The granting of these top habitat accolades to sites in London and Birmingham shows just how important urban greenery has become to beleaguered wildlife.
"Nimby" campaigns saved them from being smothered in houses as the cities expanded earlier this century. Now they provide a refuge for declining species as well as refreshing millions of human visitors.
National Nature Reserve status brings prestige, stronger protection from any threat of development, and a better chance of attracting public and private sector grants for improvement works. English Nature, the Government agency which designates the reserves, says the two new urban sites would qualify even if they were in deep countryside, because of their richness of species and habitats and the excellent prospects for preserving them.
But the reserves' proximity to the city also exposes them to fly-tipping and vandalism.
Ruislip Woods, on the north-west fringe of London, was officially declared a National Nature Reserve yesterday. Covering just over a square mile, the woods are home to seven of the 14 bat species found in the British Isles and a recent survey found more than 500 different species of fungi.
Three sides of the woods are bordered by Metroland suburbs - Pinner, Ickenham, Ruislip, Northwood - while the fourth faces the Green Belt. The bulk of the woods had been owned for more than four centuries by King's College, Cambridge but in the 1920s Middlesex County Council bought them to stop them being built on.
Today the woods, with their green woodpeckers and woodcocks, are owned and managed by the London Borough of Hillingdon under the watchful eye of a Ruislip Woods Trust.
Coppicing has been revived, with the wood sent to make pulp at a paper mill in Gwent. A herd of hardy long horn cattle graze Poor's Field, a meadow on the edge of the woods, to prevent scrub invading the grasses and wildflowers.
Sutton Park, four square miles of ancient woodland, heathland, bogs and a golf course on the north-eastern edge of Birmingham, is surrounded by built-up land. It was declared a National Nature Reserve on the last day of March.
It was given to the people of Sutton Coldfield by Henry VIII in 1528, and is owned and managed by Birmingham City Council. More than 2 million people visit each year.