Name 四方 篝/SHIKATA-YASUOKA Kagari Nationality 日本/JAPAN Research theme アフリカ熱帯雨林における焼畑の潜在力を活用した農業と森林保全の両立 Agroecological study of banana-based shifting cultivation: toward sustainable agriculture and biodiversity conservation in African rainforest Key Words African rainforest, shifting cultivation, agroforestry, plantain-banana, cocoa, Cameroon Introduction アフリカ熱帯雨林では,農地の拡大や商業伐採による森林面積の縮小が深刻な問題となってお り,地域住民の生活と森林保全の両立をいかにして実現するのかが課題となっています。わたしは これまで,カメルーン東南部に居住する焼畑農耕民バンガンドゥを対象として 27 か月にわたるフ ィールドワークをおこない,かれらの農業実践や森林資源利用の実態を明らかにしてきました。 調査の結果,バンガンドゥの焼畑を基盤とする農業実践は,自給作物バナナの安定した供給,森 林の循環的・持続的利用,多様な生態景観の創出とその利用,自給作物栽培と商品作物であるカカ オ栽培との併存など,農業と森林保全の両立に寄与するさまざまな潜在力をもっていることが明ら かになりました。 農業と森林保全の両立へ向けた従来のアプローチでは,移動耕作に特徴づけられる焼畑は森林破 壊的な農法とされ,それに代わる農法として常畑として維持するカカオ・アグロフォレストリーが 注目されてきました。しかしながら,カメルーン東南部のカカオ栽培は森林を循環的に利用する焼 畑と融合したかたちで実践されていることがわかりました。すなわち,焼畑と同じように「森にも どる畑」においてカカオ栽培が実践されています。このことから,常畑としてのアグロフォレスト リーではなく,焼畑のポジティブな側面(=焼畑の潜在力)を引き出すことが,住民生活と森林保 全の両立に貢献するのではないかと考えています。 Conservation of tropical rainforests with their rich biological diversity and high potentials for carbon sequestration has become a major global issue. My study focused on banana-based shifting cultivation system of the Bangando farmers who live in the tropical rainforest of southeastern Cameroon and investigated its agroecological functions for sustainable agriculture and biodiversity conservation. People grow a variety of plantain-bananas as their staple food, and harvest them throughout the year by staggering the planting season and using varieties that have different growth periods. This banana-based cultivation system is maintained by the periodical use of the secondary forest dominated by the quick-growing tree Musanga cecropioides R. Br., in which weeding is practiced for only one year after clearing and then abandoned thereafter. Plantain-bananas keep growing and fruiting even in such bush-like “fallow fields”, and people can therefore continue harvesting them from several fields opened in the previous years. These “fallow fields” comprising complex mosaics of different stages of ecological succession also provide several kinds of resources in the form of non-timber forest products (NTFPs). In addition, people have integrated cocoa growing into the system through a prolonged fallow cycle of several decades and tolerance of forest regrowth. The expansion of cash crop production often causes deforestation and dramatic changes of cropping system, then threatens subsistence crop production. This banana-based shifting cultivation system, however, has remained largely unchanged by the introduction of cocoa growing, in which the same principle of shifting cultivation is adopted for the new crop. It can reduce the risk of uncertain fluctuation of cocoa prices and productivity by stable banana production and a variety of NTFPs derived from biodiversity in young and old fallows. Consequently, Bangando’s banana-based shifting cultivation system has several agroecological functions for securing co-benefit of local communities and biodiversity; such as sustainable crop production, sustainable forest use, creation and utilization of ecological landscape diversity and adaptation to new economic demands. プランテン・バナナを収穫するバンガンドゥの女性 Bangando woman cultivated plantain-bananas. プランテン・バナナとカカオが混植された畑の景観 Plantain-bananas and cocoa trees are mixcropped in a field.
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