,000 m ofperennial streams (perennial and intermittent oncase of Molokai) a value of one. The streamsthemselves obtain a value of zero, as does the areaoutside the threshold distance.
RAINFALL
The amount of rainfall required for tarocultivation was the most difficult to simplifybecause it depended on the age of the islandand soil permeability (Newman 1972). Specifi-cally, on younger islands, such as the island ofHawaii, soil is more permeable and hence lesssuitable for lo’i. Only heavily-exposed areas wouldhave weathered sufficiently to have some waterretention, so the threshold between sufficient andinsufficient rainfall on a younger island wouldtherefore have to be significantly higher for sitesto remain inundated (Newman 1972:559–600).On older islands, however, there is greatererosion, even in regions with less exposure torainfall. There would be soil differences within anisland, with points of higher elevation having lesscumulative water, being less weathered, andrequiring a higher rainfall threshold. By queryingour rainfall images for the valleys that we knewsupported taro historically, we arrived at a lowerthreshold of 650 mm rain on all islands except
25MULLER ET AL: PREHISTORIC TARO IN HAWAII2010]
the island of Hawaii. For these same islands, sitesabove 200 m were considered suitable if theyreceived 800 mm or more of annual rainfall. Forthe Hawaii Island, the cut-off island-wide was1,200 mm annual rainfall, and this was used forall elevations. We assumed there would be noupper limit to the amount of rainfall above whichtaro could not be grown.After downloading from the State of Hawaii
governmental website contours showing rainfallin millimeters per year, the line data wererasterized and interpolated using the topo toraster tool in ArcMap to create a continuoussurface. When doing this, we made sure to matchthe extent and resolution of the output surfacewith those of the particular island’s elevationimage in Idrisi. Then the image was reclassified sothat only the area that was above the thresholdlevel of rainfall for the particular island was givena value of one, and everything else a value of zero.Our final step in creating a map of possible
maximum historical distribution was to combinethe four Boolean images using the OVERLAY(multiply) operation in GIS to find the areaswhere all four constraints were satisfied. We thenconducted a sensitivity analysis to ensure that allfour criteria were in fact contributing to themodel and to uncover any correlations betweenthe criteria. This process was repeated for all fiveislands.
ResultsThe sensitivity analysis revealed that all four of
the criteria were necessary for the model (Table 1).None of the criteria were correlated with oneanother across the five islands, nor did any onecriterion seem to represent the majority of thefinal model. Our model predicted the maximum
possible taro lo’i coverage to be 121,100.5 ha forthe combined total for all islands, with Kauai andOahu contributing the most to the total coverage(Fig. 2). From 240 documented taro-producingvalleys, the area represented by our projectedmaps (Fig. 3) fully included 165 of them, whichis a 69% success rate, with another 24 valleyspartially included, giving a total of 79% overlap(Table 2).
DiscussionThe only published estimate of taro coverage of
which we are aware was by Walker et al. (1977),who suggested that there might have been
TABLE 1. A TABLE OF THE SENSITIVITY OF THE MODEL TO EACH OF THE FOUR COMPONENTS: ELEVATION, SLOPE,RAINFALL, AND DISTANCE FROM WATER SOURCE. FOR EACH OF THE FOUR CRITERIA, THERE IS THE TOTAL LAND AREA
(IN SQUARE KM) THAT MEETS THOSE CRITERIA ON EACH OF THE ISLANDS AND THE PERCENTAGE OF THAT AREA
INCLUDED IN THE FINAL MODEL.
Hawaii Island Kauai Maui Molokai Oahu
Area, sq.km % Area, sq.km % Area, sq.km % Area, sq.km % Area, sq.km %
Elevation 2,111 12 858 53 932 15 439 4 1,152 29Slope 10,113 3 931 49 1,550 9 482 4 1,076 31Rainfall 6,422 4 1,286 36 1,387 10 324 6 1,323 25Water-distance
1,371 19 1,090 42 516 28 154 12 715 47
Final map 262 458 142 18 335
Predicted Maximum WetlandTaro Cultivation by Island
Kauai Oahu Hawaii Maui Molokai0
10000
20000
30000
40000
50000
Island
Pre
dic
ted
Are
a (H
a)
Fig. 2. Predicted maximum coverage for total pre-historic taro lo’i by island, within the restraints ofless than 330 m above sea level, rainfall 650 mm/yr(800 mm for higher elevations, 1,200 mm for theHawaii Island), 35% slope, and less than 1 km froma perennial water source. The calculations were madeusing Boolean analysis in Idrisi Kilimanjaro program.Our model predicted that wetland taro could havecovered 121,100.5 ha on the five main Hawaiianislands at the time of peak cultivation.
