Report

Sustainable Asset Valuation of Mining Closures in Artisanal and Small-Scale Gold Mines in Marmato, Colombia

Nature-based infrastructure’s role in mining closure plans

This Sustainable Asset Valuation (SAVi) examines how nature-based infrastructure (NBI) interventions like reforestation, slope stabilization, and hydrological restoration can strengthen mine closure plans in Marmato, Colombia. For every USD 1 invested in progressive closure with NBI, the region gains USD 1.44 in return while also reducing exposure to landslide risk, water contamination, and ecosystem degradation.

By Nathalia Niño, Andrea Bassi on April 24, 2026

Download from NBI Global Resource Centre

Key Findings

Starting mine closure early delivers stronger results at lower cost. For every USD 1 invested in progressive closure, the region gains USD 1.44 in return, a conservative estimate, as several social and health benefits could not be monetized.
The most significant benefit of closing a mine properly is protecting human life. Reducing exposure to landslides, rockfalls, and tunnel collapse is where the economic case for structured closure is strongest.
When mines close without structured rehabilitation, contaminated land, unstable slopes, and degraded ecosystems remain. NBI interventions such as reforestation, slope stabilization, and hydrological restoration reduce risks, restore land, and benefit surrounding communities.

Marmato, in the department of Caldas, is one of Colombia's most historically significant gold-mining territories, where artisanal and small-scale gold mining has shaped local livelihoods and cultural identity for centuries. But mining in Marmato also carries serious risks. Steep hillsides, unmanaged waste, water contamination, and the near-absence of structured closure planning have left the territory exposed to landslides, ecosystem degradation, and long-term environmental liabilities.

Colombia's regulatory framework for artisanal and small-scale mine closure is still emerging. Most mining areas in Marmato currently lack approved closure plans, meaning environmental risks accumulate without a clear pathway for remediation. The NBI Global Resource Centre applied the SAVi methodology to evaluate three closure pathways: a baseline scenario in which mines are abandoned without intervention; a comprehensive closure plan implemented at the end of mine life; and a progressive closure plan in which stabilization, rehabilitation, and NBI measures are implemented gradually during operations. The quantitative analysis is based on a pilot assessment of a representative artisanal mine, with results intended as indicative rather than definitive.

The results show that mine closure in Marmato is fundamentally a risk-reduction investment. Avoided mortality risk—linked to reduced exposure to landslides, rockfalls, and tunnel collapse—represents the largest share of monetized benefits. The progressive closure plan outperforms end-of-life closure: for every USD 1 invested, the region gains USD 1.44 in return—a conservative estimate, as several social and health benefits could not be monetized due to data limitations. Earlier implementation reduces costs by making use of materials generated during operations rather than purchasing external inputs at the end of mine life, and allows risk reduction and ecosystem service benefits to accrue sooner.

NBI plays a central role in this performance. Reforestation, slope stabilization, soil remediation, and hydrological restoration contribute ecosystem services, including erosion control, carbon sequestration, and biodiversity recovery, and reinforce the long-term effectiveness of closure outcomes.