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What is the mitigation hierarchy? Here's what you need to know

Biodiversity is being lost at an alarming rate with hundreds of species becoming extinct every year, orders of magnitude above historical norms.

In response, ICMM members are committed to helping create a nature positive world, pledging to increase biodiversity and boost nature world in objectively measurable and quantifiable ways.

Mining is an important driver of economic growth and is playing a vital part in the world’s transition to green energy, but historically it has often had a detrimental impact on biodiversity. 

To help create a nature positive future, today’s ICMM mining projects are putting nature at the forefront of planning and operations.

The first step on every project is implementing the mitigation hierarchy.

Step 1 – Avoidance

Wherever possible, operations should seek to avoid impacting species and natural processes, especially those that cannot easily recover if disturbed. For example, this could include avoiding the disturbance of important habitats and seasonal breeding grounds.

In northern Sweden, Boliden has adapted its Liikavaara operation at its Aitik site to avoid impacting areas with the highest natural values. The company modelled different layouts of the industrial site and mine deposits to investigate both short and long-term effects.

It determined that the best option was to split the extracted deposits such that any acidifying elements are transported to the main site in Aitik, whilst the environmental rock is managed in situ at Liikavaara. This solution involves a much smaller industrial area and also reduces the risk of pollutants leaching to the natural environment.

Step 2 – Minimisation

Where avoidance isn’t possible, actions such as building wildlife underpasses on roads and measures to reduce noise and dust pollution can enable wildlife to live normally despite the presence of mining operations.

In Mongolia, Rio Tinto is protecting wildlife by adding bird deflectors to transmission lines at its Oyu Tolgoi operation. 

Step 3 – Restoration

When mining at a site or part of a site is complete, good practice is for soil and indigenous vegetation to be replaced to allow biodiversity and ecosystems to regenerate.

In the Highlands of Central Papua, PT Freeport Indonesia has reclaimed more than 472 hectares with native plant species. It has created 463 monitoring plots, each of which is three metres by three metres, to monitor the growth of indigenous vegetation in the reclamation area as biodiversity is restored.

While in Bolivia, Minera San Cristóbal is taking action to rehabilitate areas disrupted by mining activities. It aims to re-establish the traditional use of the soil, thereby preserving the local ecosystems. 

In total, 133 hectares of soils that were affected during construction and operations are targeted for restoration. The work is being carried out in collaboration with a local community-based company.

Step 4 – Offsetting

Any unavoidable remaining impacts after steps 1-3 have been completed are balanced by creating conservation gains elsewhere, to help ensure there is no overall loss of biodiversity. 

Offsets must also target the habitats or species that have been adversely affected and be based upon rigorous methods, transparent methodologies and robust monitoring frameworks, to ensure that offsetting delivers genuine conservation outcomes that are ecologically effective and socially equitable.

In South Africa, African Rainbow Minerals’ Khumani Mine has partnered with the Department of Environmental Affairs and the Department of Nature Conservation in the Northern Cape to establish a biodiversity offset area. 

It has been registered as a conservancy – a protected area for the conservation of nature, including wildlife, plants and ecosystems – helping to ensure its longevity past the closure of the mine.

ICMM members are committed to helping to work towards a nature positive future. The mitigation hierarchy is a fundamental part of this commitment, informing the decisions and actions of all members throughout the life of a mine on how the operation interacts with its surrounding environment.