Transport Scotland contracted Jacobs to carry out an impact assessment for a major road widening project in Scotland. The assessment found that new woodland would need to be planted to compensate for habitat lost to the scheme, and soil translocation was proposed to help the new woodland establish.

Before translocation, Jacobs needed a clear baseline of what lives in the soil. NatureMetrics used soil eDNA to survey four habitats, detecting almost 3,000 species across bacteria, fungi and soil fauna. The results clearly separated grassland from woodland soils, defining what the woodland creation must achieve. The data will guide which soils are moved, and will track whether the new woodland becomes ecologically equivalent to the woodland lost.

Soil biodiversity is a vital part of land ecosystems and a strong indicator of habitat type and condition. But it’s notoriously hard to survey.

Soil organisms are small and poorly known, and experts can usually identify only some groups. Surveying them with traditional morphological methods is slow, expensive and often impossible. Bacteria and many fungi can’t realistically be surveyed this way at all.

Jacobs needed a rigorous, cost-effective way to:

• Characterise soil communities across the woodland likely to be affected and the grassland where new woodland will be created
• Set a baseline for monitoring the compensatory habitat
• Compare woodland soils to inform the translocation strategy
• Find the most effective method for surveying soil fauna

• Soil eDNA across four habitats: NatureMetrics analysed 80 soil samples from ancient birch woodland, non-ancient birch woodland, coniferous plantation woodland and a grazing pasture where new woodland will be created.
• Multiple groups, one sample set: bacteria, fungi and soil fauna were all characterised from the same field samples.
• Simple field collection: on-site teams collected samples using NatureMetrics field kits. Laboratory analysis and bioinformatics were then completed centrally.
• Method comparison: we compared direct soil eDNA with bulk mesofauna samples, where animals are first extracted from soil using heat and then analysed. This showed which method gives the best picture of soil fauna.
• Comparing groups: we tested which taxonomic groups best separate habitats and track restoration.

• Almost 3,000 species: soil eDNA detected almost 3,000 species-level taxa across bacteria, fungi and soil fauna.
• Grassland vs woodland: grassland soil communities were significantly different from the woodland likely to be affected by the scheme, with lower fungal and faunal richness.
• Consistent signals: fungi and fauna showed very similar patterns across habitats, adding confidence to the results. Bacteria were slightly less informative but still differed significantly between woodland and grassland.
• Birch woodlands were similar: ancient and non-ancient birch woodland did not differ significantly. This could widen the choice of woodland soils for translocation, although more sampling is needed to confirm it.
• Direct eDNA outperformed traditional extraction:
  • Heat-extracted soil fauna yielded only around 10% of the species found by direct soil eDNA.
  • It was strongly biased towards arthropods such as beetles, mites and springtails, and missed major groups such as nematodes entirely.
  • The direct method was also cheaper and carried less risk of samples being lost between laboratories.

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A clear baseline and target
Jacobs now knows exactly how grassland and woodland soils differ: the gap the woodland creation needs to close. Success can be measured by how far the grassland soil community shifts towards the woodland baseline.

Better translocation decisions
Jacobs can objectively compare woodland soils to choose the best ones to move. Translocating the right soils could speed up the new woodland’s establishment.

Long-term, measurable monitoring
Repeat sampling in future years will track how soil communities recover against the baseline and control sites. This gives quantitative evidence of restoration progress.

Lower cost, lower risk
Direct soil eDNA delivered the baseline at lower cost than the traditional two-step method, with less risk of losing samples, and captured far more species.