The purpose of this study is to identify the effects of urbanisation on the distribution of alien plants. The survey was taken twice a year (spring and autumn) between 2004 and 2013 in 145 districts of Fuchu, Tokyo. The data set was compared to a historical data set (1970-1981) for analysis. The effect of environmental factors was tested on the proportion of alien species.

In total, 1170 plant species were recorded of which 408 were alien species. Over the last three decades 226 species have disappeared and 504 species were introduced. The proportion of alien species has increased from 20% to 35% in Fuchu city as a whole. The average proportion of alien species across the districts was 38%. This proportion has a positive correlation with human population, human population density, road and building area ratio and city area ratio, and a negative correlation with the green coverage ratio and number of vegetation type. Among these environmental factors, the road and building area ratio was the best estimate factor (GLMM).

From the results, the proportion of alien plants has increased with city developments and these species are more successful in highly urbanised areas.