Biodiversity discussions tend to focus on visible features such as habitats, protected species, trees and green infrastructure. Yet beneath every woodland, grassland, wetland or river corridor lies an often-overlooked driver of ecological success: geology.
Geology determines soil chemistry, drainage and nutrient availability, which in turn shape vegetation and the species that depend on it. For planners, developers, ecologists and policy professionals, understanding the relationship between geology and biodiversity is central to delivering resilient, policy-compliant development that genuinely benefits the natural environment.
Understanding geology and biodiversity is also part of the practical, evidence-based consideration that influences Biodiversity Net Gain (BNG) metrics, land suitability, mitigation design and long-term ecological resilience.
We investigate why geology and biodiversity are linked and why geological information should be a core consideration in the planning process and BNG decision-making.
Geology and Biodiversity: The Foundation of Every Habitat
Geology refers to the bedrock and superficial deposits that form the physical foundation of the landscape. These materials control drainage, nutrient availability, soil development and landform; all of which directly influence what plants and animals can thrive in a given location.
In ecological terms, geology acts as a primary driver of habitat potential. Chalk, limestone, clay, sand and peat each create distinct environmental conditions that support different assemblages of species.According to Natural England’s Green Infrastructure Guidance, ignoring geology can therefore lead to inappropriate habitat creation, poor ecological outcomes and increased risk to planning compliance.
Planning policy increasingly recognises the importance of place-based environmental understanding, particularly where long-term sustainability and resilience are concerned. The CPRE states that geology provides the starting point for this understanding.
All terrestrial and freshwater habitats are shaped by the physical and chemical properties of the underlying geology. Rock type influences soil depth, pH, moisture retention and nutrient status, which collectively determine what plant communities can establish and persist. Across the UK, many priority habitats exist specifically because of their geology and biodiversity:
- Chalk and limestone geology supports calcareous grassland, one of the UK’s most species-rich habitats, associated with orchids, butterflies and specialist invertebrates.
- Acidic sands and gravels underpin heathland and bog systems, favouring heather, gorse and acid-tolerant flora.
- Alluvial deposits along river valleys create fertile floodplain wetlands and wet grasslands shaped by seasonal flooding.
- Metal-rich substrates give rise to calaminarian grasslands, a UK Priority Habitat supporting the metallophyte plant species that can tolerate them.
Without recognising the links between geology and biodiversity, habitat creation risks becoming superficial: visually green, but ecologically unstable.
Why Geology Has Been Historically Overlooked in Planning
Geology has traditionally been viewed through an engineering or contamination lens rather than as an ecological asset. This is partly because geological features are largely invisible, and partly because responsibility is fragmented across disciplines.
Ecological assessments have historically focused on species and vegetation, while soils and substrates and mineral resources are often addressed later during construction. According to the Construction Industry Research and Information Association (CIRIA) this disconnect can undermine long-term biodiversity outcomes, particularly where habitats are imposed on unsuitable ground conditions.
Geodiversity and Biodiversity
The term geodiversity describes the variety of geological features, landforms and processes. High geodiversity often correlates with high biodiversity because varied physical conditions create a mosaic of niches. This principle is widely recognised in conservation science and is increasingly relevant in land-use planning.
In practice, sites with diverse geology are often more ecologically resilient, able to support species movement and adaptation under climate change pressures. According to the British Geological Survey, this has clear implications for BNG strategy and habitat connectivity.
Policy Context: Geology and Biodiversity
National Planning Policy Framework (NPPF)
The National Planning Policy Framework explicitly recognises geodiversity as part of the natural environment, stating that planning decisions should contribute to conserving and enhancing it alongside biodiversity. This places geology firmly within the scope of material planning considerations in a Local Plan.
Biodiversity Net Gain
BNG requires developments to demonstrate at least a 10% uplift in biodiversity value using the Defra statutory metric to achieve planning permission. While the metric itself focuses on habitat type, area and condition, Natural England guidance stresses that habitats must be appropriate to their location and capable of being sustained in the long term. This implicitly requires consideration of soils, hydrology and geology and biodiversity.
