27

Excavation of Pit-Agriculture Landscape on Majuro Atoll,
Marshall Islands, and Its Implications
Toru YAMAGUCHI,1 Hajime KAYANNE,2 Hiroya YAMANO,3 Yayoi NAJIMA,1
Masashi CHIKAMORI,4 Hiromune YOKOKI5
1

Department of Ethnology and Archaeology, Keio University,
2-15-45 Mita, Minato-ku, Tokyo 108-8345, Japane-mail: toru38@flet.keio.ac.jp
2
Department of Earth and Planetary Science, The University of Tokyo,
3-7-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
3
Social and Environmental Systems Division, National Institute for Environmental Studies,
16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
4
Faculty of Informatics, Teikyo Heisei University,
2289-23 Uruido-Otani, Ichihara, Chiba 290-0171, Japan
5
Center for Water Environment Studies, Ibaraki University,
4-12-1 Nakanarusawa, Hitachi, Ibaraki 316-8511, Japan

Abstract
Coral atolls have been considered the most precarious landforms thus having an extremely severe
environment for human settlements in the Oceanic realm. It appears that atoll islets of foraminiferal
sand and coral shingle accumulated on reef flats are considerably weaker than high islands with regard
to sea-level change and climatic fluctuation, but there also seems to be variety to their vulnerability. Infact our excavation on Laura, the largest and widest islet in Majuro atoll, Marshall Islands, has revealed
that its earliest colonization surprisingly dated back to 2,000 BP, and agricultural pits for cultivation ofaroid species – probably Cyrtosperma – were constructed some centuries later at the least, while asmaller islet shows a much younger age of 360 BP. The long-lasting landscape of pit agriculture comprising remarkable undulation and rich vegetation, which appears to be the richest and most diverse partof the present atoll environment, can be viewed as a symbol indicating the islets are in good condition in
aspects of both land formation and human subsistence. Here, we will discuss this landscape as a historical product invented through the entanglement between two agencies, nature and human. Understanding
this will be also helpful in framing policies regarding anticipated sea-level rising in the future.
Key words: archaeological excavation, Oceanic atolls, pit agriculture, prehistoric human settlements

1. Introduction
In the trade wind zone are scattered a number ofcoral atolls, the most precarious landforms of the central Pacific realm. Their islets of foraminiferal sandand coral shingle accumulated on reef flats are often
no more than 2-3 meters in elevation and a few hundred meters wide. A storm surge easily inundates such
low and flat islets. There is no running surface water
either, and thus some atolls frequently suffer fromdroughts. The atoll environment appears to be extremely severe for any human settlement.
Near the center of larger islets, however, exist
remarkable banks that are several meters higher than
the surrounding flat and low surface. There are now
houses or graveyards on these banks. Each of them
Global Environmental Research9(1)/2005: 27-36
printed in Japanencircles an agricultural pit dug into the water tableof the freshwater lens. The pit is infilled with soils
containing much humus which have been developedby the deliberate addition of vegetable compost to
provide a nutrient-rich layer. Colocasia and/or
Cyrtosperma tubers, the latter prevailing in the Eastern Micronesia, are planted in this wet ground (Fig.1).
When Cyrtosperma is fully grown, it measuresmore than 3 meters in height and produces tubers
weighing 20-30 kg. While it takes 9 months to a few
years to harvest the tubers, they have the highest
carbohydrate content per unit among the aroid tubers.
Cyrtosperma also withstands a high level of water oreven flooding, provided that it does not result in an
inflow of sea water. The species is thus more adaptable to a water table fluctuating with tidal change©2005 AIRIES28

T. YAMAGUCHI et al.

(Lambert, 1982). This characteristics may be one reason Cyrtosperma is the main aroid grown in the atollsof Micronesia.
Tall trees of Chinese lantern (Hernandia sonora),
Pacific rosewood (Cordia subcordata) and fish-poison
tree (Barringtonia speciosa), as well as coconut andbreadfruit trees, grow on the banks of the
Cyrtosperma pits and shade the inside of the pits so as
to prevent the moisture of the hydromorphic terrain
from evaporating. These elements appear to provide
the richest landscape, as a whole, in contrast with theprevailing image of atoll environments. However, thelandscape has just begun to be scrutinized as a historical product (e.g., Weisler, 1999a). The present article
is thus intended to examine what agencies invented
the landscape of agricultural pits on the basis ofarchaeological evidence from our excavation in 2003
on Laura islet in Majuro Atoll, the Marshall Islands.

