Waste land or 'brownfield' sites are vital for wildlife

Urban wasteland (c) photolibrary.com Bare patches of land warmed by the sun can create a "wasteland mini-microclimate"

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Wasteland or "brownfield" areas are vital but overlooked habitats for UK wildlife, according to the charity Butterfly Conservation.

These sites are home to unusual, hardy plants and their patches of bare ground become warm "microclimates".

Experts say these features allow many rare insects to thrive.

One moth, the small ranunculus, which disappeared from the UK before World War II, has now recolonised brownfield habitats throughout England and Wales.

Winged wasteland residents

Small ranunculus (c) Les Hill/ Butterfly Conservation

The conservation group and and the wildlife magazine the insect journal Atropos are encouraging people, where safe and legal access is possible, to explore their local quarries, disused railway lines, gravel pits and spoil tips in search of unusual moths this weekend.

This call for public participation is part of the charity's annual "moth night".

Richard Fox from Butterfly Conservation said that many of the sites were under threat from by redevelopment and "bland landscaping schemes".

He explained to BBC Nature why these areas - of disturbed or even contaminated land - were such unique habitats.

"An old spoil tip [for example] would be terrible if you wanted to create a garden, but it's great for wildlife, because the poor soil leads to slow development of diverse plants."

The diversity arises because only hardy plants can grow in such poor soil. These "tough" wild flowers - such as rosebay willowherb, prickly lettuce and dandelions - thrive precisely because they are not pushed out by swathes of more common weeds that need a more nutrient-rich landscape.

The variety of wild flowers provides some favoured food for the caterpillars of unusual moth species, such as the small ranunculus. This species disappeared from Britain completely in the mid-20th Century, but has now recolonised large areas of south-east England, become established in south Wales and been sighted as far north as Lancashire.

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Patches of bare ground that heat up in the sun also produce "little microclimates" on brownfield sites.

Mr Fox explained: "These are great for insects, especially in a cool, damp place like Britain."

Elephant hawkmoth (c) Shane Farrell/ Butterfly Conservation Elephant hawkmoths are commonly found on brownfield sites

He added that he hoped "moth night" would encourage formal wildlife surveys of brownfield areas, so that their true environmental value could be calculated and taken into consideration in any decision about whether and how to develop them.

Philip James, professor of ecology at the University of Salford, agreed that such sites could be ecologically important, telling BBC Nature that they often became home to rare species "normally associated with other habitats that are regularly disturbed, such as river banks, sandy heaths or chalk grassland".

But rather than avoid developing brownfield sites all together, he pointed out that it was important to understand their changing nature, and perhaps to leave areas derelict when they harboured "the greatest species richness".

"Over a few years," Prof James explained, "soil begins to build up and the vegetation changes.

"Before the soil builds up and burrowing animals come in is when there are opportunistic plants and the insects that feed on them.

"That is the time when... one might find nationally rare species."

Prof James suggests that these "transient" habitats could become part of planning an ever-changing, rich urban landscape.

Disused quarry (c) Jim Asher/ Butterfly Conservation Disused quarries can be home to many wildflower species

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