Why nature cannot be replaced: the limits of substitution in biodiversity conservation

Dominique Ghijselinck

Contemporary conservation governance increasingly relies on biodiversity offsetting and related instruments that seek to compensate ecological losses from development projects through metric-based equivalence and No Net Loss accounting. In their dominant policy form, these approaches treat biodiversity as substitutable: damage at one site is rendered acceptable if equivalent gains are generated elsewhere. This paper examines the limits of this substitution logic. Drawing on literature on biodiversity offsetting, value pluralism and conservation governance, it argues that metric equivalence cannot by itself establish the substitutability of nature. Biodiversity embodies not only instrumental benefits but also intrinsic and relational values that resist fungibility. These values are difficult to represent within exchangeable metrics. Substitution therefore depends on two reductions: plural values are narrowed to measurable benefits, and complex ecological systems are simplified into indicators that can be compared across sites and over time. To clarify the governance implications of these limits, the paper develops an Ethical Impact Assessment framework centred on a plural-value scaffold linking ecosystem structure, functions, services and value dimensions. This scaffold shows why compensatory responses vary in ethical reach depending on the level of ecological organisation at which they intervene. Where compensatory equivalence cannot plausibly justify harm, the framework introduces a justificatory exit: a decision point at which projects threatening non-substitutable ecological values should be reconsidered rather than balanced through offsets. Recognising these limits reorients conservation governance toward stronger avoidance, restraint and forms of ethical repair that acknowledge irreversible loss without presuming replacement.