The Royal Mail is to build a lorry park and distribution warehouse close to a wildlife habitat in Essex.
The Thurrock Marshes site near the River Thames
Permission has been given to build the business park on West Thurrock Marshes, home to hundreds of species of plants, invertebrates, birds and reptiles.
The plan was criticised by wildlife campaigners who said the development would destroy flower-rich grasslands.
Developer Rosemound said it consulted with conservationists and formulated an environmental strategy for the site.
Royal Mail said it would take up less than a third of the 45 acre site.
A spokesman said developers were working closely with Natural England and work was under way to "re-water" part of the site near the River Thames.
It hoped this would encourage back wildlife such as over-wintering birds.
Agreements on conservation
Up until 10 years ago the site was home to a power station and fly ash was disposed there.
Thurrock Thames Gateway Development Corporation has passed a resolution to grant planning permission after a two year consultation period.
But those opposed to the development are upset.
Matt Shardlow, the director of lobby group Buglife, said: "We are extremely disappointed that this destructive development has been approved.
"West Thurrock Marshes should clearly be protected for its wildlife and as a resource for local people."
About 50% of the site will be built on and the rest will be managed in accordance with conservation agreements.
The developer, Rosemound, said: "A management strategy has been formulated which vastly improves large areas of habitat within the site and secures the long term future of these nationally important species."