Flora and fauna thumb|right|A kangaroo of Onkaparinga River National Park The vegetation of the park has been greatly perturbed by human activity, but remnant patches remain. The most intact area is the Hardy's Scrub section of the reserve. 160 years of livestock grazing, timber harvesting and cropping has cleared most of the reserve of native understorey species and in many areas invasive grasses are the main vegetation type. Remnant eucalypts are the most noticeable native species in the reserve. Eucalyptus microcarpa (grey box), Eucalyptus fasciculosa (pink gum), Eucalyptus porosa (mallee box), Eucalyptus camaldulensis (red gum), and Eucalyptus leucoxylon (blue gum) all occur in the reserve. The European olive (Olea europaea) is a noxious weed in South Australia and has invaded the park, although generally individuals are not as large as in older parks in the Mount Lofty Ranges like Belair National Park but will continue to be a problem unless managed. Over the last twenty years accessible areas of the gorge have been revegetated by contractors working for National Parks SA. The oldest area of revegetation in the park was conducted with tubestock, predominantly of eucalypts. Recent efforts have focused on the direct seeding method where seed of native species is ploughed into a scraped trench. Insect activity includes butterflies (Lepidoptera) and dragonflies (Anisoptera). Kangaroos are common among the open hillsides with abundant grasses.
Flora and fauna thumb|right|A kangaroo of Onkaparinga River National Park The vegetation of the park has been greatly perturbed by human activity, but remnant patches remain. The most intact area is the Hardy's Scrub section of the reserve. 160 years of livestock grazing, timber harvesting and cropping has cleared most of the reserve of native understorey species and in many areas invasive grasses are the main vegetation type. Remnant eucalypts are the most noticeable native species in the reserve. Eucalyptus microcarpa (grey box), Eucalyptus fasciculosa (pink gum), Eucalyptus porosa (mallee box), Eucalyptus camaldulensis (red gum), and Eucalyptus leucoxylon (blue gum) all occur in the reserve. The European olive (Olea europaea) is a noxious weed in South Australia and has invaded the park, although generally individuals are not as large as in older parks in the Mount Lofty Ranges like Belair National Park but will continue to be a problem unless managed. Over the last twenty years accessible areas of the gorge have been revegetated by contractors working for National Parks SA. The oldest area of revegetation in the park was conducted with tubestock, predominantly of eucalypts Recent efforts have focused on the direct seeding method where seed of native species is ploughed into a scraped trench. Insect activity includes butterflies (Lepidoptera) and dragonflies (Anisoptera). Kangaroos are common among the open hillsides with abundant grasses.