Written Evidence submitted by Buglife – The Invertebrate Conservation Trust (SH0095)

About Buglife

Buglife is the only organisation in Europe devoted to the conservation of all invertebrates. Our aim is to halt the extinction of invertebrate species and to achieve sustainable populations of invertebrates.

How can the Government measure progress towards its goal of making all soils sustainably managed by 2030? What are the challenges in gathering data to measure soil health how can these barriers be overcome? 

Soil invertebrates provide a variety of essential ecosystem benefits such as cycling nutrients that plants need to grow, decomposing dead plants and animals so that they can nourish new life, and regulating pests and diseases. They’re also critical for the process of carbon conversion. Soil biodiversity is poorly understood and monitored and must be improved to ensure we know that all soils are sustainably managed by 2030.

We agree with the Soil Association’s call that sustainable soil management practices should be adopted by farmers and land users to prevent and minimize soil biodiversity loss and soil biodiversity must be included in National Biodiversity Strategies and Action Plans[1].

What changes do we need to see in the wider food and agriculture sector to encourage better soil management and how can the Government support this transition? 

Soil must be treated as an ecosystem and vital resource that require restoring, nurturing, and protecting. We must halt extensive exploitation of soils with the notion we can simply top them up with increased external inputs. Policies must minimise soil degradation and protect soil biodiversity, addressing the issues we set out below.

What does UK Government need to do to tackle other stressors on soil health such as soil contamination? 

Pesticides

The use of pesticides causes huge damage to wildlife. They are particularly implicated in pollinator declines caused by neonicotinoid insecticides, but also in the loss of invertebrate life in our freshwater systems. Researchers have found that pesticides harm beneficial, soil-dwelling invertebrates including earthworms, ants, beetles and ground nesting bees[2]. Pesticides can remain in soil for years or decades after they are applied, continuing to harm soil health[3]. Soil quality is greatly improved in areas without chemical use.

As part of a review of pesticide uses, the UK must initiate a full assessment of the environmental risks posed by pesticides to bumblebees, solitary bees, hoverflies, moths, and other insects, but also to groups such as earthworms, beetles, snails and aquatic invertebrates through residues in soil and in aquatic habitats. The assessment must enable the application of the precautionary principle.

The link between advice to farmers and pesticide profits must be broken. Farmers deserve truly independent advice from people who are just as motivated and trained in non-chemical and ecological approaches to managing land for the joint outcomes of producing food and conserving biodiversity.

Domestic pesticide uses and municipal use by Local Authorities must be banned ensuring all soil quality is improvement, not just those of agriculture.

Veterinary Medicines

Veterinary medicines such as those used for both internal and external parasite control threaten soil dwelling invertebrates and can lead to significant pollution of freshwaters.

Insects such as dung beetles are especially sensitive to medicines used to treat parasitic worms[4]. Adult dung beetles tend to be attracted to dung parasiticide residues, but larvae are less likely to occur in the presence of residues. It is thought that larvae that hatch from eggs in areas with residues die early in development. As such, the abundance of adult and larval stages of dung beetles is significantly reduced in dung containing parasiticide residues.

Research has shown detrimental effects on chough populations from the use of medicines for the control of flies, liver fluke and intestinal worms, as they reduce much of the soil fauna on which the chough feed, including flies and beetles[5].

The use of veterinary medicines needs to be reduced and only used as part of a more sustainable suite of treatment and management options.

More monitoring of veterinary medicines needs to be introduced and include substantive responses to environmental risks. Improved environmental risk assessments must be introduced into the approval process for these potentially very harmful substances accounting for impact of soil and freshwater biodiversity.

Invasive Non-Native Species

Invasive Non-Native Species (INNS) threaten the diversity of native soil biodiversity. Non-native soil invertebrates can have dramatic negative impacts on native plants, microbial communities, and other soil animals.

The international trade in pot plants poses a particular threat. Billions of pounds worth of plants and trees are transported around the world every year. They may bring colour to homes and gardens but with them, they bring unwanted organisms in the soil or contained within or on the plants themselves. Species such as New Zealand Flatworm (Arthurdendyus triangulatus) can wreak havoc on native wildlife, while invasive slugs such as the Spanish Slug (Arion vulgaris) can harm garden plants and crops.

Over £1billion of live plants and planting materials are imported into the UK each year. It is currently not possible to ensure all growing media is free from hitchhiking non-native species.

Once introduced INNS can reproduce rapidly, are difficult, if not impossible to eradicate, and pose a risk to native soil invertebrates such as earthworms by feeding on them. There are 5 native species of flatworm in the UK but between 14 and 16 non-native species. Buglife’s PotWatch survey identifies increased reports of non-native flatworms, including multiple invasions of Obama Flatworm (Obama nungara) in north and south England, and shows New Zealand Flatworm to be well spread on Fair Isle, the most distant inhabited island in the British Isles[6].

Non-native flatworms can reduce local earthworm populations by 20% – this could have a huge impact on soil health and agriculture, as well as our native soil wildlife[7]. One species, the New Zealand Flatworm is listed on the Invasive Alien Species (Enforcement and Permitting) Order 2019, as part of retained EU Regulation following Brexit. Three further species of non-native flatworms are included on Schedule 9 of the Wildlife and Countryside Act 1981, which states that it is an offence to introduce or release them into the wild.

Current phytosanitary requirements for plants and growing materials imported into the UK are not fit for purpose and are significantly weaker than the exporting standards required to trade to other nations. Discovering species such as flatworms, ants, snails, and slugs, in soil and potted plant consignments is challenging and time-consuming given their size and range of species. The most suitable preventative measure that can be taken is to end the importation of soils and potted plants containing soil. This measure is taken by other nations to prevent the spread of non-native species and is a requirement of exports from the UK, including to the EU.

