[H-GG01] 自然資源・環境に関する地球科学と社会科学の対話

[HGG01-P05] Mangrove ecosystems in the coastal region of western India utilized for traditional pastoralism: effects of climate change and social conditions on long-term biomass change

*大手 信人¹、山本 凱¹、チャッタジー ラニット¹、ジョシ パンカジ²、スリバスタバ シルピ³、メータ ライラ³ (1.京都大学大学院情報学研究科社会情報学専攻、2.サジーバン、3.英国開発学研究所)

キーワード：マングローブ、カッチ地方、長期動態、伝統的牧畜

Mangroves cover a large area of the coastal region of Kutch in western India. The Maldharis, the inhabitants of this region, have been using mangrove forests for traditional livelihoods such as the rearing of Kharai camel, which feeds mainly on mangrove leaves. The objective of our interdisciplinary project is to explore the direction of changes for the sustainability of this community. Since the linkage between the ecosystem services of the mangrove forests and the traditional pastoralism of this community is one important aspect to consider, a clear description of the historical evolution of this ecosystem is an important step for basic information. We are using satellite remote sensing data to develop a quantitative description of mangrove biomass since the1980s. Using Landsat multispectral imageries, we calculated spatial averages of NDVI for several target forest components. The overall NDVI of mangrove forests in the region has increased from 1988 to the present, suggesting an increase in biomass. However, it has been decreasing from the late 1990s to the early 2000s. The most likely reason is that the low precipitation (drought) in the late 1990s to early 2000s increased the salinity of soil and groundwater, which in turn increased water stress. Contrastingly, the lack of significant changes in NDVI due to a single year of drought suggests that mangrove forests are resilient to drought. On the other hand, it is inferred that several factors were involved in the increase of NDVI since the early 2000s. Two of these factors are the higher precipitation during this period and the fact that the Forest Department has been restricting pastoralists' access to mangrove forests since 2005. These results suggest that climatic conditions and pastoralism intensity influence the long-term variation of NDVI values in each forest segment. This also suggests that local pastoralists harvested leaves and branches from the mangrove forests as resources but did not destructively take forest trees. This confirmes that the Maldharis base their livelihood on maintaining the mangrove forests.