2. Excavation of Laura, Majuro Atoll
Micronesia encompasses about 2,100 islands, mostof which lie between the equator and 20 degrees N
latitude. The Marshall Islands, lying along its eastern
margin, consists of 29 atolls and five small coralislands, which are spread over approximately 2 million km2 of ocean (Fig.2). These islands come in two,nearly parallel chains: the Ralik (sunset) group in thewest and the Ratak (sunrise) group in the east. They
are aligned in a NW-SE direction and extend over a
distance of nearly 1,200 km between 4 to 12 degrees
N latitude, and also form substantial links in a
scarcely broken chain of island groups along with
Kiribati and Tuvalu Islands.
Majuro Atoll is situated at 7 degrees N latitude and
171 degrees E longitude, in the southern part of the
Marshall Islands (Fig.3). This atoll consists of morethan 60 islets on reef flats encircling a large lagoon

Fig. 1 Cyrtosperma agricultural pit (a) and its spoil bank (b) in Laura, Majuro Atoll.

Fig. 2 Map of Eastern Micronesia and estimated colonization routes to the Marshall Islands.

Excavation of Pit-Agriculture Landscape on Majuro Atoll, Marshall Islands, and Its Implications

measuring 41 km by 11 km with the long axis extending east to west. The total land area is just less than
10 km2. The Marshall Government organizations areallocated on its eastern islets, named Djarrit, Uliga
and Delap, at present.
Majuro is the first atoll in the Marshall Islands tohave been systematically excavated by the archaeologists of the Bishop Museum, who not only collected
plenty of artefacts, adding up to 4,122, but also reported the first evidence of human settlement on atolls
ca. 2,000 BP, which was excavated from Laura, thewesternmost islet of Majuro (Riley, 1987). Our fieldresearch in 2002 and 2003 also focused on this islet.
Passing westward from the eastern islets through thelong and narrow islet of Long Island, one arrives atLaura with a land area of 1.2 km2. This islet is crescentic in shape, measuring approximately 1,200 m at
the widest point between shorelines, lagoonward andoceanward (Fig.4).
Two transect lines were selected in the vicinity ofwidest point, one in each research year, to survey the
topographic profile: MJ-Lr1 in 2002 and MJ-Lr-2
mainly in 2003. For archaeological and geomorphological purposes, ten sites were excavated along
these lines, of which, a site lying at the center of Laura(MJ-Lr2-8) is the focus of our examination here. This
site is on a heap located between two Cyrtosperma
agricultural pits (Fig.5). The top is 261 cm high above
the present mean sea level and the bottom of the pits,
28 cm. It appears to be a remarkable undulation incomparison with the general landform of low, flat
islets (Fig.6). A two by four meter trench was excavated to an approximate depth of 150 cm and intact
stratified deposits were encountered there, whichcame roughly in three strata excluding the surface
humus as follows (Fig.7):

Fig. 3 Majuro Atoll in the Marshall Islands and location of Laura Islet.

Fig. 4 Excavated sites on Laura Islet.

29

Fig. 5 Location of sites MJ-Lr2-8 and 2-3.

30

T. YAMAGUCHI et al.

(i) the lowest stratum (Layer 7) contains very pale
brown sand (Mansell’s color, 10YR7/3) that is
almost horizontally accumulated, and thus shouldbe the natural sediment. Its skeletal components
consist of sand-size fragments of coral, coralline

algae, mollusks and abundant tests of foraminifera.
The samples were collected from the same stratum at site MJ-Lr2-3 lying at the foot of heap,
from which two ages of 2,380 BP were obtained(Table 1);

Fig. 6 Undulation of pit agriculture at site MJ-Lr2-8.

