Create regular tunnels under the railway to connect habitats and provide safe passage for wildlife. This should be a mixture of small tunnels for small mammals, invertebrates and amphibians, large tunnels for deer and badgers, and culverts for aquatic/semi-aquatic life.
You may be interested in these active petitions
Overground areas of HS2 pose a variety of threats to wildlife by blocking movement or causing direct mortality. Wildlife tunnels can mitigate these effects by connecting fragmented urban and rural habitat and reducing collisions - it has been extremely successful with other infrastructure projects across the world. Connectivity is vital for maintaining genetic diversity and allowing animals assess different territories, resources and mates; all vital for preventing further species decline.