This wetland site was formerly a lake known as Hockham Mere.  It is now a 'Site of Special Scientific Interest', an SSSI.  This site is special because of the pollen and plant remains preserved in the 9 metre depth of peat and sediment below.  Studies of the tree pollen trapped in the layers of peat of the old lake bed of Hockham Mere have revealed the changing climate and vegetation of Breckland since the last Ice Age and samples from this site form one of the international datum sources.  

 
First came the Birch forests of the cold tundra, followed by warmer periods when Pine and Hazel dominated, then the temperate Oak forests of historic times.  Extensive radiocarbon dating has established that samples from Cranberry Rough provide a time line stretching from 12620 to 1620 bp (bp is 'before present') so from approximately 12680 BC to 1680 BC. 

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This area was once the site of a large lake, left by the retreating glaciers of the last Ice Age 10 -12,000 years ago.  For the neolithic hunters, 10,000 years ago, to the people of the medieval Manor of Hockham, the lake would have been a vital source of fish and fowl.  There are records of a ‘fish house’ here in 1380. 

In Tudor times there was still a large lake, of around 280 acres, called Hockham Mere (probably about the size of the 1932 Flood Boundary shown above), but it gradually silted up and by 1737 it was simply a swamp.

The passion for land improvement in the 18th century resulted in a network of drains criss crossing the swamp. By the end of the century Cranberry Rough had become fully drained agricultural land used for grazing and reed cutting.  Since then man has made repeated attempts to keep the land drained and productive, but by 1920 it was, once again, a swamp; grazing was abandoned and tree seedlings began to establish and invade the open fen.

In 1932 the flooding was so bad that the railway line (now disused), had to be substantially raised.

Ultimately, the lack of success in keeping the drains properly maintained has meant that wetland species have survived and now thrive here.  With its designation as an SSSI in 1961, the emphasis switched instead, to preserving the wetlands as a valuable, and increasingly rare, habitat for the rich variety of plants, insects and birds found here.

In the open areas to the east of the site and along the open drains, many species of reed and sedge grow, including the nationally rare Narrow Small-reed.  Reed and Sedge Warblers make their nests here.  On the open waters of the drains, Little Grebe, and waterfowl such as Shoveler, Gadwall and Tufted Duck are known to breed here.  In summer, dragonflies, damselflies and the beautiful White Admiral butterfly are here in abundance. 

This is the only Breckland site for Royal Fern and Cranberry

On the driest margins of the site the fen vegetation gives way to Soft Rush and tussocky grasses, with Meadowsweet, Milk Parsley and Purple Loosestrife.  In June Southern Marsh Orchid may be found here too.  Beneath the invading alders and willows, carpets of Sphagnum moss remain amongst the pools.  Cranberry, Royal Fern and Cotton-Grass are found here.