Robert Hawkes discusses some of the early findings of his PhD project, exploring the multi-taxa consequences of landscape-scale management.
Despite many conservation successes over the past 30 years, most efforts have either focused on generic ‘habitat management’ or on a small subset of well-known and charismatic species (often birds and mammals), while neglecting other less well-known organisms (particularly invertebrates). One method developed to address this knowledge gap and allow more effective allocation of conservation efforts, across a larger number of species, is a process called ‘Biodiversity Auditing’. This method, as its name suggests, identifies how many species are present within a region and which should be prioritised before systematically analysing their management requirements.
The Biodiversity Audit approach was pioneered in the Breckland region of eastern England (Dolman et al, 2012), an area characterised by its sandy soils and semi-continental climate. The audit demonstrated that within the regions semi-natural grass-heaths, bare-open ground habitats support a wealth of important species. Over the past few decades, the suitability of these internationally important sites has deteriorated due to the loss of dynamic processes that historically created these conditions (e.g. rabbit grazing, turf removal, mineral extraction, and episodes of arable cultivation; see Figure 1). While it is possible to mimic these historical processes using physical ground disturbance, it is unclear how wildlife will respond and whether certain techniques are more effective than others.
Figure 1: Union Heath, STANTA, in 1996 (top) and 2017 (bottom), illustrating the decline in rabbit populations and the associated loss of bare open micro-habitats. Images courtesy of RSPB and Peter Feakes.
A landscape-scale experiment
The Stanford Training Area (STANTA) contains approximately half of the grass-heath remaining in Breckland (3,500ha) and contains several species which are seldom found elsewhere (such as the threatened dung beetle, Diastictus vulneratus), making this unique landscape one of the UKs most important wildlife sites. Historically STANTA was dug over by rabbits (farmed in warrens) and grazed by livestock until it resembled a shingle beach. However, from the 1980’s the rabbit population declined, dense grassland dominated (see Figure 1). Bare-ground was only found on localised areas of military activity (e.g. trench digging, shelling) and 16 man-made plots managed for breeding Stone-curlew Burhinus oedicnemus. Due to its size, and thanks to the availability of conservation funds through Higher Level Stewardship (HLS), STANTA presented a unique opportunity to trial bold and innovative management techniques on a landscape-scale, something rarely possible on nature reserves. This has enabled one of the UKs largest field experiments, with the aim to determine the multi-taxa consequences of different ground disturbance techniques (Figure 2).
Ground disturbance management started in 2015 and comprised of two establishment methods (shallow vs deep cultivation, both created using agricultural machinery) across 66 plots, plus 40 undisturbed controls (to determine what happens when you do nothing). Disturbance was repeated in early 2016 and 2017. Of the managed plots 26 were maintained as 2 ha homogenous plots treated annually in the same location. The remaining 40 were diversified by cultivating a partially-overlapping 2 ha section each year, thus developed a complex-mosaic of subplots that differed in disturbance history and fallow age. By trialling different methods of establishment (deep-cultivation vs shallow-cultivation) and different levels of plot complexity (homogenous vs complex-mosaic), we hope to establish whether prescription type matters.
Given our existing knowledge of their ecological requirements, positive responses were anticipated for two bird species of conservation concern (Woodlark Lullula arborea and Stone-curlew) plus large numbers of scarce, rare, and threatened invertebrate species. The latter include some species which are found nowhere else in the UK. Confirming this would encourage more widespread uptake across other sites. For other species, such as Eurasian Curlew Numenius arquata, the potential impact was unclear. Since 2015, the University of East Anglia (UEA), in partnership with Defence Infrastructure Organisation (DIO), the Royal Society for the Protection of Birds (RSPB) and Natural England (NE) have been monitoring this experiment through a PhD project. Unlike other field experiments, which generally focus on a restricted component of biodiversity (often birds), this research focused on birds, plants, beetles, true bugs, spiders, bees, wasps, and ants, providing an exceptionally broad and detailed assessment of biodiversity outcomes.
Figure 2: Before (a) and after (b) treatment establishment, showing 5/66 plots, plus one of the historic Stone-curlew plots. Images courtesy of Google maps and Bing maps.
