Invasive species controlled at Potteric Carr Nature Reserve
Thursday 19th December 2013
Crassula control at Potteric Carr Nature Reserve - Credit Jim Horsfall
Control work is currently being undertaken at Potteric Carr Nature Reserve to reduce invasive species.
ECUS, an environmental consultancy based in Sheffield, are working with Yorkshire Wildlife Trust to target invasive species, Crassula helmsii (also known as New Zealand pigmyweed or swamp stonecrop) growing on its nature reserve, Potteric Carr, near Doncaster.
A section of the nature reserve known as Willow Marsh, has been drained of water and a large digger is being used to scrape off as much of the plant species as possible from the currently empty lake. The plant matter removed is then being piled under other material to compost. In a few months when Crassula helmsii has died, the material will be removed.
This process will not eradicate the problem completely but will reduce it to a level that is much more manageable. It iwll also be less likely to spread.
Whilst it looks like a destructive process, as the water is drained out and the vegetation scraped out, it will have a positive effect and in a few months the water levels will rise again and the native vegetation start to return.
Crassula helmsii causes a problem as it is an aggresive grower and can completely cover the margins of ponds and lakes, excluding all other small plants that would otherwise grow. In very bad infestastions (such as at Willow Marsh) it can become aquatic spreading from the margins towards the centre of the lake. It creates so much vegetation that light and oxygen don't reach the bottom of the lake, which can reduce insect and fish numbers, and consequently, the birds and other things that feed on these.
Crassula helmsii is one of several invasive non-native species that will be illegal to buy from 2014 due to the immense negative impact that they can have on natural habitats and species.