Why Countries Are Tearing Down Dams Instead of Building Them

What happened?

Dam removal has become one of the more active fronts in river conservation, with Europe and the United States both continuing multi-year programmes to dismantle ageing, often obsolete barriers. Dam Removal Europe, a coalition of conservation groups, has reported that European countries removed a record number of barriers in recent annual counts, concentrated in France, Spain, Sweden and Finland, while the United States has continued a decades-long trend of dam removals, most notably the completion of the largest dam removal project in US history on the Klamath River along the California-Oregon border.

The shift reflects a change in how governments and utilities weigh the costs and benefits of small and mid-sized dams, many built decades or even centuries ago for milling, flood control or hydropower that in many cases is no longer economically significant relative to the ecological and safety costs of maintaining ageing structures.

Key points

• Dam Removal Europe has documented thousands of barriers removed across the continent over the past decade, with annual totals continuing to rise.
• The Klamath River dam removal project, completed after decades of advocacy by tribal nations including the Yurok and Karuk, is the largest dam removal effort in US history.
• The EU’s Nature Restoration Law includes a target to restore at least 25,000 kilometres of free-flowing rivers across member states by 2030.
• Many dams targeted for removal are small, ageing structures no longer used for their original purpose but that continue to block fish migration and sediment flow.
• American Rivers, a US conservation group, has tracked over 2,000 dam removals nationwide since the 1990s.

What we know

Government and NGO data show a consistent long-term trend: dam removal rates have risen steadily in both Europe and North America since the early 2000s, driven by a combination of ageing infrastructure reaching the end of its safe operational life, growing recognition of the ecological costs of river fragmentation, and, in some cases, dedicated public funding for restoration. The EU’s Nature Restoration Law, which entered into force in 2024, formally set river connectivity targets for the first time at the bloc level, giving member states a binding framework alongside funding mechanisms.

In the United States, the Klamath project involved removing four dams and has already shown measurable early ecological responses, including salmon returning to river reaches they had been blocked from for over a century, according to monitoring conducted by tribal, state and federal agencies. American Rivers and the US Army Corps of Engineers maintain databases tracking the scale and pace of removals nationally.

Background

The twentieth century saw a global boom in dam construction, driven by demand for hydropower, irrigation and flood control. Many smaller dams built for milling, local water supply or minor hydropower generation became functionally obsolete as industries relocated, technologies changed, or the dams simply aged past their designed service life without triggering major maintenance investment. By the early 2000s, engineers and safety regulators in both Europe and the US had identified a growing population of ageing dams posing safety risks disproportionate to their remaining economic benefit.

Ecological research over the same period built an increasingly strong case that river fragmentation was a major driver of freshwater biodiversity decline, with migratory fish species such as salmon, sturgeon and eel particularly affected by blocked access to historic spawning grounds. The World Wide Fund for Nature’s Living Planet Index has repeatedly identified freshwater species populations as declining faster than terrestrial or marine species globally, adding scientific weight to restoration advocacy.

Detailed analysis

The economics of dam removal have shifted meaningfully over the past two decades. Maintaining an ageing dam to modern safety standards can cost more than removing it, particularly for small structures that generate negligible power or no longer serve their original purpose, and dam owners — often local governments, utilities or private landowners — increasingly face liability concerns that make removal financially attractive relative to continued maintenance. In several cases, including parts of the Klamath project, dam removal was ultimately driven by the utility company's own cost-benefit analysis showing that relicensing and retrofitting the dams for modern environmental standards would be more expensive than decommissioning them.

Ecologically, results have generally been positive but not uniform. Rivers with dams removed frequently show measurable recovery in fish populations, sediment transport and water quality within a few years, though the scale and speed of recovery depends on factors including the size of the dam, duration of blockage, and the condition of upstream and downstream habitat. Some restoration ecologists caution that removal alone does not guarantee recovery if other stressors — pollution, water abstraction, invasive species — remain unaddressed.

Politically, dam removal has occasionally proven contentious, particularly where local communities value reservoirs for recreation, water storage or flood buffering, or where removal costs are borne by public budgets rather than dam owners. The Klamath project required decades of negotiation among tribal nations, state governments, the dam’s utility owner and federal regulators before removal proceeded, illustrating that even well-supported restoration projects can face lengthy institutional and legal processes.

Why it matters

River restoration through dam removal represents a rare area of environmental policy where ecological, safety and, in many cases, economic incentives point in the same direction, making it one of the more tractable conservation interventions available to governments facing broader climate and biodiversity pressures. Restored rivers can also improve resilience to climate-driven flooding by allowing more natural floodplain function, an increasingly relevant consideration as extreme rainfall events become more frequent in many regions.

For indigenous and tribal communities in North America in particular, dam removal projects such as Klamath carry significance well beyond ecology, representing the restoration of cultural and subsistence practices tied to salmon runs that had been disrupted for generations.

What happens next?

The EU’s Nature Restoration Law will require member states to submit national restoration plans, likely accelerating further dam removals and river reconnection projects across the bloc through the remainder of the decade. In the US, American Rivers and partner organisations are expected to continue identifying candidate dams for removal, with funding support from federal infrastructure and environmental programmes, though the pace will depend on continued political and budgetary support.

Monitoring of the Klamath River’s ecological recovery will continue to be closely watched internationally as a large-scale case study, potentially informing similar large-dam removal debates elsewhere, including on rivers in France and the Balkans where large hydropower dams remain contentious.

Insight Media Opinion

Insight Media Opinion: Dam removal is an unusually encouraging environmental story precisely because it does not require a heroic act of collective sacrifice — in many cases, it is simply cheaper and safer than the alternative, and the ecological benefits arrive as a welcome bonus rather than the primary justification. That combination of incentives is rare in environmental policy and worth highlighting as a template for other restoration efforts.

Policymakers should be careful, however, not to treat dam removal as a substitute for addressing the other pressures on freshwater ecosystems — pollution, over-abstraction and invasive species chief among them. A free-flowing river choked with agricultural runoff is still a degraded river. Removal is a necessary step in restoring many waterways, but it should be paired with continued investment in water quality and habitat management if the ecological gains are to be sustained over the long term.