Fig. 7 Stratigraphy of site MJ-Lr2-8.

Table 1 Radiocarbon ages (AMS) from sites MJ-Lr2-8 and 2-3.
Lab. CodeMaterial

Provenance(Site, Layer or Feature)

Layer 3 (upper) at MJ-Lr2-3,
equivalent to 1st Stratum,
Layer 7 at MJ-Lr2-8
Layer 3 (lower) at MJ-Lr2-3,
Beta-191714
foraminifera
equivalent to 1st Stratum,(AMS)(Calcarina spp.)
Layer 7 at MJ-Lr2-8
PLD-2790
wooden charcoal
2nd Stratum, Unit 1 / Feature 6(AMS)(monocoty ledon)(Eastern section profile)
PLD-2785
wooden charcoal
3rd Stratum, Unit 2 / Feature 0(AMS)(Cordia spp.)(Eastern section profile)
PLD-2786
wooden charcoal
3rd Stratum, Layer 4(AMS)(Pandanus spp.)(Western section profile)
PLD-2787
wooden charcoal
3rd Stratum, Unit 1 / Feature 3(AMS)(Cocos spp.)(Western section profile)
PLD-2788
charred phalange of 3rd Stratum, Unit 1 / Feature 4(AMS)
fruit (Pandanus spp.)(Western section profile)
PLD-2789
wooden charcoal
3rd Stratum, Unit 1 / Feature 5(AMS)(Cordia spp.)(Eastern section profile)Beta-191711
(AMS)

δ13C
(‰)

foraminifera(Calcarina spp.)

14

C age
(yrBP±1σ)Cal. Year (1σ)

2,380±40
2,380±40−27.8

2,010±50

cal. BC 50 - cal. AD 60 (99.4%)−25.8

1,850±45cal. AD 125 - 235 (97.0%)−28.1

1,755±45cal. AD 230 - 345 (94.6%)−26.3

1,825±45cal. AD 130 - 240 (100%)−25.4

1,720±45cal. AD 255 - 300 (41.4%)
cal. AD 320 - 385 (58.6%)−25.7

1,770±50

cal. AD 215 - 340 (91.9%)

Excavation of Pit-Agriculture Landscape on Majuro Atoll, Marshall Islands, and Its Implications(ii) the second stratum (Layer 6), lying just on top of
the natural stratum, contains dark gray sand
(10YR4/1) and charcoal flecks. It appears to be
the earliest buried A horizon. From a shallow pitof an earth oven (U.1-Fe.6) on the eastern profile,a lot of burned coral pebbles and charred flecks ofprobable monocotyledon trunk and coconut endocarp were retrieved, which dated to 2,010 BP;(iii) the third stratum (Layer 2 to U1/Fe5) consists ofgray sand (10YR4/1-6/1) layers and earth ovens
containing burned coral pebbles and charcoal
flecks. The components of these layers bear a resemblance to those of soil in the adjacent pits.
The layers also tend to descend to one of thesepits. These characteristics support the possibility
that the heap consists mainly of spoils dug up
from the pit. From the ovens as well as the spoil
layers, dolphin vertebrae and turtle remains wereretrieved along with bones of pelagic, benthic andreef fishes (Fig.8). We also obtained five radiocarbon ages associated with these ovens fromcharred flecks of Pacific rosewood and Chineselantern. They intriguingly fall within a narrowinterval around 1,800 BP.
Recent archaeological studies of the MarshallIslands in Eastern Micronesia have revealed that theprehistoric human settlements on several atolls dateback to the early period of the first millennium AD(Beardsley, 1993; Dye, 1987; Streck, 1990; Weisler,