26 ECONOMIC BOTANY [VOL 64
10,000 ha of taro lo’i at its peak in Hawaii.Without producing maps that greatly contradictknown taro localities, our model predicts apossible maximum coverage over twelve timesWalker et al.’s estimate (Fig. 1). Although thisestimate is dramatically different, we wouldexpect the previous estimate to be low because it
started with a low estimate of pre-EuropeanHawaiian population size and was not revised tomatch updated estimates of those populations(Stannard 1989). Furthermore, the calculation ofWalker et al. (1977) did not account for thesociocultural factors involved in taro production(e.g., taxation, ritualistic use, and patronage)
Hawai’i
Maui
A: Oahu
B:
C: Molokai
D:
E:
Kaua’i
Fig. 3. Map of GIS model results for the five largest islands of Hawaii: A) Oahu, B) Maui, C) Molokai, D)Kaua’i, and E) Hawaii. Documented taro-producing areas are numbered by island and can be referenced inTable 2.
27MULLER ET AL: PREHISTORIC TARO IN HAWAII2010]
(Kirch et al. 2004; Malo 1951:207), and theywere never intended as a serious estimate ofstatewide taro coverage (R. Walker, pers. comm.).We do not presume that our estimate is an
accurate reflection of how much taro was actuallygrown in Hawaii. Rather, we intend it to be anestimate of the maximum possible coverage, and toact as a starting point for further refinement. Ourresults indicate that this simple model does a fairlygood job of describing the known patterns of histor-ical taro-producing valleys. For example, historicalaccounts describe the two largest taro-producingislands as Kauai and Oahu (Begley 1979:29; Handyet al. 1972:488; Kirch 2000:5). Our model alsopredicts that these islands have the greatestpotential cover of lo’i. We must be cautious inthe interpretation of these data. Inherent errors inthe GIS predictions are expected because we areusing modern geographical data to predict historicalpatterns. However, despite the inherent problemsusing modern data to predict the past, the modelstill does well in predicting most of the historicalvalleys and well-known patterns.Inspection of our proposed maps suggests that
our model might be a conservative estimate ofpossible historical taro lo’i coverage. Whencompared to historical records, there are isolatedvalleys, as well as larger regions, not representedby our model. There seem to be two factors thatcontribute to these mismatches: rainfall andstreams. Taro, as an irrigated crop, is not strictlydependent on rainfall but on a supply of freshrunning water. However, freshwater is the mostdifficult parameter to determine, as it is depend-ent on soil type, rainfall, and island age. OnKauai, for example, modeled potential tarogrowth along the coastal portion of the Pakalavalley is restricted due to rainfall criteria, whereasthe upper elevations were included. Logically, ifthe upper elevations were receiving enough rain,then water would contribute to fields below andallow for taro cultivation.So, although the rainfall parameters used for
the model allowed us to recreate broad patterns,the model might be improved by using moredetailed soil and run-off data in place of the broadrainfall constraints. This would also allow fordownward slope accumulation to replace a basicdistance from water source as the measure forhydraulic engineering possibilities. The secondfactor that seems to contribute to certain valleysnot being represented in our model, even thoughthere is known historical taro production, was the
