Short communicationIs coal combustion the last chance for vanishing insects of inland drift sand dunes in Europe?

•The bees and wasp biodiversity of two fly ash deposits was surveyed.•Numerous critically endangered species of drift sands were recorded.•Successional overgrowing was revealed as negative for conservation.•Fly ash deposits were revealed to have high conservation potential.

Inland sand dunes rank highly in the most threatened environments throughout Europe, suffering accelerating losses of associated biodiversity. Although there is increasing evidence that vanishing species may find refuges at post-industrial barrens, insects specialised for the highly specific and extreme conditions of drift sands have not been known to colonise any surrogates. Because fly ash deposits share some substrate physical attributes with drift sands, we hypothesised that they could be colonised by drift sand communities. Here, we show that these relatively common landscape structures accompanying coal combustion indeed host insects of extraordinary conservation value. Surveying two fly ash deposits in Central Europe, we found an unusually high diversity of 227 species of bees and wasps, including 72 nationally endangered species (including four thought regionally extinct and 13 critically endangered), and 31 drift sand specialists. This conservation potential seems to diminish with successional overgrowing of the deposited ash. We also document that at the landscape level, the deposits are effectively supplementing the vanishing drift sands. Power-plants producing fly ash deposits, commonly viewed as biotic wastelands, thus paradoxically provide crucial refuges for vanishing biodiversity.