Allerthorpe Common Nature Reserve is a mosaic of habitat types - dry heath, wet heath, marshy grassland, mire, tall grass, bracken, ponds, broadleaved woodland and scrub.

The reserve supports a large number of invertebrates. Listed here are some of the rarer species.

There are healthy populations of Adders and Common lizards in the reserve. Nationally, both species have declined in numbers and distribution, due to habitat fragmentation and collecting for the pet trade.

The ponds within the reserve support a breeding colony of Palmate newts and Great crested newts have also been found on the reserve.

Allerthorpe supports typical heathland plant communities and characteristic wet heath plant species. The site was surveyed in 1997 to National Vegetation Classification (NVC) enabling the plant communities to be described in more depth.