The not-for-profit says a pile of hedge trimmings were recently left on an earth bank near the car park, which is says could “spread diseases or invasive species.
“Fly tipping is never acceptable”
The reserve is part of the Grand Mare area – an important habitat for birds – and La Société says it is “probably the best area in the island” for dragon flies.
It noted that fly tipping has occurred repeatedly in the past on other reserves, especially Le Grand Pre in the Vale.
La Société has held several parcels of land as nature reserves since the 1970s.