On a cultivation site located on a small barrier island, I encountered and interviewed an older man who was making mounds for new tuber crops:
Q: “When did you start using this land as a crop garden?”
A: “Oh, a very long time ago. I can’t say exactly when.”
Q: “What was here when you started using the land for the most recent crops?”
A: “It was my parents’ garden.”
Q: “I mean, in your cultivation cycle I want to know how long you cultivate this land and how frequently you leave it for fallow and soil recovery.”
A: “I don’t know about the cycle or fallow.”
Using different islands in different ways
This was in 2001, during my first fieldwork. Before coming to Roviana Lagoon in the Western Province of Solomon Islands, I had learned in textbooks that people in tropical rainforests usually shifted crop cultivation based on a cycle (for a few years) and long-term (usually over a decade) fallow for soil recovery. When I interviewed people cultivating crop gardens on the large New Georgia Island (the “main island”) where the village settlement was also located, I found evidence to back the assumption that this fallow period was vital for soil nutrients. Later, however, I found that villagers had gardens on a small barrier island located more than 5 km offshore from the settlement, and they canoed there for cultivation. I then tried to confirm that the cycle on the barrier island was the same as that on the main island, but the villagers’ answers to my questions were confounding because they insisted, as in the conversation above, that the fallow period was very short or sometimes there was none at all.
Left: A garden on the barrier island surrounded by secondary forest. There are no felled trees. Right: A villager preparing a crop garden on the main island. Note there are a number of large fallow trees felled, unlike on the barrier island on left.
I confirmed that all villagers agreed they could cultivate land continuously on the barrier islands, unlike on the main island. They called the ecological settings of the former tutupeka and the latter toba. I then analyzed aerial photographs taken in 1947, 1969, and a high-resolution satellite image from 2002. Many parts of the cleared land overlapped throughout the three images, which supported the villagers’ claims. Soil nutrients, especially phosphorus, were also higher on the barrier island than on the main island. Crop productivity (energy produced per area) was only slightly lower on the barrier island, even though the extremely short fallow period was adopted. I calculated the carrying capacities of the main and barrier islands based on their cultivation cycles, energy produced per area per year, arable land area, and population size, and found that a small portion of the land on the barrier island was enough to sustainably satisfy the energy requirements of all of the villagers. Also notable was that although they used traditional production styles and management on the barrier island, on the main island they used risk-prone Western-style practices, such as maintaining introduced perennial cash crops. (See Furusawa and Ohtsuka (2009) for details.)
People’s contribution to biodiversity through subsistence
Through this experience, I learned about the existence of something important not found in textbooks. Academically speaking, I also found that landscapes and people’s land use were extremely diverse between the two islands. Another interesting example was vegetation called rizevu—derived from the English word “reserve”—on the main island. In the 1970s, when forest development was extended to this area, village leaders decided to make two areas into rizevu, where forest clearing was prohibited but traditional use of forest, such as collection of materials for everyday uses (e.g., fuel, building traditional houses), and of non-timber forest resources, was allowed. Our vegetation survey found that the rizevu had a mixed feature of a primary forest (similarity index was 49.5%) and secondary forest (45.9%) as some pioneer tree species were found only in these areas, displaying the original type of forest. This suggested that continuous small-scale impacts had created unique vegetation and thus biodiversity. Before development (e.g., logging, cash cropping) started, these types of vegetation might have been the major type of forest, because there was no power (thus no chainsaws) and no reason to clear the forest. Furusawa et al. (2014) published more comprehensive data and analyses on this.
A typical non-timber forest product (Parinari glaberrima) that was collected in the rizevu. Its fruit is shredded or pounded to make putty for repairing holes and cracks in canoes.
The Roviana people used different islands and vegetation for different purposes to support their lives, but their wise use of the forest contributed to the creation and conservation of biodiversity.
Dr. Takuro Furusawa is an associate professor in the Graduate School of Asian and African Area Studies at Kyoto University. His main area of study is human ecology, specifially how people survive and maintain their health by using and depending on ecosystems.
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