Analyses of a sediment core from Little Pond, located in the town of Bolton, Massachusetts, provide new insights into the history of environmental and ecological changes in southern New England during the late Holocene. Declines in organic content and peaks in the abundance of Isoetes spores indicate reduced water depth at 2900–2600, 2200–1800, and 1200–800 calibrated years before present (cal yr BP), generally consistent with the timing of dry conditions in records from elsewhere in the northeastern United States. The Little Pond pollen record features little change over the last 3000 yr, indicating that the surrounding vegetation was relatively insensitive to these periods of drought. The 1200–800 cal yr BP dry interval, however, coincides with increased abundance of Castanea pollen, suggesting that the expansion of Castanea in southern New England may have been influenced by late-Holocene climatic variability.

There are four known species of Isoetes (Family Isoetaceae) from China: I. hypsophila, I. sinensis and I. yunguiensis on the mainland, and I. taiwanensis on Taiwan. In a 4-year study we documented the distribution and habitat characteristics of all four species and evaluated their conservation status using IUCN criteria. All four species are facing a high risk of extinction and should be categorized as Critically Endangered on the IUCN Red List. Habitat degradation and loss, water pollution and eutrophication, competitive exclusion, and human disturbance are the main factors causing the decline and extirpation of Isoetes. Only I. taiwanensis is protected in situ in Yangmingshan National Park on Taiwan. None of the species or habitats of Isoetes on mainland China are presently protected, although all species have been designated by the government as State Key Protected Wild Plants. Our results suggest that conservation strategies should be implemented urgently, particularly on the mainland.