Biosolids

The use of sewage sludge as fertiliser is a major driver of soil contamination. This is because contaminants such as microplastics and chemicals (e.g. pharmaceuticals and PFAS) are often present in agricultural sludge and are highly persistent in the environment. The long-term use of sewage sludge in agriculture is known to increase the abundance of antibiotic resistance genes in soil[8].

Pharmaceuticals

Treatment for biosolids are not designed to remove chemical waste and they are known to retain chemical contamination throughout the treatment period for over six months. Most investigated chemicals, including pharmaceuticals such as ibuprofen and diclofenac, have been recorded in activated sludge at very low concentrations. No legislation currently addresses chemical contamination of treated biosolids, resulting in soil contamination as well as leaching into waterways.

Pharmaceuticals can alter soil chemistry and may be taken up by soil organisms such as earthworms. Greater research is required to understand the level of impact pharmaceuticals may have on soil biodiversity.

Leaching of pharmaceuticals from fields treated with biosolids derived from sewage sludge can change dramatically over time. All chemicals act differently in the soil. Long term studies demonstrate the importance of monitoring the changes in chemical concentrations over time as levels of contamination are not static.

Different methods of application can impact the levels of contamination in run off. Injection leads to far lower levels of pharmaceuticals in runoff compared to broadcast application. However, care should be taken so that these different methods do not transfer the problem elsewhere, such as groundwater.

Greater understanding of the impact of pharmaceuticals exists for freshwater species. Studies have shown water polluted with pharmaceuticals to be associated with declines in the abundance of aquatic invertebrate communities.

Measures to reduce loss of pharmaceutical substances into the environment should be developed as part of a cross industry strategy addressing the use of pharmaceuticals as well as removing substances through biosolid and wastewater treatment.

Microplastics in soils 

To date little attention has been given to microplastics in soils.  

Spreading of biosolids on land is estimated to contribute 110,000 and 730,000 tons of microplastics to agricultural soils in Europe and North America per year[9]. In addition, an increase in municipal composting could lead to increased contamination of urban soils. Research has shown that earthworms can transport plastic from the surface into the soil where it may persist for long periods. It is also possible that microplastics may migrate from the soil into groundwater[10].  

Despite this significant contamination of soils, little research has been undertaken into the effects of these microplastics on soil biota. There is however evidence that the activity of earthworms is reduced when they ingest microplastics[11].  

Bare ground & early successional habitats

Exposed soils and bare ground devoid of vegetation are not often considered to be valuable habitats for wildlife. However, bare ground is an essential habitat feature for a wide diversity of wildlife including many plants, lichens, reptiles, birds, and a huge number of invertebrates. Many of the species which require bare ground are unable to survive without it, and a significant proportion of these are rare or scarce.

Vertical, sloping and flat bare ground offers nesting sites for burrowing bees and wasps. The most suitable substrates are sufficiently friable to allow burrowing, but firm enough to prevent burrows collapsing. Bare ground heats up quicker than vegetated ground, providing the warm conditions required by warmth-loving invertebrates. South facing cliffs and slopes are particularly useful for these species. Bare areas are also favoured hunting grounds for visual predators such as jumping spiders and tiger beetles. Specialist ‘pit predators’ such as the larvae of tiger beetles also favour bare ground where they wait in burrows to ambush prey.

Bare ground also provides a germination site for colonising plants. These plants provide valuable nectar and pollen sources for a variety of insects such as the UKBAP listed Red-shanked carder bee (Bombus ruderarius) and Brown-banded carder bee (Bombus humilis). Quarries, due to the impoverished soils, may give rise to extensive swathes wildflowers, providing a super-abundance of nectar and pollen.

The early colonising plants are also the host to many plant eating insects, including butterfly and moth caterpillars. Kidney vetch, the sole foodplant for the Small Blue Butterfly caterpillar (Cupido minimus), is confined to high pH (alkaline) soils as is Horseshoe vetch - the sole foodplant for Chalk-hill Blue Butterfly (Lysandra coridon) and Adonis Blue (Lysandra bellargus). Bird’s-foot trefoil is the foodplant for a number of species including Dingy Skipper (Erynnis tages), Common Blue (Polyommatus icarus), Six-belted Clearwing (Bembecia scopigera) and Chalk Carpet moth (Scotopteryx bipunctaria).

These open habitats were once common in the wider countryside; however, changes in agriculture and an intensification of land use has led to the loss of bare ground features. Sustainable soil management should provide a continuity of such habitats that makes them such important refuges for many invertebrate species that were previously more widespread.

Soil health benefits of flower-rich grasslands

Modern farming methods have contributed to the rapid loss of flower-rich grasslands, with over 97% (an area the size of Wales) having been lost in England since the 1930s[12].

Established wildflower meadows have complex root systems, which makes the soil very stable. This can help improve soil health and prevent loss of nutrients. Wildflower-rich habitats also support some of our most threatened species, with a greater number of pollinators associated with them than any other habitat. By creating more wildflower-rich grasslands we can help wildlife to thrive, while also providing a wealth of other public goods for us all.

The soils in wildflower-rich grasslands sequester carbon and help to combat climate change – some even capture more carbon than woodlands. These habitats also help our farmers, by supporting the pollinator populations that help them grow crops, but also providing a home to the many wasps, flies and other predators that help to control agricultural pests. Livestock grazed on wildflower-rich meadows also have a more varied diet, making healthier animals and healthier food for people.

February 2023