31

1999a, 1999b, 2001)[1]. The earliest age from site
MJ-Lr2-8, 2,010 ± 50 BP (PlD-2790, AMS), falls
within this range. The preceding evidence from Laura
reported by the Bishop Museum (Riley, 1987) andWeisler (2000) also show a range of 1,800-2,000 BP.
It is, thus, almost certain that a group of Oceanicislanders arrived at Majuro Atoll around the first century AD, while other ages reported from Micronesia
and Polynesia suggest a later range of 1,000-500 BP
for initial settlements on atolls.
This time difference between the Marshalls andother atolls must be elucidated in detail from theviewpoints of geomorphology relating to atoll formation and cultural history with regard to human colonization, but two aspects should be here noted that:(a) surprisingly the age of 2,000 BP is almost
equivalent to the estimated end of the mid-Holocene
highstand of the sea level within the central Pacific.
The first settlers in the Marshall Islands would havelanded on islets newly occurring above the late
Holocene sea level. What is interesting is that theywould have been one of the first groups to have confronted the strange environment of remote atolls.
Recent geomorphological studies on atolls would be
relevant to an examination of this topic;(b) although the majority of atolls were previously
thought to have been temporally occupied at first andsettled later than high islands that would have beenFig. 8 Remains of sea mammals and fishbones from site MJ-Lr2-8.
1. Peponocephala electra / left premaxilla and maxilla (left: ventral, right: dorsal);
2-6. Delphinidae gen. Indet / lumber or caudal vertebrae; 7. Chelonidae gen. Indet / plastron;
8. Chelonidae gen. Indet / carapace; coastal scute (upper: dorsal, lower: ventral);
9. Chelonidae gen. Indet / left parietal (left: ventral, right: dorsal); 10. Scaridae gen. indet / left
dentary; 11. Cetoscarus bicolor / right premaxilla; 12. Cetoscarus bicolor / right dentary;
13. Labridae gen. indet / low pharyngeal; 14. Epinephelus sp. / right premaxilla;
15. Serranidae gen. indet / right maxilla; 16. Scombridae gen. indet / right quadrate;
17. Scombridae gen. indet / right premaxilla; 18-20. Scombridae gen. indet / caudal vertebrae;
21-22.Katsuwonus pelamis / caudal vertebrae; 23. Carangidae gen. indet / caudal vertebra.

32

T. YAMAGUCHI et al.

preferred as human habitation (Goodenough, 1957:
152; see also Alkire, 1978:20), Oceanic islanders
appear to have colonized the Marshall Islands during
as early a phase as the high islands such as Kosrae,
Pohnpei and Chuuk in Central Micronesia. This suggests that the first settlers on the Marshall atolls would
have transported knowledge or lore, including agronomic ones for cultivating aroids in wet edaphic soil,
which were helpful to their subsistence in the atoll
environment.
Both aspects are closely related to each other but
they will be discussed separately for convenience inthe following section.

