How to manage biodiversity impacts using the mitigation hierarchy
When it comes to managing your organisation's biodiversity impacts, not all strategies are equal. The mitigation hierarchy provides a decision-making framework that has become the global standard for responsible environmental management. ISO 17298 makes this hierarchy central to biodiversity action planning, requiring organisations to follow its sequence: first avoid impacts, then minimise unavoidable impacts, then restore degraded ecosystems andfinally – only as a last resort – consider biodiversity offsets for truly residual impacts.
This isn't just environmental best practice – it's increasingly becoming regulatory requirement, investor expectation and stakeholder demand. Organisations that master the mitigation hierarchy position themselves for both better biodiversity outcomes and stronger business performance.
Understanding the hierarchy
The mitigation hierarchy is sequential and preferential. Each step has declining effectiveness for biodiversity, so you must exhaust options at each level before moving to the next.
Avoidance prevents impacts before they occur by changing what you do or where you do it. This is always the most effective and often the most cost-efficient approach. Avoided impacts don't need mitigation, restoration or offsetting.
Minimisation reduces the magnitude, extent, duration or intensity of unavoidable impacts. When you cannot avoid an impact entirely, minimise it as much as technically and economically feasible.
Restoration rehabilitates degraded ecosystems on-site after impacts occur or remediates ongoing impacts at their source. This includes ecological restoration of affected habitats and regeneration of ecosystem functions.
Offsetting compensates for residual impacts that cannot be avoided, minimised or fully restored by creating biodiversity gains elsewhere. Offsets are controversial, complex andshould only be considered after genuinely exhausting other options.
Avoidance
Avoidance strategies fundamentally redesign activities to prevent impacts. A mining company might relocate a planned facility away from critical habitat rather than developing within it. A infrastructure developer might reroute a road to avoid fragmenting wildlife corridors. An agricultural company might source from regions where land conversion isn't required rather than driving deforestation.
Product redesign can avoid impacts throughout the value chain. Substituting sustainably sourced materials for those driving habitat loss avoids upstream impacts. Designing for durability and repair avoids waste-related impacts. Eliminating toxic substances avoids pollution impacts.
Avoidance isn't always obvious. It requires asking fundamental questions: Do we need to do this activity at all? Could we meet our objective differently? Is this location appropriate? Could alternative technologies or processes eliminate this impact?
Early consideration is crucial. Avoidance options shrink once commitments are made, infrastructure is built or contracts are signed. Build biodiversity assessment into site selection, investment decisions, product development and strategic planning so avoidance opportunities aren't foreclosed by premature decisions.
Minimisation
When impacts cannot be avoided, minimise them through improved practices, technologies and management.
Spatial minimisation reduces the geographic extent of impacts. Minimise facility footprints, concentrate infrastructure rather than fragmenting landscapes, create buffer zones around sensitive areas and use vertical rather than horizontal expansion where possible.
Temporal minimisation adjusts timing to reduce impacts. Schedule construction outside breeding seasons, avoid critical migration periods, work during times of day that minimise disturbance and phase activities to allow ecosystem recovery between impacts.
Technical minimisation employs better technologies and practices. Low-impact equipment reduces disturbance, precision agriculture minimises chemical applications, efficient processes reduce resource consumption and waste and pollution control technologies reduce emissions.
Intensity minimisation reduces impact severity. Lower speeds reduce wildlife collisions, dimmer lighting reduces ecological light pollution, quieter operations reduce noise impactsand gentler practices reduce ecosystem stress.
The key is achieving maximum feasible reduction. "Feasible" considers both technical possibility and economic reasonability, but economic constraints cannot justify inadequate minimisation when cost-effective options exist.
Restoration
Restoration addresses impacts that occur despite avoidance and minimisation efforts. ISO 17298 defines ecological restoration as "activity or process that assists in initiating or accelerating the recovery of an ecosystem that has been degraded, damaged or destroyed."
On-site restoration rehabilitates affected areas. Revegetate cleared areas with native species, restore hydrological connectivity to wetlands, remove invasive species, recreate habitat structures like nesting sites and rebuild soil health through organic amendments.
Remediation addresses ongoing impacts at their source. Treat polluted water before discharge, capture emissions before they enter the atmosphere, remediate contaminated soilsand repair fragmented habitats through wildlife corridors.
Effective restoration requires ecological expertise. Successful projects are based on understanding ecosystem dynamics, using appropriate native species, recreating necessary habitat structures, addressing underlying degradation causes and allowing sufficient time for ecosystem recovery – which often spans years or decades.
Set realistic restoration objectives. Complete restoration to pre-impact conditions is often impossible, but significant ecosystem recovery is usually achievable. Focus on restoring critical ecosystem functions, supporting key species and reconnecting fragmented habitats.
Offsets
Biodiversity offsets compensate for residual impacts by conserving or restoring biodiversity elsewhere. ISO 17298 positions offsets at the end of the hierarchy for good reason – they're the least certain, most complex and most controversial option.
Legitimate offsets require several conditions. They must deliver measurable biodiversity gains beyond what would have occurred anyway (additionality). They must be ecologically equivalent or superior to lost biodiversity (equivalence). They must persist at least as long as impacts persist (permanence). They must be verified and transparent.
Many claimed "offsets" fail these tests. Simply funding existing protected areas doesn't demonstrate additionality. Creating new habitat of different type than destroyed habitat doesn't achieve equivalence. Short-term projects offsetting permanent impacts don't satisfy permanence.
The standard's emphasis on exhausting avoidance, minimisation and restoration before considering offsets reflects growing recognition that offsets often fail to deliver promised benefits. Some impacts – like extinction of species or destruction of irreplaceable ecosystems– simply cannot be offset.
Avoiding impact transfers and displacement
ISO 17298 includes a critical caution: ensure that actions to avoid or reduce impacts "do not produce other significant impacts that adversely affect the environment." This warns against impact transfers and displacement.
Impact transfer occurs when solving one biodiversity impact creates a different impact. Reducing water pollution by sending contaminated water to hazardous waste disposal transfers the impact rather than eliminating it. Replacing one harmful input with another harmful substance transfers rather than solves the problem.
Impact displacement occurs when avoiding impacts in one location causes them elsewhere. Protecting habitat in one area while intensifying harmful practices in another location displaces rather than reduces impacts. Sourcing from a different region to avoid local impacts may simply export the problem.
Avoiding transfer and displacement requires systems thinking. Consider full life cycles, examine displaced activities' destinations, account for broader landscape effects and ensure solutions genuinely reduce total impacts rather than moving them around.
Practical implementation
Apply the mitigation hierarchy systematically to each material impact identified in your assessment. For each impact, document avoidance options considered and explain why chosen. If avoidance isn't feasible, document minimisation measures implemented and explain why further reduction isn't possible. If impacts remain after minimisation, detail restoration plans. Only after demonstrating genuine effort at prior steps should offsets be considered, with rigorous standards for equivalence, additionality and permanence.
This documentation serves multiple purposes – it supports internal decision-making, demonstrates due diligence to regulators and stakeholders and creates accountability for following the hierarchy genuinely rather than symbolically.
From hierarchy to action plan
The mitigation hierarchy isn't theoretical – it's an operational framework that should directly shape your biodiversity action plan, which Article 8 will explore in detail. Organisations that internalise the hierarchy's logic make better decisions, achieve better biodiversity outcomesand often discover that avoiding and minimising impacts costs less than remediating and offsetting them. Most importantly, they contribute to genuinely reversing biodiversity loss rather than simply attempting to compensate for it.
