The nature reserve is managed primarily for bird conservation, particularly through control and improvement of wetland, heath and grassland habitats, with particular emphasis on encouraging nationally uncommon breeding species such as the bittern, stone-curlew, bearded tit, marsh harrier, nightjar and nightingale.

[3] From 500 BC to 700 AD, the sea level in Suffolk was about 6 m (20 ft) higher than it is today, and the low-lying areas of the present coast were then tidal estuaries.

[7] Ranulf de Glanvill, King Henry II's Lord Chief Justice, founded a Premonstratensian abbey on the marshes at Minsmere in 1182.

[8] The lower section of the chapel was built soon after the demolition of the abbey in 1363, and the brick upper parts are thought to have been added by former abbot John Green, who lived there as a hermit when he retired from his post in 1527.

The reeds that grew there were cut for thatching, and access was improved by using sand from the higher alluvial areas to build tracks across the marshes.

[14] These marshes were enclosed and drained for agricultural use in 1812 and 1813,[15] following the passing of the relevant Act in 1810,[16] with the main sluice being built to control drainage to the sea.

The canal was used to transport the thatch crop inland by barge, its bridges being built particularly high to enable the bulky cargo to pass beneath.

[23] The RSPB had been considering the Minsmere site, at that time about 600 hectares (1,500 acres) in extent,[5] as a potential reserve from the late 1930s, and a management agreement was signed in 1947.

He realised that ecological succession would eventually lead to the loss of important habitats, such as bare ground on the heaths or open water in the reed beds, unless natural plant colonisation was actively prevented.

Many areas were reforested, but it was noticed that other badly affected woodlands nearby were colonised by woodlarks, so some recently acquired arable land was acidified and converted to heathland to encourage open-ground species.

[23] The Minsmere reserve covers about 1,000 hectares (2,500 acres) of reed bed, open water, lowland heath, grassland, scrub, woodland, dune and shingle vegetation.

Coastlink, a demand responsive bus service, is available from these places to travel to the reserve but requires booking a day in advance.

RSPB Minsmere is accessible on foot from Dunwich Heath, Sizewell Beach and Eastbridge, and there are 19 kilometres (12 mi) of public rights of way around the reserve.

The visitor centre provides a café, picnic area, shop, toilets and baby-changing facilities; guided walks, binocular hire and children's 'explorer packs' are also available.

[36] The heathland and acidic grassland areas of Minsmere are managed by grazing, heather and scrub control and removal of trees and unwanted western gorse.

[37] Methods used to acidify the land, which had been arable farmland for 150 years, included grazing by sheep[38] or the addition of sulphur, either with bracken and heather waste,[39] or on its own, followed by reseeding.

Creation of ditches and pools and better water-level management led to 9–12 males being present annually, and application of these techniques elsewhere has revived the fortunes of this species in the UK as a whole.

Other important species are bearded tits, woodlarks, nightjars in open habitats, nightingales in the woodlands, and Dartford warblers, which returned to Minsmere's heaths in the mid-1990s, having been lost to the area six decades earlier.

[23] Many wildfowl winter on the reserve, including wigeon, gadwall and teal, and easterly winds can bring in passage migrants, sometimes in large numbers.

Notable recent occurrences include Great Britain's first western swamphen in 2016,[41] a black-browed albatross in 2015,[23] pallid harrier and collared pratincole in 2014,[42] and Audouin's gull and red-flanked bluetail in 2011.

[43] Mammals found at Minsmere include a herd of about 300 red deer, otters, badgers and water voles,[23] the last being protected by active control of introduced American mink which have led to major declines elsewhere.

[44] Other vertebrates include adders, small numbers of natterjack toads and 13 species of fish, of which common rudd is an important food source for bitterns.

[46] The shingle ridges on the beaches hold a variety of uncommon plants including yellow horned-poppy,[47] red-tipped cudweed and round-leaved wintergreen.

[48] Minsmere faces threats from rising sea levels, caused by climate change, which adversely affect the drainage of the reserve and can lead to river flooding.

[50][51] An article written on behalf of the RSPB suggested that any damage to the wetlands at Minsmere is likely to have a major effect on UK bittern numbers since the reserve holds a significant proportion of the national breeding population.

[45] In 2018, expansion plans for Sizewell were called into question by National Infrastructure Commission proposals to scale back the nuclear power programme on safety and environmental grounds.