3. Early Settlement on Laura Relating to Its
Geomorphological Formation
In the mid-Holocene period the paleoreef had upgrown to the highstand sea level over the bedrock of
Pleistocene limestone. It probably started to emerge
sometime after ca. 2,000 years ago (Tracey & Ladd,
1974; Buddemeier et al., 1975), and was fully exposed
when the subsequent decline of the sea level first carried its high-tide level below the mid-Holocene
low-tide level. This ‘cross-over’ date is estimatedaround 1,100 AD for the Marshall Islands (Dickinson,
2003). The archaeological evidence, however, indicates that wave build-up sediment may have rapidly
formed subaerial cores of some islets even though the
Holocene paleoreef flat still lay within the tidal range
and so it was overtopped by sea water at high tide.
We collected sand samples from the natural stratum at site MJ-Lr2-3 that was equivalent to the lowest
one (Layer 7) at site MJ-Lr2-8. It contained many
tests of large benthic foraminifera, mostly Calcarina
spp. Its availability had recently been illustrated forradiometric dating in a geomorphological study
on coral sand sedimentation (Yamano et al., 2001;
Yamano et al., 2002). Our samples of Calcarina preserving fresh spicules, which suggest that they weretransported and accumulated immediately after theirproduction in the vicinity of the reef edge, yielded twoages of 2,380±40 BP (Table 1): one associated withthe upper part of the natural stratum just below theearliest A horizon (Beta-191711) and the second withthe lower part just above the water table (Beta191714). While the ages have not been corrected forthe marine reservoir effect yet, they appear to support
the possibility that the core of Laura quickly occurredjust before the arrival of Oceanic islanders in MarshallIsland waters.
The physical variety of the islets should be, however, considered with reference to the timings of theiremergence and their geomorphological stability.
While it has been pointed out that coral islets quickly
emerged after a relative fall in the late Holocene sea
level (Schofield, 1977; Scoffin, 1993; Yamano et al.,
2000; Woodroffe & Morrison, 2001), it seems unrealistic to suppose that every islet was synchronously
formed, as the production of foraminifera and thesedimentary process are probably constrained by local
conditions (e.g., Marshall & Jacobson, 1985:16).
This is also suggested by the present variation of
islets in shape and size that is observable even in one
atoll. An islet with a shorter perimeter becomes morecircular and broader than one having an equal sizewith a longer perimeter. In a graph showing the distribution of sizes and widths of Majuro islets (Fig.9),
Laura is located at the uppermost right hand corner.
This means it is the largest and broadest islet in thisatoll. The present Laura accounts for 18% of the total
land area, while more than 80% of the islets are lessthan 0.2 km2 in area. Laura is the very islet associatedwith the earliest human settlement back to ca. 2,000
BP, while a smaller islet, Calalin, shows a muchyounger age of 360 BP (Riley, 1987:242).
The core of Laura was probably one of the few
atoll islets first occurring in Oceania during the
Holocene period, and it must have been one of firstatoll islets for Oceanic islanders to discover. According to our archaeological evidence, coconut and/or
pandanus trees appear to have already been grown in
its landscape at ca. 2,000 BP.

Fig. 9 Diversity of present Majuro islets in size and shape.

Excavation of Pit-Agriculture Landscape on Majuro Atoll, Marshall Islands, and Its Implications

atoll societies. For instance, the leaves stripped byhand from Chinese lantern are tramped in planting
beds of agricultural pits in Pukapuka Atoll of theNorthern Cook Islands (Beaglehole & Beaglehole,1938:89).
Our archaeological evidence indicates that the pit
agriculture landscape, consisting mainly of remarkable undulation and rich vegetation, was artificiallyconstructed around 1,800 BP and probably has been
maintained until the present without any destruction
by subsequent natural catastrophes or human activities.
What agencies would be associated with the inventionof this long-lasting landscape of pit agriculture on anatoll islet? We would have to consider the hydrogeologic and culture-historical factors at least.

4. Prehistoric Invention of Pit Agriculture
LandscapeAs already described, the third stratum in the
trench of MJ-Lr2-8 is interposed with earth ovens that
tend to descend in the same way as the spoil layers,
except for the lowest oven (U1/Fe5), which is the largest one more than 2 meters in diameter. It can be, thus,
speculated that the lowest oven was made before the
excavation of the adjoining agricultural pit began, andthe rest of ovens were used in the process which created the spoils piled up around the pit.
Of interest is, however, that the five radiocarbon
ages associated with these ovens including the lowest
and uppermost ones fall within a narrow interval ofaround 1,800 BP (Table 1). These ages imply that the
spoil bank was formed not gradually but over a shortperiod. The most reliable age is 1,720±45 BP (PLD2788) obtained from a charred phalange of pandanus
fruit, short-lived organic matter. It is thus very
plausible that the people on Laura not only widely
explored the marine resources (Najima & Yamaguchi,
2004) but also constructed the undulation of agricultural pit and spoil bank as early as some centuries after the earliest evidence of human colonization.
The charcoal samples also tell us about the pastvegetation although partially. The wood charcoalsfrom the third stratum were identified as those ofPacific rosewood (Cordia spp.) and Chinese lantern(Hernandia spp.) as well as pandanus and coconut
trees (Fig.10). These vegetable matters, in particular
those from Chinese lantern, have been described as
green fertilizers in some ethnographies of Oceanic

