Swamp stonecrop (Crassula helmsii)

The swamp stonecrop is considered an invasive species in the Netherlands (as in a number of other countries). The first observation was in the Netherlands was in 1995. Control of watercrassula is deemed necessary: ​​every 10% increase in watercrassula results in a 5% decrease in native vegetation and has also been shown to have a negative impact on native zooplankton and fauna.
(source: https://www.naturetoday.com/intl/nl/nature-reports/message/?msg=23106 - Dutch)