Restoring Forest Ecosystems on Opencast Mines

Restoration in a hostile environment

Retaining neither remnant vegetation nor top soil, mines are the most hostile environment (Stage 5 degradation), where FORRU-CMU has performed research to restore forest ecosystems Since 2010, our unit has collaborated with the Siam Cement Group (SCG), to develop techniques, aimed at 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/ball clay mine (Mae Tan) and a semi-opencast limestone quarry (Muang Poon).

Mae Tan Lignite and Ball Clay Mine (2010-14) - “Technical Assistance to the Siam Cement Group for Re-vegetation of Mae Tan Mine”

This project provided training to SCG staff and developed methods to re-establish functioning, biodiversity-rich forest ecosystems on an extensive opencast pit, as production of lignite and ball-clay came to an end. Project activities included:

• A survey of nearby remnant forest (reference forest) - to set restoration targets and locate tree seed sources.
• Establishment of a phenology study trail and training of SCG staff to collect data and initiate seed collection.
• Training SCG staff in tree propagation techniques in the mine's tree nursery, to improve planting stock quality.
• 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 biodiversity recovery in restoration plots.
• Analyses of phenology, field-trial data and a database of tree species.

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 greening up of the restoration plot - but there's still many bare patches. The 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) - "Forest Restoration and Biodiversity Monitoring in a Limestone Quarry, Chae Hom District, Lampang Province"

In this project, SCG continued to partner with FORRU-CMU to work on restoring forest to decommissioned sites within the first pit (of three) of a "semi-opencast" limestone quarry. Started in 2012, the project supported the transformation of depleted mine terraces into biodiverse ecosystems. Project activities included:

• Baseline biodiversity studies: comprehensive surveys documenting plant and bird species, in conservation forest to be retained within the mine concession.
• Establishment of 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 on forest ecology, seed collection, nursery management, experimental design and monitoring techniques.

The results and findings were promising.

• A combination of treatments, resulted in the highest performance of planted trees: supplementary top soil, NPK fertilizer and addition of effective micro-organisms (EM). Cardboard mulch mats also had positive effects.
• Promising framework species: several native species demonstrated outstanding potential as "framework species." Gmelina arborea, Bombax ceiba and Bischofia javanica 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. 

Some of the more successful species that displayed framework-species characteristics at the SCG Muang Poon Mine, 9 months after planting: circled in orange: Bauhinia purpurea (already flowering); blue: Bischofia javanica, red Gmelina arborea and yellow: Alstonia scholaris.

With the selection of appropriate species, the addition of imported top soil and the application of fertilizer and cardboard mulch mats, canopy closer was achieved within 3 years, under the harsh conditions of this post-mining site.

The results from surveys and experiments were compiled into a booklet on how to perform forest restoration on mines.

During this project, we began to observe the exceptional value of planting fig trees (Ficus spp) on quarry sites. Their expansive root systems crack open the quarry substrate, allowing the entry of water and oxygen, necessary for soil formation. Furthermore, their highly edible figs attract seed-dispersing macaque monkeys into the restoration plots from the adjacent conservation forest The project created opportunities for two of our MSc students to work on Ficus trees for mine reclamation: Watit Khokthong and Nuttipon Yabueng Left: Ficus trees started to produce figs within three years after planting, which attracted seed-dispersing macaque monkeys (right) from adjacent forest onto the restoration plots - building potential for recovery for forest-tree-species diversity.

Phase 2 (2017-2020) - "The Biodiversity Management Plan (BMP)"

The second phase of the project with the Muang Poon mine centered around planning how to manage biodiversity across the mine concession area, which comprised not only the pits, but also a considerable expanse of relatively intact remnant bamboo-deciduous forest, which the company retained as "conservation forest". FORRU-CMU assisted with developing guidelines for managing existing biological resources, restoring biodiversity on reforested sites and biodiversity offset. Click here  or access via the download panel.

Phase II project activities included:

• Monitoring the progress of existing restoration plots and identification of appropriate quarry rehabilitation techniques to serve as a model.
• Rehabilitation of new post-mining areas using local species and techniques refined from Phase 1 (e.g., terracing, adding soil, planting at 500 seedlings/rai and testing polymer gel and compost).
• Conducting new surveys on the biodiversity status in restoration sites, conservation forest and sites not yet mined (pits 2 and 3).
• Establishment of a database on the phenology of local plant species and the morphology of seeds and seedlings for important species.
• Ultimately pooling all experience and experimental results to compile a Biodiversity Management Plan (BMP) for the entire concession area, aligned with international standards.

Mae Tan Lignite and Ball Clay Mine (2025-28) - "Biodiversity Management Planning on a Lignite and Industrial Clay Mine"

The BMP for the Muang Poon mine was well received by SCG, and so the management of the Mae Tan mine requested a similar study, which started in December 2025.The 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.This time, the FORRU-CMU crew is teaming up with a multidisciplinary team of CMU-Biology-Department experts in botany, community engagement, amphibians and reptiles, hydrology, aquatic ecosystems and ornithology to build a comprehensive plan, which integrates forest restoration with the wider environment. The FORRU-CMU team kicked off the study with a survey of community forest (as the reference forest ecosystem) on the outskirts of the concession area. CMU Environmental Science student, Khin Saw Htay (2nd from right) has adopted this work for her MSc thesis project.