4.1 Hydrogeologic characteristics of Laura
Because the freshwater sits atop saline water permeating the porous underground of the islets, its quality and volume is affected by tidal and seasonal fluctuations in the water table that cause diffusion
between fresh and saline water. Its magnitude is inversely proportional to the width and size of the islets(Tracey et al., 1961).
The permeability of underground sediments ismore crucial to the fluctuation of water lenses. According to a hydrogeologic investigation, the nearsurface lithological framework beneath Laura comesin two primary hydrologic units (Anthony et al., 1989).
The lower represents a lagoonward-dipping unit thatwas sub-aerially exposed and leached during a Pleistocene glacial lowstand sea level. The upper unit is ‘anuncemented grainstone composed of a heterogeneous

1

2

3

11

12

13

4

5

6

14

15

16

17

18

19

7

8

9

10

33

Fig. 10 Identified charred woods from site MJ-Lr2-8.
1: Pandanus nut (cross grain); 2: Pandanus nut? (cut end); 3: enlarged no.2 (cut end);
4: Monocotyledon (cut end); 5: Monocotyledon (cut end); 6: Cocos nut? (cut end); 7: Cocos trunk?
(cut end); 8: enlarged no.7 (cut end); 9: Cocos trunk? (cut end); 10: enlarged no.9 (cut end);
11: Cordia (cut end); 12: Cordia (cross grain); 13: Cordia (straight grain); 14: Cordia (cut end);
15: Cordia (cross grain); 16: Cordia (straight grain); 17: Hernandia (cut end); 18: Hernandia (crossgrain); 19: Hernandia (straight grain).

34

T. YAMAGUCHI et al.

mixture of moderately well-sorted, foraminifera sandand fragments of coralline algae’ (ibid.:1068), while
its lower part contains a relatively higher abundanceof silt. This unconsolidated unit is markedly lesspermeable than the leached Pleistocene limestone andthe coral sequence of the Holocene reef that are moreporous or have cavities (Marshall & Jacobson, 1985;
Anthony et al., 1989).
Drillholes on Laura have revealed that the upper
unit of fine sand was ca. 25 m thick on the lagoonward edge and 16 m even inland. The sand’s lower
permeability and its thickness and width would prevent saline water from moving upward or inward into
the freshwater lens. While the sedimentary process
remain a matter of geomorphological speculation, it isprobably the accumulation of this foraminifera sand,along with rich precipitation averaging ca. 3,500 mm
in annual rainfall, which provides Laura the comparatively larger freshwater lens that has sustained its
vegetation and in particular the growth of Cyrtospermain the agricultural pits.
4.2 Transported knowledge of manipulatinghydromorphic terrain
The fortuitous hydrogeologic conditions are not,however, sufficient for pit agriculture landscape tohave been invented on Laura. The people would haveneeded knowledge on how to manipulate hydromorphic terrain in such a subtle way.
As with most languages in the Caroline andKiribati islands, all of those spoken throughout the
Marshall Islands belong to Nuclear Micronesian, oneof the Proto-Oceanic subgroups that are closely correlated with the eastward expansion of the Lapita cultural complex occurring around 3,500 BP in the vicinity of the Bismarck Archipelago. Archaeological excavations on three high islands in central Micronesia –Chuuk, Pohnpei and Kosrae – have revealed sandtempered plain-ware potsherds relating to the periodaround 2,000 BP. Their attributes in form and technology have been pointed out to bear a resemblance tothe late Lapita Plain Ware pottery tradition that
extended from the Bismarcks westwards as far as theReef-Santa Cruz Islands eastwards after 2,500 BP(e.g., Athens, 1990:29).
Both linguistic and archaeological evidences,
therefore, strongly indicate that the Marshall Islands
would have been colonized not from the west but thesouth, probably somewhere from the southeast
Solomon-Vanuatu region (Intoh, 1997:22; Kirch,
2000:175). A recent archaeological excavation on
Nikunau, a reef island in the Kiribati, has also revealed two early earth ovens dating approximately to
2,000 BP (Di Piazza, 1999). This evidence might suggest direct or indirect colonization of the Marshalls
from the south (see Fig.2). At any rate, Oceanicislanders moved northward from Melanesia and theyconsequently discovered around 2,000 BP the justemerged islets of remote atolls in Eastern Micronesia

