Number of native and non-native ruderal species over time
The total number of ruderal species did not increase significantly over time from 1903 until 2021 (Fig. 2, supplementary Table 1), with highest richness in 1913 (69 ± 10 species) and the lowest in 1983 (19 ± 8 species). The number of non-native ruderal species decreased significantly over that 120-year period from 69 in 1913 to 36 in 2021 (Fig. 2, supplementary Table 2). For both the total and non-native ruderals, 1983 showed the lowest species richness. Finally, ruderal communities were more dissimilar between the different surveys than subregions (supplementary Fig. 4), except for 1983 which had higher variation between subregions.