Acacia nilotica was introduced to Baluran National Park (BNP) in 1969 to serve as firebreaks. It quickly invaded the Bekol Savanna in BNP, where it inhibited the growth of native grasses that are important food for wildlife, such as the endangered banteng (Bos javanicus). To determine the effect of A. nilotica invasion on plant species assemblages and diversity and to evaluate how well the management technique is preventing further invasion and restoring the native ecosystem, we laid out 25 plots (10 m × 10 m) in a belt transect in each of three vegetation types: uninvaded area (UIA), invaded area (IA), and managed area (MA) where the slash and burn method has been attempting. In each vegetation type, we counted the number of individuals of each plant species and calculated the species richness and diversity indices. The results showed that the savanna changed dramatically after the introduction of A. nilotica. Seven of the nine species detected in UIA were absent from IA, and the relative dominance of surviving plants also decreased. Consequently, the diversity of the savanna was degraded by A. nilotica invasion, causing a reduction of food resources for herbivores. In MA, however, five of the seven species absent from IA had recovered after the slash-and-burn removal of A. nilotica. Several forest species had newly invaded MA owing to both the decreased allelopathic influence and the perch effects of remnant A. nilotica. Thus, the slash-and-burn method could contribute to the recovery of native species, although additional efforts are required to remove remnant A. nilotica.

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Because of natural disasters caused by a heavy rain and change of precipitation pattern, rice production in West Africa is often unstable, whereas rice is an important food crop. Reports of flooding damage to rice plants have been increasing with the expansion of rainfed lowland rice cultivation there since 1988. This report reviews recent environmental changes that have occurred in a flood-prone region of West Africa, and the eco-physiological survival strategies used by rice plants under flooding stress. We identify the flooding status in West Africa, with flood-prone areas that are classifiable into three types: floating, deepwater, and flash flood areas. Most rice cultivars show shoot elongation in response to submergence. Shoot elongation during long-term submergence is an‘ escape strategy’, which enables rice to resume functioning when again in aerobic conditions. However, some rice genotypes can survive in flash flood areas due to tolerance to short-term submergence. The ecological and physiological traits of flash flood-tolerant rice include less chlorosis and high carbohydrate reserve storage, although shoot and leaf elongation are slow during submergence. Especially for flood-prone areas, we report the potential adaptability of Oryza glaberrima Steud., one cultivated species of rice originating from Africa, which has unique traits of increased biomass production through high photosynthesis by newly developed leaves under prolonged submergence. We conclude that stable agricultural systems with useful tolerance to flooding stress should be improved grain yield to mitigate submergence damage to rice crops in West Africa.

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