MORE resources are needed to protect the Sand Dunes after butterfly declines exposed the worsening condition of the protected site, a new report has warned.
Three butterfly species – the Essex Skipper, Speckled Wood and Small Copper – experienced statistically significant declines along a survey route through the St Ouen site between 2004 and 2023.
The Jersey Butterfly Monitoring Scheme’s 20-year report said that although rangers and volunteers carried out scrub removal, dune stabilisation and other management work, time and resources were “scarce”.
It concluded that “more resources are required to help protect this special site and conserve its precious habitats”.
Small Copper numbers fell by 66% at Les Blanches Banques despite increasing by 122% across Jersey during the same period.
The Essex Skipper declined by 69% at the dunes, while Speckled Wood numbers dropped by 51%.
Several other species which are increasing across Jersey also fell at Les Blanches Banques, although those local declines were not statistically significant.
The Meadow Brown increased by 49% Island-wide but declined by 70% at the site, while the Red Admiral rose by 99% across Jersey but fell by 87% there. The Brown Argus increased by 228% Island-wide but declined by 88% at the dunes.
The report said it was “striking” that many more species were showing downward trends at Les Blanches Banques than across Jersey generally.
“It is as yet unclear as to why butterfly populations are in decline at this site, but it is most likely attributed to habitat change,” it stated.
The Site of Special Interest contains species-rich dune grassland and more than 400 recorded plant species. Its grey-dune habitat is recognised as being of conservation importance under the EU Habitats Directive.
However, assessments conducted in 2020 and 2025 found that the site’s key grey- and yellow-dune habitats had failed to achieve favourable condition, while scrub had expanded.
Separate mapping found that scrub on the lower dune plain increased by 8,803 square metres between 2014 and 2025 – an 83% rise within the area studied.
The report said scrub encroachment had progressed to the point that trees were growing where dune habitat once existed.
The spread of scrub and Burnet Rose is thought to be crowding out plants that are important to the protected site, potentially harming insect numbers and diversity.
