One size does not fit all: Recognising Pedodiversity

Pedodiversity: The Hidden Variation Beneath Our Feet

Just as the concept ‘biodiversity’ reflects the natural variation among individuals within a species, so does the concept ‘pedodiversity’ reflects the variation among soil.

Soil is both one entity- yet is found in countless unique forms that continuously evolve with time.

This intrinsic heterogeneity has long been recognised and formalised through classification frameworks such as the World Reference Base for Soil Resources (WRB) and The USDA soil taxonomy. Nevertheless, even within these broad taxonomic groups, soil exhibits substantial variation, which determines the capacity (the inherent potential of soil) to perform essential functions, provide soil services, and buffer against threats to soil.

As the soil is inherently heterogeneous, how it responds to environmental events or management interventions can also vary.

Thereby different soil cannot be expected to perform in the same way.

This is the idea that ‘one size does not fit all’. 

Why Soil Capacity and Condition Both Matter

Complementary to capacity is soil condition which reflects the immediate state of the soil. Both natural processes and anthropogenic activities can alter the soil condition to deviate from its capacity. In this way, capacity can be seen as a useful benchmark to determine the condition of the soil.

The inherent and dynamic attributes of soil are conceptualised within soil security as two distinct biophysical dimensions: capacity and condition.

Soil security is therefore grounded in a soil-centric philosophy that emphasises both the enduring potential and the immediate functionality of the soil, guiding evidence-based strategies for their sustainable management and long-term protection.

A new danger: soil diversity loss

At the current pace of land use change and urbanisation, we are losing soil diversity. This may not always be immediately visible, yet carries profound implications. Reflecting the well-established importance of biodiversity, pedodiversity and biodiversity are strongly correlated at the global scale: countries with high pedodiversity also tend to exhibit high biodiversity.

The loss of soil diversity thus poses a direct threat to broader ecosystem diversity, as declines in pedodiversity can undermine the capacity of ecosystems to support and sustain biological diversity thereby exacerbating other global challenges.

Rethinking soil ‘health’ narratives

Unlike conventional soil assessments that prioritise soil ‘health’ primarily in terms of biomass production, such approaches often emphasise maximising productivity without fully accounting for the soil’s inherent capacity. This narrow focus can lead to overexploitation of soil, where gains in yield come at the expense of other vital soil functions.

Over time, intensive cultivation may enhance short-term productivity while simultaneously degrading other functions such as nutrient cycling, water regulation, and consequently the unique services it provides for that ecosystem.

A truly sustainable approach requires that soil be evaluated holistically, recognising the trade-offs among multiple functions and acknowledging that soil cannot be expected to respond uniformly to management practices.

Current narratives of soil health often reflect human-centric perspectives, emphasising aboveground outcomes that align with our perceptions of a “healthy environment”. However, such views may obscure the critical processes occurring beneath the surface.

This is why the capacity of the soil to perform all its functions is needed as a baseline or reference to determine the soil condition. There we can have a better idea of true soil ‘health’ in response to any change made to the soil. 

What does this mean for soil management?

Pedodiversity must be considered in land use change, integrated in soil management practices and recognised in any effort in soil regeneration or restoration. A critical consideration is determining the reference state to which the soil is being restored.

Soil management and restoration must be tailored to the inherent properties and capacities of specific soil, rather than imposing a universal standard. In this way, soil with naturally low functional capacity can still be considered ‘healthy’ when they operate within their ecological limits.

Conclusion: One size does not fit all

Soil differs inherently in their functional capacities, therefore, a soil with lower capacity should not automatically be regarded as unhealthy. Rather, each soil fulfils a distinct role within its ecosystem, contributing functions that are context-specific and valuable in their own right. 

For when we respect soil capacity, we can maintain the soil to its full potential.                                 

Related Articles