… a guest blog by Chloe Hardman, (Natural England), Aaron Bhambra and Bailey Carswell-Morris (University of Birmingham).
The problem: a lack of warm, dry, bare soil
If you see a patch of bare soil, you might not immediately think of it as habitat. You might even think, how can we plant it up with wildflowers to make it a better habitat? For a cold-blooded solitary bee however, bare, warm soil can be the difference between life and death.
There are around 240 solitary bee species in the UK. Some are aerial nesters, using plant stems, dead wood, walls and bee hotels, but most solitary bee species are ‘fossorial’, and nest in cavities underground. They excavate tunnels, lay their eggs and provision them with pollen. The developing larvae need dry, warm conditions to grow. If vegetation grows unchecked, this will create shady damp conditions, leading to a lack of suitable nesting sites for solitary bees. Before the British landscape was vastly modified by humans, the soil would have naturally been disturbed by large wild animals digging and trampling, such as wild boar, aurochs (wild cows), wild horses and elk. This process of disturbance also helps restart succession, giving wildflowers the space and light they need to grow, creating open and varied habitat mosaics rather than dark, dense-canopy woodland.
Many of our nature reserves now rely on conservation grazing to replicate the role of wild animals of the past. However, on some sites, conservation grazing is not happening or is not enough to create the right conditions for ground-nesting pollinators. Therefore, site managers need to use diggers or hand tools, to replicate this natural process of disturbance. This can be costly, time consuming and requires a lot of manpower. How can this be done most effectively? How quickly does it make a difference to rare bee species populations? These are questions that our partnership is seeking to answer within the Purple Horizons Nature Recovery Project. The pollinator theme within the project, led by Natural England, brings together local authorities who manage heathland nature reserves, researchers from the University of Birmingham and the Birmingham and Black Country Wildlife Trust.
The project focuses on restoring and connecting habitat within an ancient heathland landscape just north of Birmingham, between Cannock Chase in Staffordshire and Sutton Park National Nature Reserve in Birmingham. We were particularly keen to target efforts towards a Species of Principle Importance for conservation: the Tormentil Mining Bee (Andrena tarsata) known since the early 2000’s to be present in small numbers in this landscape.
Testing solutions: bring out the diggers
With funding from Natural England’s Species Recovery Programme, we were able to start a landscape-scale experiment. We designed a programme of earthworks and floristic enhancements across eight sites, over two years. The work has been carried out with six tonne and eight-tonne mini diggers. We have been creating “bee beaches”, which are patches of bare ground designed to provide nesting and basking sites for solitary bees.
Our work is testing the most effective ways to create and maintain sandy, warm bare ground habitats. Aaron Bhambra and Bailey Carswell-Morris at the University of Birmingham, are carrying out before and after surveys of pollinators on the bare ground patches. Their work includes finding out how bees respond to:
- Variations in slope and the temperature variation this creates
- Variations in soil type and geology (sandstone vs coal measures)
- The creation of new sandy paths
- Soil inversions which expose the rich sandstone layers of geology
We have also been testing the use of green hay and propagation from seed to increase the amount of Tormentil (Potentilla erecta) available for the Tormentil Mining Bee to forage on.
Given that the work is taking place on publicly accessible nature reserves, we have tried to communicate what is happening and why to members of the public, which has included press releases, social media and temporary signage on site. We also made sure to check the historic environment record, get consent for the SSSI works and not impede access on sites that are common land.
The results: rare bees using our newly made habitats
The results have been very encouraging so far. Surveys and records showed that just one rare or scarce pollinator species was found across these eight sites before we started enhancing the habitats. However afterwards, the team found eight rare or scarce species using the sites, including some basking directly on the newly created bee beaches. We know that true population change will take several years to establish, so are seeking funding to continue our monitoring programme to be able to observe this.
Researchers from the University of Birmingham surveyed the sites in summer 2024 and found:
- The Tormentil Mining Bee (Andrena tarsata) nesting and basking on the new “bee beaches”.
- The European Bee Wolf (Philanthus Triangulum) a solitary wasp and the first record for Walsall of this species.
- The Spotted Dark Bee (Stelis ornatula) the rarest bee found in Walsall so far.
- The Noble Jewel Wasp (Hedychrum nobile) a range expanding species new to the West Midlands.
- The Cats Ear Nomad (Nomada integra) and Cats Ear Mining bee (Andrena humilis) two nationally scarce bees found in small numbers throughout Britain.
- The Variable Nomad Bee (Nomada zonata) the first record of this range expanding rare bee in the West Midlands.
We have been finding several new species to the West Midlands, which have moved up from the south of England, and some of which have recently colonised Britain from Europe. One species, the Variable Nomad Bee (Nomada zonata) is a species that only colonised Britain in 2016. Since its arrival, this bee has colonised southern and central England and has moved into the West Midlands. The Variable Nomad Bee is thought to be able to fly over large stretches of water and this may explain its rapid range expansion over the past eight years. Restoring, creating and expanding high-quality habitats is even more important considering this range expansion in response to climate change.
The future
Based on the results of this study, we will be providing site managers at Walsall Council, Staffordshire County Council and Lichfield District Council with advice on how to continue maintaining and creating more bare ground habitat for pollinators. This will include rotational small-scale bare ground creation using the resources they have available; for example, borrowing diggers from other council departments to create more bare ground once a year in winter. We have provided the local authorities with hand tools and greater knowledge, so that they can incorporate digging of small “bee beaches” into their volunteer group work programmes. Walsall Council is set to investigate the feasibility of grazing some of the sites, which we hope could provide a more sustainable method of maintaining bare ground over the coming decades.
With thanks to Walsall Council, Staffordshire County Council, Lichfield District Council the Birmingham and Black Country Wildlife Trust and the UNESCO Black Country Geopark.
Further information
- Buglife Brownfield Guide
- Buglife Heathland Mosaic Guide
- Purple Horizons people-focused blog and nature-focused blog.
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Main Image Credit: Brownhills Common © Aaron Bhambra