presence or absence of perennial streams. Againthe choice of perennial streams was made toensure that this would represent permanent taroaquaculture; however, it must be recognized thatwe were using modern information to classifyperennial streams. It is well documented that thelocation and water-flow of many streams has beenaltered with increasing development of theislands. Many regions have been drained, theirstreams diverted and springs capped (Handy et al.1972; Smith et al. 1990). This means that valleysthat were once taro-producing may no longerseem suitable according to modern stream data.An example of this on the island of Kauai is theMana region (Fig. 3D, #44). This region used tobe a taro-producing area, but it was drained forsugar production in the last century and now hasvery few water sources that are accounted for ingeographical surveys of natural landscape features.In a few regions, however, the modern changes ofwaterways are not enough to explain the mis-match between the model and documentedhistorical sites. For example, on Molakai, theUSGS streams data listed no perennial streams onthe western 80% of the island (Fig. 3C). How-ever, modern vegetation maps indicate that theentire western half of the island is considered wetor moist, and even most road maps will docu-ment rivers such as Pelekulu (Fig. 3C, #4) asperennial (e.g., DeLorme 1999). On Molokai,since the unmatched region was so large, themismatch was corrected for by including inter-mittent streams in the analysis. However, thislack of accurate waterway data is still an issue in afew other regions.So while in some regions our maps appear to
be conservative estimates of prehistoric tarocoverage, this coverage should not be interpretedas representing total usable agricultural wetland.To know the true extent of artificial wetland, wewould also have to account for other factors suchas the amount of our predicted taro habitat thatwas actually human settlements and infrastruc-ture, fallow land, etc. For example, in the easternregion of Kauai (Fig. 3D, #26–35), this vastexpanse of continuous fields, while reasonablebased on the geographic nature of the land, wouldbe difficult to manage if it were not interruptedby settlements to house the taro farmers. Even insmaller regions such as the northern region ofHawaii, the wide valleys (Fig. 4) would most likelyhave been subdivided into fallow and active fields,paths, housing support, possibly even fish ponds.
28 ECONOMIC BOTANY [VOL 64
TABLE2.
ALIST
OFALL
DOCUMENTED
TARO-PRODUCIN
GVALL
EYSBYISLA
ND.F
OR
EACH
AREA
WE
LIST
THENAME,K
EY(R
EFE
RENCETOFI
G.3
),AND
SCORE(Q
UALITATIVE
MATCH
BETWEEN
MODEL
AND
REFE
RENCE).BASE
DON
THE
QUALITATIVE
DESC
RIPTIO
NOF
TARO
LANDSAND
THE
GRAPH
ICAL
MODEL
RESU
LTS,
WE
ASSIG
NED
APO
SITIVE
MATCH(+)TO
AREASWHERETHEMODELPR
EDIC
TSWETLA
ND
TARO
INTHESA
MELO
CATIO
N,S
IZE,A
ND
SCOPE
ASDESC
RIBED
INHISTORIC
ALDOCUMENTS.AN
INTERMEDIATE
SCORE(0)MATCHESONLY
INLO
CATIO
NBUT
NOT
SIZE
OR
SCOPE,W
HEREASA
NEGATIVE
SCORE(−)IN
DIC
ATESTHE
MODEL
AND
LITERATURE
DO
NOT
MATCH(A
UO
KOU
1867
;KIRCH
ANDKELL
Y1975;N
EWMAN1970
;PH
ELP
S1937).
Locatio
nScore
Key
Locatio
nScore
Key
Locatio
nScore
Key
Locatio
nScore
Key
Manaw
ainu
igulch
–C1
Miloli’i
0D1
Kahaha
0B9
Waialua
+A9
Waihanau
–C2
Nu’ulolo
+D2
Honokahua
+B10
Helem
anoStr.