Multi-taxa consequences of ground disturbance: The results so far…..
A bit more detail….
- Woodlark – Woodlark numbers have increased three-fold on the plots since their establishment thanks to the bare-open feeding habitat this management created.
- Stone-curlew – Prior experience, and monitoring since the plots were established, confirmed Stone-curlew used areas of bare ground for nesting. However, it was unclear whether they would also use ground disturbance plots for feeding. Preliminary data from five GPS-tagged birds suggests that recently-disturbed plots were selected in preference to the surrounding grassland, highlighting the value of these treatments.
- Eurasian Curlew – Monitoring by UEA MSc student Natalia Zielonka demonstrated that shallow-cultivated plots (but not deep-cultivation) were selected as nesting habitat, despite covering only c.8% of the grass-heath area (from 36 nests across two years, 14 were on plots with 11 on shallow-cultivated plots). However, productivity was extremely low (30 nests failed at egg, 2 deserted, 3 failed at chick stage, and only 1 fledged a chick). Nest cameras showed that foxes were the main predator, suggesting a need for greater predator control and/or nest protection measures. Interestingly, one nest was predated by sheep, and a crow took an egg from an unguarded nest.
- Invertebrates and plants – When the treated plots were first established (2015), they immediately increased the densities and richness of scarce, rare, and threatened invertebrate species, compared to undisturbed grass-heath controls. Subsequent sampling two years on (2017) has revealed an incredible 194 species of plant and 765 invertebrate species (comprising 410 beetle, 112 spider, 121 true bug, 22 ant, and 100 bee and wasp species); These include Meioneta fuscipalpa, a rare money spider (Linyphiidae) previously known from only one other site in Britain, and Arocephalus languidus (leafhopper, Cicadellidae), a new species to Britain. This information will reveal: 1) optimal management approaches across these different groups, and 2) the benefits and biological costs of physical ground disturbance.
Applying the evidence
The Biodiversity Audit quantified the potential importance of physical ground disturbance; this experiment experimentally confirms its value in the real world. Since management was applied on a landscape-scale across a range of different soil and vegetation types, the results will be applicable to other chalk grassland, grass-heath, and lowland heathland sites beyond STANTA. This ground-breaking (pun-intended) experiment shows what can be achieved by bold and innovative management on large Defence Infrastructure sites when HLS funding is available to pay for conservation work.
Acknowledgments
Paul Dolman, Jen Smart and Andy Brown are Robert’s PhD supervisors. This research wouldn’t have been possible without the help of taxonomic experts (Steve Lane, Doreen Wells, Nick Owens, James McGill, Colin Lucas, Anna Jordan, Tony Irwin, Pip Collier, Tim Pankhurst, Peter Lambley, Richard Carter, Rhys Green, and the Natural England Field Unit), plus three Masters students (Amanda Ratier-Backes, Katie Marsden, and Natalia Zielonka). The Ministry of Defence, Landmarc, Sheep Enterprise, Richard Evans and NE are thanked for their engagement and access. We also thank Peter Feakes, Jacki Crickett, Norman Williams, Gavin Chambers, Bernard Pleasance, and the rest of the STANTA bird group for their assistance, Ian Levett, Dominic Ash, and John Black for their advice and support, and Nigel Butcher, Andrew Asque, and Colin Gooch for technical support. RSPB and NE funded this work through the Action for Birds in England partnership, with support from DIO and Breaking New Ground.
Robert Hawkes is a PhD student at the University of East Anglia, UK. His research investigates outcomes of management to support avian figurehead species for other diverse taxonomic groups (plants, beetles, true bugs, ants, bees, wasps and spiders), utilising one of the largest replicated landscape-scale experiments in Europe.
Email: Robert.hawkes@uea.ac.uk Twitter: @Robert_W_Hawkes
References
Dolman, P. M., Panter, C. J. & Mossman, H. L. 2012. The biodiversity audit approach challenges regional priorities and identifies a mismatch in conservation. J. Appl. Ecol. 49: 986-997
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