Crassula helmsii

Swamp stonecrop

Crassula helmsii is an evergreen perennial aquatic plant that is able to grow both submerged (under water) and emersed (above water). Submerged stems are long, thin and branched, whereas emersed stems are shorter, fleshy and less branched. The leaves are arranged opposite, fleshy and linear in shape, about 4-20 mm long and 0.8-2 mm wide. They are smooth and glossy, with a light green to yellow-green colour. The plant produces small, white, four-petalled flowers on short stems, mainly from July to September. Crassula helmsii prefers stagnant or slow-flowing freshwater environments and can grow in a wide range of light conditions, from full sun to deep shade. Its ability to grow quickly and reproduce vegetatively has contributed to its spread and invasive potential.

Types of damage

Ecological damage

Crassula helmsii can quickly dominate in new environments, displacing native flora. It forms dense mats that can block light and reduce the oxygen content of the water, which is detrimental to fish and other aquatic life and can reduce the reproductive success of amphibians (for example crested newts).

Economical damage

Crassula helmsii can clog watercourses, irrigation canals and drainage ditches in dense monocultures. In addition, the plant can interfere with recreational use of water bodies such as fishing and swimming.

Region of origin

Australia and New Zealand

Introduction vectors

Trade with ornamental plants

Crassula helmsii was originally introduced to many countries because it was used as a decorative aquatic plant in garden ponds and aquariums.

Unintentional introduction

Crassula helmsii can reproduce by small fragments that can easily stick to shoes, clothing or equipment and thus be introduced into new areas. This can happen especially during activities such as fishing or water construction operations.

Current distribution

Based on the FlorKart Database of the Federal Agency for Nature Conservation, as of 2013

Miscellaneous

Family

The Crassulaceae family comprise about 34 genera with about 1,400 species. They are distributed worldwide, with the greatest diversity in the arid regions of the northern hemisphere. The plants of this family are known for their adaptability to dry environments through their succulent, i.e. water-containing, leaves and stems. Many species use CAM photosynthesis, which allows for efficient water management. This family includes many popular houseplants and garden plants, such as the genera Sedum (stonecrop), Sempervivum (houseleek) and Echeveria.

Climate change

Crassula helmsii has not yet filled its potentially suitable habitat under current climate conditions. It benefits from climate change because in the future its potentially suitable habitat will increase. The environmental factors that most influence its spread are soil type, road infrastructure, summer precipitation, waterways and rail infrastructure.

Dispersion forecast

Indicates the proportion of land suitable for habitat under current and future climate conditions (2060-2080) under three emission scenarios (RCP26, RCP45 & RCP85).

Habitat suitability maps

Instructions for use: Click here

Habitat suitability under current climate conditions

These habitat suitability maps show for Crassula helmsii where suitable habitat conditions exist.

The map on the left shows this for current climate conditions. Below this are maps for the time classes 2040-2060 and 2061-2080, in which three different emission scenarios can be selected.

The slider at the top left allows you to adjust the opacity of the map to make orientation easier.

By clicking on the respective quadrant, information on the environmental conditions present in it can be called up.

The methodology is explained here .

Habitat suitability 2040 - 2060

2040-2060: In the RCP2.6 scenario, GHG emissions are expected to peak by 2040 through comprehensive mitigation measures and to decline rapidly thereafter. By 2060, global warming would stabilise at about 1.5°C above pre-industrial levels. Subtle changes in precipitation patterns could vary regionally, with some areas facing increased drought and others increased precipitation.

2040-2060: Under RCP4.5, GHG emissions would continue to increase until 2040, but stabilise at a high level thereafter. By 2060, there could be a global temperature increase of about 2°C above pre-industrial levels. This scenario would likely cause moderate changes in precipitation patterns, with potential regional differences.

2040-2060: Under RCP8.5, which assumes intensive use of fossil fuels, greenhouse gas emissions would rise sharply by 2060. The global temperature increase could be around 2.5-3°C. In this scenario, significant changes in precipitation patterns could occur, with an increased likelihood of extreme weather events.

Habitat suitability 2061 - 2080

2060-2080: By 2080, global warming could be limited to below 2°C in the RCP2.6 scenario, provided emission reductions are consistently pursued. Impacts on precipitation patterns would likely stabilise, although regional variance would remain significant.

2060-2080: In the RCP4.5 scenario, global temperatures would continue to increase and could be around 2.5°C above pre-industrial levels by 2080. Changes in precipitation patterns would likely increase and regional differences could become more pronounced.

2060-2080: Under RCP8.5, global temperatures could rise by more than 4°C above pre-industrial levels by 2080. Precipitation patterns would be expected to change significantly, with further increases in the frequency and intensity of extreme weather events. This would have far-reaching impacts on ecological and socio-economic systems.