| Summary: | To evaluate the effect of vegetation change on greenhouse gas (GHG) budget from a wetland ecosystem, the CO<sub>2</sub>, CH<sub>4</sub> and N<sub>2</sub>O budgets from whole area (21.5 ha) of the Bibai Wetland, where dwarf bamboo (<i>Sasa</i>) or <i>Ilex</i> has invaded into original <i>Sphagnum</i> dominated vegetation, located in Hokkaido, Japan were estimated. The original <i>Sphagnum</i>-dominated vegetation was changed from a sink to a source of CO<sub>2</sub> by invasion of short-<i>Sasa</i> (50 cm > height), while the invasion of tall-<i>Sasa</i> (50 cm < height < 150 cm) or <i>Ilex</i> increased CO<sub>2</sub> uptake. Annual CH<sub>4</sub> emission was decreased by the invasion of <i>Sasa</i> or <i>Ilex</i>. The annual N<sub>2</sub>O emission was slightly increased by invasion of <i>Ilex</i> only. These GHG budgets were correlated with the environmental factors related to the water table depth. The distribution of vegetation and environmental factors was estimated from satellite image bands, and the GHG budget of the entire wetland was estimated. The whole wetland area was considered to be a sink for GHG (−113 Mg CO<sub>2</sub>-eq y<sup>−1</sup>) and CO<sub>2</sub> uptake by tall-<i>Sasa</i> occupied 71% of the GHG budget. The vegetation change due to the lowering of the water table depth currently increases the rate of carbon accumulation in the ecosystem by about 5 times.
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