Temporal changes in taxon richness of macrophytes were analyzed from ten lakes of Japan, in which flora records are available covering the last 60 years. In addition, the recovery potential of locally extinct taxa was analyzed using data of soil seed banks in lake sediments, which are recognized as a promising source for restoration.

Among the ten lakes analyzed, a marked decline in taxon richness was observed, and 50% or more of the past flora had disappeared between the 1970s and 1990s in six lakes. In Lake Kasumigaura, for example, 31 macrophyte taxa were recorded in the 1970s but in the 1990s, only 13 were recorded.

Recent soil seed bank data were available for Lakes Kasumigaura and Inba-numa. Analyses of the relationship between the presence of viable seeds in the seed banks since 2000 and time of disappearance from aboveground vegetation for each species revealed that more than 50% of taxa which had disappeared in the 1990s were remained in the seed banks. For taxa that had disappeared before 1970s, however, no species were recorded in the seed bank records, suggesting that recovering taxa that had disappeared more than 30 years ago might be difficult. Considering that taxon richness had rapidly decreased since the 1970s, efforts for restoration of aquatic vegetation from soil seed banks are now very urgent tasks.