Study on the changing characteristics of land use as commons in Roviana, western province, Solomon Islands using high resolution satellite data and aerial photographs
Takuro Furusawa,Krishna Pahari,Ryutaro Ohtsuka
Department of Human Ecology, School of International Health
University of Tokyo
7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
Tel: (81) -3- 5841-3486
Fax: (81)-3-5841- 3395
Email: takk @humeco.m.u-tokyo.ac.jp
Masahiro Umezaki
Section of International Health
Graduate School of Tokyo Medical and Dental University
1-5-45 Yushima, Bunkyo-ku, Tokyo 113 -8519, Japan
Tel: (81) -3- 5803-5188
Fax: (81)-3-3818- 7176
Abstract
Tropical rain forests in Asia- Pacific area are disappearing due to logging operation by
multinational companies and also due to traditional and modern uses by local people. Remote sensing
has been widely applied to monitor the changes in land cover over time, though few studies in rural
areas have used the high resolution satellite data such as IKONOS. This study aims to observe the
spatio-temporal change in land cover and land use patterns in a village of Solomon Islands, where
commercial logging was operated in 1993. The village territory consists of two parts: a larger island, in
which logging and other deforestation have been under progress, and a smaller reef island, in which only
exclusive horticulture has been done. The IKONOS data acquired in 2002, colored aerial photographs
in 1991, black-and- white aerial photographs in 1969 and 1947 were analyzed to estimate land cover and
land use of the areas and they were compared to elucidate the changing process.
Introduction
Tropical rain forests in Asia-Pacific region are rapidly changing owing to logging operation by
multinational companies as well as utilization of lands for traditional subsistence and/or cash-earning
activities by local people under the influences of a variety of factors such as economic development and
population i ncrease.
Shifting cultivation, which has been traditionally practiced in limited area with rotati on, is sustainable, if
the period of cultivation is short enough and the period of fallow is long enough for the soil to recover its
fertility (Whitmore, 1998).
In Western Province of Solomon Islands, the use of land under the communal control and utilization has
been changing since 1980s when economic development commenced.
Remote sensing using high resolution satellites such as IKONOS has potentials to assess the
environmental changes. Few studies, however, have been conducted in local areas of Asia- Pacific
tropics, and none in Solomon Islands.
This study aimed to investigate changes in land use in a portion of New Georgia Island (called
Dekurana) in Western Province of Solomon Islands by comparing IKONOS image in 2002 and aerial
photographs in 1991. In the target area, the commercial logging was operated and the inhabitants have
been engaged in their cash-earning activities as well as horticulture. Also, spatio- temporal change in
land use was investigated in a nearby reef island (called Dora), in which horticulture had been conducted
exclusively since a few centuries before; aerial photographs in 1969 and 1947 and IKONOS image in
2002 were used.
Study Areas and Field Survey
The field survey was conducted in January to October in 2001 and May to July in 2002 in Dekurana and
Dora Island; the boundary of Dekurana area was defined by the high court of Solomon Islands (High
Court of Solomon Islands, 19 94). Both areas were used by Olive village of Saikile tribe in Roviana
Lagoon (Figure 1). There were 347 inhabitants in 49 households in February 2001, and most of them
were engaged in horticulture of tuberous crops and fishing. The two areas had been u tilized by not only
Olive villagers but also other people of Saikile tribe, whose number was similar to Olive, although
gardens (future tree plantation) along the main logging roads and the areas just surrounding Olive
settlement in Dekurana were used intensively by the Olive villagers.
In the Olive village’s territory (Dekurana area), the reforestation or plantation of introduced tree species
such as Eucalyptus deglupta and Tectona grandis have been conducted since 1997 for the purpose of
future cash income of the community. It had been particularly intensified since 2001 when the
community gave permission for each household to clear and use one ha of land along the logging road.
These lands were used as gardens for 2 years after clearance and tree planting; the garden making was
beneficial for protection of soils from the strong sunshine and rainfall and for minimization of labor for
horticulture and maintenance of planted trees.
The remote-sensing analyses focused on two areas (Figure 1) where the villagers practice almost all
their subsistence activities, such as horticulture, gathering foods and materials, and private saw-milling.
These two areas differed characteristically. Dekurana had started to be cleared for horticulture or
construction of coconut plantations since the end of 1960s and used for the cultivation of cash crops
(e.g., cacao) and tree plantation recently.
Dora Island had been used exclusively for gardens since a few centuries ago, though limited areas had
been used for tree plantati ons and cash crop groves. The natural soil composition was far richer in
Dora Island than in New Georgia Island (Hansell et al., 1975). According to the authors ’ observation i n
2001, 67.1% of gardens of 14 households in Olive were made in Dekurana and 31.8% in Dora Island.
Figure 1. The location of Olive and two areas analyzed remote sensing.
