The Parish of Felmersham lies within the West Anglian Plain Natural Area, a flat or gently rolling landscape dissected by hawthorn hedges and occasional ancient woods, amidst large tracts of intensively-managed arable land. The plain is drained by the long, meandering River Ouse, which virtually encircles the Parish. The Ouse Valley Way, one of the longest river valley walks in Britain, follows its course, and brings walkers through the parish.

The River Ouse travels from five miles west of Brackley out to the North Sea at King’s Lynn, over 150 miles away. In the past, the Ouse was much wider than it is today, resulting in extensive gravel beds being deposited beneath the fertile flood plains which can now be found along its banks. It was the gravelled terraces on these plains that first attracted settlers to the area and they have continued to shape its landscape across the centuries.

Extensive gravel extraction within the parish in the second half of the twentieth century resulted in the creation of a number of lakes that are now used for fishing and recreation, as well as providing ideal habitat for a host of wildlife. Just outside the Parish, and a popular walk for parishioners, is the Felmersham Gravel Pits nature reserve. The reserve is managed by the local Wildlife Trust and is designated a Site of Special Scientific Interest for its diverse flora, including several species that are rare and declining in the county, and for its exceptionally high number of dragonfly species.

The river itself also attracts a wealth of wildlife: chub, barbel and roach glide through its depths, whilst overhead kingfishers, and the common terns that return to the Parish each spring, scan the water for their next meal. On the grassy flood plains, mute swans gather in large flocks, as do greylag and Canada geese. Coots and moorhens weave through the reeds and vegetation lining the riverbank all year round, whilst in summer the riverbanks echo to the sound of warblers and reed buntings. When conditions are right in spring, the river can come momentarily alive with mayflies, while on still summer days, a variety of dragon- and damselflies fill the riverbank. Less obvious, but a good sign of the health of the river nonetheless, are the otters that appear to have returned to the River Ouse after many years of absence.

Muntjac deer – descendants of escapees from Woburn Park where they were introduced in the early Twentieth Century – are a regular sight around the Parish, as are hedgehogs and, less frequently, badgers and foxes. The churchyard of St Mary’s Church is also home to a variety of wildlife, notably woodpeckers and finches by day and tawny owls by night. Barn owls can also be seen hunting around the Parish and red kites have become a common sight over the old cricket field.