+A10
Waikolu
–C3
Awa’aw
apuh
i+
D3
Honolua
0B11
Kaw
ailoa
+A11
Pelekunu
–C4
Honopu
+D4
Honokohau
+B12
Waimea
+A12
Wailau
–C5
Kalalau
Valley
+D5
Anakaluahini
–B13
Waiale’e
–A13
Kahaw
ai’iki
–C6
Hanakoa
+D6
Poelua
–B14
Kaw
ela
+A14
Halaw
a+
C7
Waiahuakua
+D7
Honanana
–B15
Kahuku
+A15
Kam
anoni
0C8
Hanakapi'ai
+D8
Waihali
+B16
Malaekahana
+A16
Pohakupu
li+
C9
Limahuli
+D9
Kahakuloa
+B17
Keana
–A17
Honouliw
ai0
C10
Ha’ena
+D10
Wailena
+B18
La’ie
+A18
Moanu
i+
C11
Manoa
+D10
Waiolai
+B19
Kaloa
+A19
Waialua
+C12
Wainiha
+D11
Makam
akaole
0B20
Hau’ula
+A20
Poniuahu
a+
C13
Lumahai
+D12
Waihe’e
+B21
Kaluanu
i+
A21
Puelelu
+C14
Wai’oli
+D13
Waiehu
+B22
Kaliuwa’a
+A21
Kaw
aikapu
+C15
Hanalei
+D14
Wailuku
+B23
Punalu’u
+A23
Honom
uni
+C16
Kalihi-k
ai+
D15
Ioa
+B23
Kahana
+A24
Puko’o
+C17
Kalihi-w
ai+
D16
Waikapu
0B24
Kaw
a+
A24
Mapulehu
–C18
Kilauea
+D17
Ukumeham
e0
B26
Kalehua
+A24
Kuliula
+C19
Pila’a
–D18
Maliko
–B27
Koloahu
lu+
A24
Ualapu’e
–C20
Waiakalua-nui
0D18
Kuiaha
+B28
Pilali
+A24
Kahananui
0C21
Waiakalua-ik
i–
D19
Ho’olaw
anui
+B29
Ka’a’aw
a+
A25
Ka’am
ola
–C22
Waipake
0D20
Waipio
+B30
Hakipu`u
+A25
.5Keawanui
+C23
Lepeuli
+D21
Hanehoi
+B31
Waikane
+A27
Kam
aloeastward
+C24
Maloa’aStream
D22
Hoalua
+B32
Waiahole
+A28
Palicoast
+C25
Papa’a
–D23
Kailua
+B33
Keahu
espring
+A28
WaiakaStr.
–E1
Aliomanu
–D24
Na’ili’ilihaele
+B34
Pu’u
Kahea
+A29
Kaw
aihae
–E2
Anaholariver
+D25
Waikamoi
+B35
Waihe’e
+A30
Akamoa
+E3
Kealia
+D26
Puohokam
oa+
B36
Ka’alaea
+A31
29MULLER ET AL: PREHISTORIC TARO IN HAWAII2010]
Wainaea
+E4
Kapa’a
+D27
Haipu
ena
+B37
Kahalu’u
+A32
Halaw
a+
E5
Waipouli
+D28
Honom
anu
0B38
He’eia
+A33
Walaohia
+E6
Kaw
i+
D28
Nu’uailua
+B39
Kaw
a+
A34
Puwa’I’ole
+E7
Keahu
a+
D28
Ke’anae
+B40
Kane’ohe
+A35
Niuli’i
+E8
Iole
+D28
Waianustr.
+B41
Kaw
ainu
iMarsh
+A36
Waikama
+E9
Wailua
+D29
Wailua-nu
i+
B42
Kailua
+A37
Waiapuka
–E10
Waikoko
+D30
W.Wailua-iki
+B43
Waimanalo
+A38
Pololu
+E11
WailuaFalls
+D31
EastWailuaiki
+B44
Kuli’ou’ou
–A39
Honokane-nu
i+
E12
Iliiliula
+D32
Kapili’ula
+B45
Niu
+A40
Waimanu
+E13
Waiaka
+D32
Waiohue
+B46
Wailupe
–A41
Waipio
+E14
Waiahi
+D32
Hanaw
i+
B47
Wai’alae
+A42
Hi’ilawe
0E15
Kaulu
+D32
Nahiku
+B48
Palolo
+A43
Kukuihaele
+E16
Palikea
+D32
Opae-ku’i
–B49
Honolulu
–A44
WaikoloaStr.
–E17
Halii
+D32
Koali
–B50
Manoa
+A44
Laup
ahoehoe
+E19
Hanam
aulu
+D33
Wailua
–B51
Pauoa
+A45
Maulua
+E20
Pualistr.
+D34
Palikea
str
+B52
Nu’uanu
+A46
Hakalau
+E21
Naw
iliwili
Bay
+D35
Lolokea
+B53
Waikiki
–A46
Wailea
+E22
Mahaulepu
–D36
Alelele
+B54
Waolani
+A47
Honom
u+
E23
Koloa
+D37
Kalepa
+B55
Kapalam
a+
A48
Kaw
ainu
i+
E24
LawaiStr.
