The addition of ponds in gardens provides excellent habitat for wildlife, with opportunities for amphibians as well as reptiles, birds, invertebrates and small mammals.
The Wildlife Trusts provide some good advice on pond creation here. It is really important to ensure that you provide access for wildlife to the pond – either through a sloping 'beach' or through carefully placed rocks to create easy steps. Varying the depth and edges of the pond provides opportunities for different species. It is also really important to ensure that any planting is carefully considered and sourced to prevent spread of invasive non-native species.
Tree planting can provide a range of benefits, for wildlife, amenity, carbon capture, water management or as a source of fruit and nuts. Mature trees provide the greatest benefits to wildlife, but immature trees are still really beneficial and encouraged.
When planting a tree, consider the space available (how big will it get), how quickly it will grow, ground conditions (does it like being on wet ground) and what you want from the tree (shade, colour, berries, fruit, nuts). Use native species and locally sourced plants where possible.
Photos from NHBS and RSPB as illustrations, similar suitable boxes are available from other reputable retailers.