as well as high islands in Central Micronesia. There islittle doubt that Laura was one of these islets.
Although it would be worthwhile to study whether
the Lapita people had practiced irrigation in Melanesia,
they probably cultivated both species of taro –Colocasia and Cyrtosperma – at least ‘in naturally
swampy swales behind the beach terraces where they
made their homes’ (Kirch, 1997:211; see also Kirch &Lepofsky, 1993)[2]. It would thus be plausible that oneof their groups transported to Laura the idea of cultivating swamp taro on hydromorphic terrain, fromwhich the later landscape modification would havebeen derived for their deliberate exploitation of richfreshwater resources.

5. Conclusions – Prehistoric Interaction
between Natural and Human Agencies –Our excavation on Laura, Majuro Atoll, in the
Marshall Islands, has revealed that its earliest colonization dates back to 2,000 BP and the agricultural pit
was constructed some centuries later. The earliest
colonists on Laura would have been one of firstgroups who could discovered atoll islets in Oceania,
as their subaerial landform would have emerged after
the relative fall of the late Holocene sea level, the timing of which is surprisingly estimated around 2,000
BP. Beneath Laura, however, had accumulated lowpermeable thick sediments of foraminiferal sand,extending down more than 16 m. These lagoonalfacies have advanced the occurrence and the enlargement of the freshwater lens, which would have been a
crucial condition for human subsistence.
The people on Laura may have cultivated wet taro,
probably Cyrtosperma, in low-lying natural swamps
on the basis of their own knowledge transported fromthe late Lapita cultural tradition. At least some centuries later, they deliberately constructed agriculturalpits to explore the rich freshwater resource and probably planted on the spoil banks tall trees of Pacificrosewood (Cordia spp.) and Chinese lantern(Hernandia spp.) as well as pandanus and coconut
trees, the organic matters of which would have been
also used as green fertilizers. The comprehensive
interpretation which is obvious from the synthesis ofvarious evidences is that the pit agriculture landscape,which we can see on Laura at present, is the historical
product of interaction or entanglement between
agencies both natural and human.
What is interesting is also that this landscape has
existed for a long time, more than 1,800 years. This
fact appears to bear out the relative stability of Lauraagainst natural catastrophes. It appears that atoll islets
are considerably weaker than high islands with regard
to rising sea level and climatic fluctuation, but there isalso variety to their vulnerability. A report that some
4,000 residents living in the city relocated themselves
to Laura when storm surges from Hurricane Alice
inundated the eastern part of Majuro in 1979

Excavation of Pit-Agriculture Landscape on Majuro Atoll, Marshall Islands, and Its Implications(Spennemann, 1998) also seems to suggest this. The
present pit agriculture landscape, comprising remarkable undulation and rich vegetation, can therefore beviewed as a historical indication of islets with goodconditions in aspects of both land formation andhuman subsistence.
Notes[1] The earliest radiocarbon age from the Bikini Atollis 3,450±60 BP (Streck, 1990). Judging from thetiming of the relative sea-level fall in the
mid-Holocene and the formative process of subaerial landforms on which the Oceanic islanders settled, however, the age is highly dubious and seems
to be from long-lived organic matter or old material
from driftlogs (e.g. Kirch & Weisler, 1994:292).
[2] The topic on the origin and development of Oceanic
irrigation systems seems to be related to a semantic
aspect of ‘irrigation.’ If this term embraces all
forms of ‘wetland’ agriculture from the use of naturally swampy areas to true systems of irrigationsuch as a pondfield (Spriggs, 1990:175), our evidence from Laura supports the view that the Lapita
people would have had knowledge of ‘irrigation.’

Acknowledgements
Our research projects were financially supported by
the Global Environmental Research Fund, Ministry ofEnvironment, Japan (2003-2005), and were assisted bymany people and the Government of Marshall Islands.
We wish to express our special gratitude to them, in particular Mr. Mudge Samuel (Mayor of Majuro Atoll) andstaff in Historic Preservation Office who provided us
with all possible assistance.

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