+D38
Nu’anu’aloa
+B56
Kalihi
+A49
Aalakahi
+E25
Wahiawa
+D39
Kahikinui
+B58
Moanalua
+A50
Pahoehoe
+E26
Weliweli
+D40
O’opu
olaGulch
–B59
Kalou
str.
+A50
Kapehu
+E28
Hanapepe
+D41
S.of
Ham
oa+
B60
Halaw
astr
+A51
Waiakea
Bay
+E29
Waimea
∼D42
Haleakala
0B61
Manana
+A52
Waiohinu
–E30
Kekaha
+D43
Kula
+B62
Waimano
0A53
Punalu’u
–E30
Mana(m
arshland
)–
D44
Honua’ula
+B63
Waiaw
a+
A54
Leew
ard
–E30
Wai’eli
+D44
Wahiawa
+A1
Waipahu
–A55
Kau
–E30
Olowalu
0B1
Wai’anae
–A2
Ewadistrict
0A56
North
Kohala
0E31
Laun
uipiko
+B2
Kaukonahu
aV.
+A3
Pu’uloa
–A57
Ham
akua
coast
+E32
Kaua’ulaGulch
–B3
Makaha
+A4
Waikelestr.
+A59
wwdMauna
Kea
0E32
Kahom
a0
B4
Helem
anoStr.
+A5
Waipio
–A60
Puna
toHilo
–E33
Lahaina
–B5
Uluhu
lu–
A6
Poam
ohoStr.
–A61
wwdMauna
loa
0E33
Kanaha
0B6
Kaw
aihapai
+A7
Waianustr.
+A62
wwdKohala
+E34
Honokaw
ai–
B8
Mokule’ia
+A8
Waimalu
+A63
30 ECONOMIC BOTANY [VOL 64
Based on archaeological sites (Kirch 1985; Kirchand Kelly 1975), a rough estimate of the amountof land devoted to settlement and infrastructurein taro-producing valleys suggests a 25% reduc-tion in wetland coverage from total suitable land.Furthermore, qualitative descriptions of somevalleys lead us to believe that the actual coverageof taro may be overestimated by our maps. Forexample, Handy et al. (1972:424) describeWaipouli valley as containing an insignificantamount of wetland taro, whereas our modelpredicts this valley to be suitable for taro lo’i.Keeping these limitations in mind, however, thisis a simple model that predicts the patterns ofhistorical taro cultivation fairly well. It providesthe first attempt of which we are aware to plot thepotential extent of taro lo’i production across theHawaiian Islands.
ConclusionsOur model uses simple geographical and
climatic features to predict the maximum extantof wetland taro agriculture in prehistoric Hawaii.
The model estimates total wetland taro coverageat 121,100 ha over the five islands examined.Including estimates of the infrastructure ofhuman populations would reduce this figure by25%, to 90,825 ha. This still increases previousestimates of wetland taro coverage by almostninefold, and this extent supports recent upwardrevisions of estimates of prehistoric populations ofboth humans and wetland flora and fauna. Wehope that this paper will serve as a base for furtherexploration in the use of GIS in predictingprehistoric land use in Hawaii.
AcknowledgmentsWe thank Nancy Hoffman and Mike Silber-
nagle (U.S. Fish and Wildlife Service) for theirassistance in reviewing the draft manuscripts andfor valuable discussion on the current state ofknowledge on Hawaiian bird ecology; RonNakamora (Hawaiian Agriculture Statistics Serv-ice) for sharing the taro and current agriculturestatistics; Arleone Dibben-Young for her help inplacing Molokai references; Kawika Winter
Fig. 4. Map of the northern windward side of Hawaii Island. Areas predicted to be covered in historical taro aredepicted in gray.
31MULLER ET AL: PREHISTORIC TARO IN HAWAII2010]
(Limahuli Garden and Preserve Kaua’i) for thehelpful review and ground-truthing of earlierdrafts of the model; and Aissatou Noma for helpwith map creation.
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