Should Wales Plant Trees on its Coal Tips?

Karen Bishop
2 days ago
5 min read

Disused coal tip at the foot of Graig Fawr. Photo: ©Alan Hughes, Geograph, CC-BY-SA/2.0

If you've spent time in the South Wales valleys, you'll know that the hillsides still bear the marks of more than a century of mining. Yet many of Wales' coal tips have been found to support rare insects, reptiles, fungi and wildflowers. Together these raise an important question: as Wales seeks to expand woodland cover, and investment in coal tip safety accelerates, what role should trees play in restoring former industrial land? The answer is to understand which sites are suitable for woodland creation and which aren't.

Many Former Coal Tips Are Already Valuable Habitats

The nutrient-poor spoil, varied topography and decades without intensive management have created conditions that support an extraordinary range of wildlife. Surveys of South Wales coal tips have recorded more than a thousand invertebrate species, including dozens of conservation priority species and some found nowhere else in the world.[1]

Among them are two millipedes with suitably memorable nicknames. The "Maerdy Monster" was discovered on a former colliery tip in the Rhondda in 2016 and has not been recorded anywhere else since.[1-3] The "Beddau Beast" is a tiny species found on a spoil site in Beddau that, until its discovery in South Wales, had only ever been recorded in the Pyrenees.[2,4] Alongside these are rare bees, lizards, slow worms, seasonal ponds and fungi that have colonised these sites naturally over time.[2,3] This serves as a reminder that restoration does not automatically mean tree planting.

Some sites may be best left as open grassland, heathland or scrub, while others may require active conservation management to protect biodiversity that's taken decades to establish. Any woodland creation programme should begin with rigorous ecological assessment that considers the risk of invasive species; disturbed ground and restoration works can create ideal conditions for plants like Japanese knotweed and rhododendron, which can rapidly colonise sites and outcompete the rare species already present. The goal should not be to maximise tree cover at all costs. It should be to achieve the best outcome for each site.

Safety Has to Come First

Wales also faces a genuine and ongoing safety challenge. In 1966, 116 children and 28 adults were killed when a colliery tip collapsed onto the village of Aberfan. The disaster prompted new legislation, but with more than 2,500 disused coal tips across the country, and as climate change brings more frequent extreme weather, the challenge of making coal tips safe has not gone away. Storm Dennis, in 2020, triggered a major landslip at Tylorstown, blocking a river valley and covering a strategic water main and cycle path. Storm Bert, in 2024, caused a landslip at Cwmtillery that forced residents from their homes.[5,6]

For the communities living beneath and near these tips, this is not an abstract risk. It is something many have experienced first hand. Safety is paramount, and where a tip is unstable, engineering and geotechnical remediation must come first. Trees are not a substitute for stabilisation works, drainage improvements or other safety measures.

Addressing this challenge will require substantial long-term investment and coordination between government, regulators, landowners and local authorities. It is one of the most significant environmental and infrastructure legacies Wales continues to manage.[5,6] This is why woodland creation should be considered alongside the safety programme, not instead of it.

On sites that have been stabilised and assessed as suitable, well-designed woodland can play a valuable supporting role. Trees can help intercept rainfall, reduce surface runoff and slow the movement of water through catchments, contributing to greater resilience for communities downstream. Woodland is not a flood solution on its own, but in the right place it forms an important part of a wider natural flood management strategy.[7] Trees can support both landscape recovery and climate adaptation.

Two Tips, Two Answers

Consider two different coal tips. The first supports a rich and established community of rare invertebrates and reptiles. It sits on stable ground, has developed significant ecological value and shows no history of instability. In this case, the best outcome may be to leave the site largely as it is, with targeted habitat management where necessary.

The second has already required remediation works, supports relatively low biodiversity value and has been assessed as suitable for restoration following stabilisation. Here, woodland creation could be an excellent option, improving biodiversity, increasing tree cover and contributing to wider catchment resilience.

Neither approach is the correct form of restoration. They are simply different answers to different circumstances. Treating every former colliery site the same, whether that means planting all of them or planting none of them, risks losing something valuable.

Restoring Land, Respecting Communities

The legacy of coal mining in South Wales is not only environmental, it's social, cultural and deeply personal. Much of the debate around tree planting centres on productive farmland and grazing land. Yet many former industrial sites are degraded, underused and already earmarked for some form of long-term restoration. In some cases, they offer an opportunity to create new woodland without displacing agriculture or creating new land-use conflicts. Those living alongside these landscapes should be involved in shaping their future from the outset.

Where Things Stand

Investment in coal tip safety has increased significantly. The Disused Mine and Quarry Tips (Wales) Act has established a stronger regulatory framework for the oversight and management of these sites.[6,8]

In January 2026, a new multi-year Coal Tip Safety Grant scheme committed more than £80 million to maintenance and remediation work across more than 400 sites, and the combined Welsh and UK Government funding for coal tip safety now exceeds £230 million.[9] However, important challenges still remain.

Many sites still require detailed engineering assessment before restoration can begin. Others need ecological surveys to ensure valuable habitats are not lost unintentionally. Land ownership is often fragmented. Funding remains constrained relative to the scale of the challenge, and meaningful community engagement takes time and resources.

Success will not come from treating every site the same. Some former coal tips should remain open habitat. Some require engineering intervention before anything else can happen. Some may be suitable locations for new native woodland. All sites require careful assessment, good science and genuine community involvement.

Listening to the Landscape

The question is not whether Wales should plant trees on coal tips. It is how we identify the right sites for woodland creation, protect the wildlife that is already there, improve safety for the people living below and create landscapes that work for the generations who will inherit them. The right answer for each site already exists in the landscape, in the ecology surveys and in the knowledge of the people who live alongside it. The job now is to listen carefully enough to find it.