Restoring Forest Ecosystems on Opencast Mines

Mining presents the most hostile environment, where FORRU-CMU has attempted forest ecosystem restoration (Stage 5 degradation), having neither remnant vegetation nor top soil. Since 2010, our unit has collaborated with the Siam Cement Group (SCG) at two mines in Lampang Province, to develop restoration techniques, capable of restoring forests and biodiversity under the extremely harsh conditions that prevail, when mines are decommissioned and returned to nature.

Our collaboration has centered around two mines in Lampang Province: a lignite mine and a semi-opencast limestone quarry:

Mae Tan Lignite and Ball Clay Mine (2010-13) - developing restoration techniques

This project, titled “Technical Assistance to the Siam Cement Group for Re-vegetation of Mae Tan Mine”, provided training to SCG staff and developed methods to re-establish functioning, biodiversity-rich forest ecosystems on an extensive opencast pit, as lignite and ball-clay production came to an end. Project activities included:

• A survey of forest tree species in and description of nearby remnant forest (reference forest).
• Establishment of a phenology study trail and training of SCG staff to collect data and initiate seed collection.
• Training SCG staff in propagation techniques to diversify and improve the quality of planting stock, produced in the mine's tree nursery.
• Field trials to compare performance among tree species and to test the effectiveness of various sylvicultural treatments
• Establishment of a monitoring system for planted trees and recovery of biodiversity in planted areas and training SCG staff to use it.
• Analyses of phenology, field trial data and a database of tree species, provided to the company.

Restoring forest ecosystems on abandoned opencast mines is slow going. Left 2010 - a young restoration plot at the Mae Tan mine. Right (2025) shows a dramatic rise in the reservoir water level and general greening up of the restoration plot - but there's still many bare patches. This project provided an opportunity to our MSc student Farzana to work on her thesis project testing direct seeding on the mine. Farzana, Nuttira and Golf  collecting data from direct seeded plots at the Mae Tun SCG Mine 2010. The seeds were placed in blue PVC tubes to keep track of them. Muang Poon Mine (Lampang Cement)   

Phase I (2012-2016) 

In this project SCG continued to partner with FORRU-CMU to work on restoring forest to decommissioned sites within the first phase of a "semi-opencast" limestone quarry. Started in 2012, the project supported the transformation of depleted mine terraces into thriving, biodiverse ecosystems, setting a new standard for sustainable industrial practices in the region. Project activities included:

• Baseline biodiversity studies: comprehensive surveys documenting plant and bird species, both on the mine and in surrounding protected forest.
• Experimental restoration plots to test the framework species method of forest-ecosystem restoration. The experiment compared: 1) blasting bedrock versus adding a thick layer of topsoil and 2) applying chemical fertilizer (NPK) versus fertilizer combined with effective microorganisms (EM).
• Knowledge transfer and training: through workshops and field sessions, FORRU-CMU transferred knowledge on forest ecology, seed collection, nursery management, experimental design and monitoring techniques.

The results and findings were promising.

• High survival in experimental plots: overall seedling survival after the first rainy season was excellent, averaging 92.55%.
• Plots on blasted bedrock showed superior survival rates (over 99%). However, seedlings planted in added topsoil exhibited dramatically faster growth.
• Promising framework species: several native species demonstrated outstanding potential as "framework species." Gmelina arborea (So), Bombax ceiba (Ngio) and Bischofia javanica (Tem) showed particularly vigorous growth. Notably, some species like Bauhinia purpurea began fruiting within months, a promising sign for attracting wildlife.
• The bird survey documented 53 species in the conserved forest and 30 species in the young restoration area. 

A major output from this project was a booklet on how to perform forest restoration on mines.

Phase 2 (2017-2020)

In this phase, FORRU-CMU together with SCG developed guidelines for managing biological resources, enhancing post-mining area rehabilitation as a best practice model. Majority of work for phase 2 builds on phase 1 which include

• Development of an appropriate Biodiversity Management Plan (BMP) through stakeholder meetings.
• Establishment of key framework guidelines for developing a suitable Mine Closure Plan.
• Creation of a database summarizing the relationship between plant species (phenology) and wildlife resources in the area, in the form of a food web illustrating overall ecosystem relationships.
• Monitoring the progress of restoration plots and summarize appropriate quarry rehabilitation techniques to serve as a model.
• Establishment of a database on the phenology of local plant species and the morphology of seeds and seedlings for important species.
• Conducting new surveys on biodiversity status in restoration areas, conservation forest, and areas not yet mined.
• Rehabilitation of new post-mining areas using local species and techniques refined from Phase 1 (e.g., terracing, blasting, adding 1m of soil, planting at 500 seedlings/rai with polymer gel and compost).
• New experiments to find the minimum soil depth required for planting and to increase species diversity in restored areas to cover at least 40% of the pre-mining forest species.

The main output from this project was the Biodiversity Management Plan (BMP) (available as a downloadable file) that aligned with international standards.

Mae Tan Lignite and Ball Clay Mine (2025-28) - developing a post mining biodiversity management planThe project kicked off on December 2nd 2025 with contract signing at the mine office - our team started surveying forested areas near the mine the same day, by drone and on the ground.