Prior to the 1920s, the land was predominantly open moorland, managed for grouse shooting and sheep grazing with remnants of native upland woodland existing along stream sides and in isolated craggy areas.

Forestry England, funded from the public purse, purchased land across the country with the brief of establishing a strategic reserve of timber for the nation.

Since that time, management principles have changed in order to reflect rising awareness of environmental needs and to provide recreational facilities whilst seeking to maintain a sustainable supply of timber.

Sitka spruce (Picea sitchensis) covers 75% of the planted area; this species thrives in the damp conditions afforded by northern Britain.

475,000 cubic metres of timber are harvested annually to supply local sawmilling, chipboard, pulp and wood fuel customers.

Clear-felled areas are replanted with a mix of coniferous and broadleaf tree species; opportunities are also taken to increase the proportion of open space and to improve the riparian habitat.

Due to the low human population and scarcity of roads and railways, Kielder Forest was proposed in July 2016 as one of the preferred reintroduction sites for the Eurasian lynx, which has been extinct in Britain for 1,300 years.

The Castle serves as a hub for the growing number of recreational facilities on offer, walking and cycling trails, picnic areas and a forest drive.

[9] The forest contains a number of art and architectural installations including a Skyspace[10] designed by James Turrell and Wave Chamber, a camera obscura in a stone cairn by Chris Drury.

In 2010, former British distance runner Steve Cram inaugurated the Kielder Marathon which is a circuit around the lake taking in the surrounding gentle contours.

In 2020, an episode of series 11 of Michael Portillo's Great British Railway Journeys featured Kielder Forest, referring to the 1936 Bradshaw's Guide.