A campaign to reopen a historic railway line on a nature reserve would be "hugely destructive" and not commercially viable, a conservation group has warned.

Railway historian Nathaniel Dodd is appealing to the Department for Transport to reinstate the Alexandra Palace to Finsbury Park line, and has gathered 75 signatures in a petition.

He says bringing back the line, which was opened in 1873, could reduce traffic and air pollution and bring around 300,000 people a year to the venue.

But part of the line - once intended to be integrated into the Northern Line - is now the Parkland Walk Nature Reserve, and conservation group The Friends of Parkland Walk says bringing back trains would be "hugely destructive".

Vice chair Cathy Meeus said there was an outcry in the late 1980s against plans for a major road on the route and the area was designated Metropolitan Open Land as a result, giving it protection from being built on.

The 4km Parkland Walk is now the longest linear nature reserve in London and part of the Capital Ring walking route. 

Cathy said: "For the past 40 years this patch of rural peace in the midst of a densely built-up urban area has provided huge benefits for the physical and mental health of the local community and wider public. It is also well used by cyclists."

She said the Parkland Walk provides a "valuable habitat" for many species of birds and invertebrates and its trees and vegetation are an important element in efforts to mitigate climate change.

"All of this would be lost if a railway were to be built along this route," she added.

"It must be remembered that the previous railway line was abandoned because demand fell away. There are numerous buses that serve this area and a new railway would not be commercially viable, regardless of the environmental cost.

"The aim of the petition is misconceived and, rather than contributing to the environment, would be hugely destructive. Thankfully it is also a non-starter from an economic point of view."

Mr Dodd was approached for comment.