An abundance of life in unexpected places

By | Science & Technology
Arachnids come in many shapes and sizes and include spiders, scorpions and harvestmen.Credit@wikipedia,flickr.com

Typically ecosystem services and biodiversity are mainly associated with natural ecosystems. Yet a recent study, to be published in the upcoming issue of Ecological Engineering, suggests that industrial and post-industrial sites provide refuge for a range of species that may otherwise be ousted from the neighbouring cultural habitat. The study looked at the diversity of arachnids (the scientific name for spiders), scorpions and harvestmen.

Currently, industrial and mining sites usually undergo a reclamation process in order to restore them back to their natural state after exploitation; or to make them suitable for other uses such as farming or housing. From the Forestry Reclamation Approach to the Holistic Approach, reclamation usually involves first restoring the topography of the site by filling up deep mines, or restoring topsoil for example, followed by the re-establishment of previously existing natural communities. Heneberg and his team challenge the view of byproduct sandpits, gravel-sandpits and quarrying sites as habitats of low importance and suggest that they may in fact be quite important for invertebrate communities and, more to the point, host many red listed species (species of high conservation concern).

In his most recent work, Heneberg looked at the presence of spiders and harvestmen in active or unreclaimed sand and gravel-sandpits across the Czech Republic. By conducting a pilot study first, the team identified the bases of the sandpits as biodiversity hot-spots, particularly when adjacent to xerothermophilous (aka dry and hot loving) graces and open wetlands. Subsequently, after considering conditions such as rainfall, altitude and succession state (i.e. the natural change of site and establishment of naturally occurring species), 28 sites of various ages were selected and pitfall traps (small open top containers, buried in the ground aiming to trap falling insects) were positioned appropriately.

A spider, of the order Aranea,  spinning its web Credits @Brenda Clarke

A spider, of the order Aranea, spinning its web. Credit@BrendaClarkeViaFlickr

The study resulted in the sampling of a total of 232 species of spiders and 8 species of harvestmen, with an estimation of 323 spider species actually present in the examined sandpits. The identified species varied in conservation interest based on the International Union for Conservation of Nature (IUCN) red list classification.  In this case 81 species were of conservation concern, with Clubiona pseudoneglecta reemerging in the region after an absence of 55 years and being considered regionally absent.  Of these species 89% were found on unreclaimed sites, of which half were limited to those sites only and 8 species of conservation concern were found exclusively on reclaimed land.

The study reveals that contrary to conventional views, (post-) industrial habitats are dynamic and variable. Interestingly, sites overgrown by trees lacked the characteristic high density of red list arachnid species, due to the loss of the steppe-like conditions that the red list species prefer; and possibly also due to being displaced by species from the surrounding landscapes.  This paper builds on Heneberg’s past research on Hymenoptera, an insect order including bees and wasps, which showed an abundance of species in (post-) industrial sites and the preference of species of conservation concern to said sites. Particularly sand-borrowing species that require loose sand for nesting and take refuge in these artificial habitats, as their natural counterparts are absent throughout the country due to the majority of their land being used for housing or agriculture.

Similar studies have identified (post-) industrial sites as biodiversity hotspots for a variety of organisms, such as butterflies, beetles and ants. Studies also show that industrially created sandpits are starting to be recognized as conservationally valuable for organisms with high migration/dispersal ability. However, it is often the case that mining sites are required by law to be reclaimed to post mining standards. There is a growing number of scientists asking for changes in legislation and alternative restoration strategies, such as natural succession; which is both affordable and may be beneficial for local diversity. In the meantime, more work is necessary to better understand the value of inactive and active quarrying sites.

In addition to the array of conservation services these sites may provide, what other potential use might they have?

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