Local Nature Recovery Strategies (LNRS)
Local Nature Recovery Strategies aim to restore and connect habitats at a landscape scale. Geological character underpins these strategies by influencing habitat distribution, water movement, mineral resources and ecosystem resilience.
Climate Change and Geology
Climate change is altering rainfall patterns, temperature regimes and seasonal extremes. Geology plays a key role in determining how landscapes respond to these changes.
- Free-draining substrates may be more resilient to increased rainfall.
- Clay-rich areas may be more vulnerable to drought cracking or surface run-off.
- Peat soils are sensitive to drying and erosion, with implications for carbon loss.
The UK Climate Change Committee states that incorporating geological understanding into planning and BNG strategies helps deliver climate-resilient habitats that can adapt over time.
Soil: A Living System
Soil is one of the most biologically diverse environments on Earth, hosting complex communities of fungi, bacteria and invertebrates essential to nutrient cycling and plant health. Despite this, soils are frequently treated as inert construction materials during development.
Common practices such as long-term stockpiling, compaction by machinery and importing inappropriate soils can significantly reduce soil biodiversity and function according to CIRIA. These impacts directly affect the success of habitat creation and restoration.
Soil resources
According to the Status of the World’s Soil Resources report, the majority of soil resources are in a very poor, poor or fair condition; 33% of land today is degraded to different levels by erosion, salinisation, acidification, compaction and chemical pollution. Further loss of productive soils and mineral resources could lead to reduced crops and the effects of that, but sustainable soil management can avoid this and protect vital ecosystems.
Environment Agency research into the state of soil found that this key natural capital resource is under threat from compaction, erosion and intensive agriculture. The findings conclude that steps must be taken to manage England’s soils sustainably by 2030.
Geology, Water and Climate Resilience
Geology plays a critical role in controlling groundwater flow, surface water movement,, mineral resources and floodplain function. These relationships are increasingly important as climate change alters rainfall patterns and increases both flood and drought risk, according to CIRIA.
Geology-informed design supports:
- Effective Sustainable Drainage Systems (SuDS) that reflect infiltration capacity and groundwater conditions.
- Wetlands that are hydrologically sustainable during dry periods
- Natural flood storage on permeable alluvial soils
A Geology-Led Approach
For planners, developers and consultants, integrating geology and biodiversity into the planning process involves:
- Early-stage geo-environmental and soil assessment alongside ecological surveys
- Designing habitats that reflect natural substrates and hydrology
- Retaining natural landforms where possible
- Viewing soils and made ground as ecological assets rather than constraints
- Aligning BNG delivery with LNRS priorities and geological character
This approach supports compliance with Local Plan requirements, improves BNG outcomes in line with Defra and Natural England guidelines and delivers more resilient ecosystems.
The Changing Approach to Geology
Historically, geology has been seen as a constraint rather than an opportunity in planning. Ecological assessments have focused on existing habitats and species, sometimes without fully considering the physical processes that sustain them.
However, policy drivers such as BNG, nature recovery networks and climate adaptation are shifting this perspective and changing Local Plan requirements. Natural England recognises that long-term ecological success depends on aligning biodiversity goals with geodiversity realities.
Understanding geology and biodiversity can help to:
- De-risk planning applications
- Strengthen ecological assessments
- Improve BNG delivery success
- Support sustainable land-use decisions
- Reduce long-term management costs
- Demonstrate Local Plan policy compliance
For planning authorities, it provides confidence that planning applications are based on full environmental facts. For developers, it reduces uncertainty in the planning process and the likelihood of costly redesigns or enforcement issues.
Geology and Biodiversity Led Planning
Geology may be hidden beneath our feet, but its influence on biodiversity is profound. Rock shapes soil, soil shapes vegetation, and vegetation shapes ecosystems. In the context of the UK planning process and BNG, geology is not an optional consideration, it is a foundational layer of evidence.
As policy increasingly demands measurable, lasting environmental outcomes, understanding and respecting geological context will be essential in planning applications. By putting geology back into the heart of ecological thinking, we can deliver developments that are not only policy-compliant, but genuinely nature-positive.
