The five-banded weevil wasp is one the species said to be under threat
As a legal challenge is launched at the High Court against development on the West Thurrock Marshes, BBC environment correspondent Sarah Mukherjee visits the site.
It's perhaps the weirdest wildlife walk I've ever been on.
A trek along a bramble-tangled footpath in the half light. To the left of us, a huge, brightly-lit factory.
Miles of metal tubing shine like the backdrop to a science fiction film, and the air is full of the smell - bizarrely - of washing powder.
We emerge on another path that leads along the Thames, which looks grey, oily and slow-moving in the early morning light.
We wander past miles of concrete walls, presumably some sort of river flood defence, neon-bright with graffiti.
And then, we come to it. An unremarkable patch of scrubby-looking ground, with a few low trees and a big puddle.
Just the sort of post-industrial overhang that needs a good tidy up, you would have thought.
But according to campaigners at Buglife, this is one of the richest sites for wildlife in the UK.
There once was a power station in this area - but that closed down in the early 1990s, and since then, according to Matt Shardlow, the charity's director, wildlife has taken over that which man had abandoned - until now.
In 2006 Thurrock Thames Gateway Development Corporation gave approval for a development of warehouses on the site, to be used by the Royal Mail.
Buglife started a campaign, saying the corporation had not taken into account the importance of the site to hundreds of rare and endangered species, like brownbanded carder bee, the saltmarsh shortspur beetle, and the humpbacked red ant.
"This is all about the protection of biodiversity," Mr Shardlow says. "Wildlife is important to us - it doesn't matter if it's a tiger or a little beetle, we have to protect it."
The development corporation declined to comment ahead of the judicial review, but has, in the past, pointed out that conservationists had been consulted at all stages of the proposed development, and an environmental strategy had been formulated for the site.
Mr Shardlow said: "The government has passed a law recently that gave a duty to all public authorities to have regard for biodiversity in undertaking their operations.
"In this case, the corporation's decision endangers several species - and we want to try and stop that."
He believes this is the first time that this law has been tested in court, and the decision - whatever it is - could have significant implications for planning law across the country.