The stretch of river between Thorncroft Manor ( south of Leatherhead) and River Lane in Fetcham has been designated a Local Nature Reserve. Although much of the surrounding land has been taken by residential and commercial development, this section of the Mole supports 20 different mammal species, 20 butterfly species and 15 species of dragonfly. The geology of the local area is complex, since the river leaves the chalk of the Mole Gap at this point and flows over gravel and clay, creating a patchwork of different habitats including scrub, woodland, hedges, banks, and meadows as well as the water itself. The river also provides a corridor for wildlife through the centre of Leatherhead.