Ponds which provided a breeding ground for protected species and other rare wildlife have been poisoned with dumped diesel and destroyed by industrial machinery.
Smallford Pits has been designated as a Local Wildlife Site, which identifies it as a crucial location for wildlife in the county and protects it from development by the planning system.
The site has also been identified as a breeding ground for great crested newts, a European Protected Species, and is also an important area in Herts for dragonflies.
Smallford Pits supports 19 species of dragonfly, including the nationally rare Scarce Emerald Dragonfly. Only Kingsmead near Hertford, supports as many dragonfly species in the county. The area is also rich in birds and reptiles.
Last September the ponds on the site were completely dug out and scrub cut to the ground. Then in December the ponds were polluted with either petrol or diesel which had been dumped into the water.
The police and Environment Agency investigated the pollution as a wildlife crime, but the Crown Prosecution Service decided not to take any action.
Then last week a JCB turned up and levelled the plant life, which neighbours believe has caused further damage to the environment.
Christine Pedder, who first reported the pollution, said: "I have enjoyed the ponds for many years and loved seeing the amazing wildlife in and around them.
"Why do we have environmental laws if this is ignored? This has set a precedent and if this is not prosecutable then what is?"
Neighbour Dawn Hudson added: "It is so sad and upsetting to see this vandalism of wildlife habitats."
Local resident Steve Brooks works for the Department of Life Sciences at the Natural History Museum. Over 2020 he surveyed the dragonflies at the site, and identified 19 different species, of which at least 16 were breeding.
Steve said: "It's so sad to see this wonderful wildlife site so badly damaged. It's the last thing we need at a time of biodiversity crisis. Places like this are so unusual in Hertfordshire, a truly wild site managed by a herd of ponies. A bit like a mini-New Forest on the edge of St Albans."
County councillor for Colney Heath and Marshalswick, John Hale, responded to the vandalism: "I am very angry at what appears to have been the deliberate destruction of a wildlife site, at a time when we are all being encouraged to protect such sites. We need to be encouraging wildlife, not destroying it.
"Given this latest activity, it is extremely disappointing that the CPS were not prepared to proceed with action after the earlier vandalism, as it effectively gave a green light to more destruction of the habitat."
Matt Dodds, planning and biodiversity manager at Herts and Middlesex Wildlife Trust, said: “It’s devastating news that one of our most significant wildlife-rich sites has been subjected to these actions which has destroyed the habitats of the species that depend upon it.
"We are living in a biodiversity emergency and we cannot afford to lose vital wild places like Smallford Pits that are home to such a diversity of life.
"We are very dismayed at CPS’s decision not to progress a prosecution in this case. Vulnerable Local Wildlife Sites, like Smallford Pits, and their wildlife will continue to be at great risk unless the CPS takes a stronger line on wildlife protection.
"They need to send a clear message that damage to the habitats of protected species is a crime and will not be tolerated or they risk the law being treated with contempt."
A spokesperson for the Environment Agency said: “Following reports of suspected pollution we sent an officer to inspect two ponds at Smallford Pits. These lie within a Site of Special Scientific Interest (SSSI), designated by Natural England.
“Our officer found minimal traces of oil in each pond which were degrading naturally, no clean-up was required. There was no evidence to identify where the oil came from."
The owner of the land is believed to be a company called Colney Smallford Ltd, based in Milton Keynes. No phone number or email is available for contacting them to comment on their plans for the site.
If a member of the public is concerned about a suspected environmental incident they should phone the Environment Agency's free 24-hour incident hotline on 0800 80 70 60.
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