Fly ash deposits, by-products of coal combustion produced around energy power stations, have been found to serve as an alternative home for many insect species, new research shows.

Fly ash refers to the fine silica material that rises with the gases produced during combustion. In the past, this material was simply released into the atmosphere. However, this practice raised many environmental and health concerns and prompted laws aimed at reducing such emissions. With stricter pollution control, fly ash needs to be captured and large deposits now accumulate outside every power plant scattered across Europe.

These deposits have many characteristics in common with natural sand dunes, including fine grain material prone to movement and extreme fluctuations in daily and annual temperatures. However, while sand dunes have become a highly endangered habitat, fly ash deposits are commonplace.

"When I saw pictures of ash deposits, the habitats resembled me natural sands so much that I decided to survey them", said Dr Robert Tropek, entomologist from the Department of Ecology and Conservation Biology, Institute of Entomology in the Czech Republic and lead author of the new study, appearing in the June issue of Biological Conservation.

In their research, two separate fly ash deposits were surveyed and over 3000 bees and wasps were identified, belonging to 227 different species. Surprisingly, four of the species found were considered extinct, while 13 critically endangered, 22 endangered and 33 vulnerable species. It is safe to assume that a reasonable part of these extinct or endangered species moved to secondary habitats in an attempt to ensure their survival, and without fly ash deposits, at least some of them would be gone by now.

"We had some indication that it could be an important refuge because we had several anecdotal records of interesting insect species in several ash deposits. But even I, as an optimistic supporter of post-industrial biodiversity, did not expect that the conservational potential for bees and wasps would be so tremendous", said Dr Tropek.

However, fly ash deposits represent a risk for human health, as they contain mercury, arsenic and toxic substances, which can lead to serious conditions such as fibrosis or even lung cancer. To eliminate this problem, entrepreneurs and engineers are looking at new ways to use fly ash as base material for preparing various compounds, from cement to fertiliser.

This may be good for the environment, but it's fatal for the recently established communities, particularly those originally specialising in drift sands, about 10% of the species identified, which means they have found an exclusive new home in fly ash deposits and cannot survive anywhere else.

"Now, it is necessary to find a solution compromising both human health and vanishing insects conservation. Maybe preserving only small patches of bare ash protected from wind erosion? Or find some other way to prevent wind erosion?" suggested Dr Tropek. "I am an optimist and believe that sooner or later we will start with effective restoration of natural habitats, using species found in post-industrial refuges to re-colonize newly restored plots. This is a good reason to preserve these deposits".

Dr Martin Knovicka, co-author in the study, added: "The great diversity of wild wasps and bees show that for conserving such species, close collaboration with energy business is the only way, as it is more realistic, in this moment, than e.g. deregulating rivers, reinstalling sand storms and having wildfires raging all across Europe."