Why do we want large trees in rivers?

A new river restoration technique to help foster healthier habitats

Why rivers?

Protected, connected rivers generate more food for wildlife and people, support local economies, and keep traditions alive.

Work on the ground

We’re working with Project SHARE to add large wood back in the Narraguagus River.

Why rivers matter in a changing climate

Why do Maine's rivers need to be restored?

Maine’s era of log drives ended in the 1970s but the state’s native fish populations are still suffering the effects of 300 years of those drives, which straightened and widened the river channel creating a river with less complexity. The natural turns and bends in the river that create pools for fish to rest in, gravel bars to spawn on, and the boulders and wood that support the food that fish eat were removed to provide a more efficient path for logs to float downstream.

Despite vast improvements in water quality and increases in fish passage resulting from dam removals and culvert upgrades, the discouraging reality is that Maine’s rivers and streams have lost the complex in-stream structures necessary for healthy riverine habitat. Further, because the necessary building blocks for building complexity like boulders and large trees have been removed, the rivers are “stuck” until those features return which means 100’s if not 1000’s of years.

What is this project aiming to do?

Today a multiyear, multi-partner river restoration initiative focused on improving in stream habitat for sea-run fish for Maine’s endangered Atlantic Salmon, as well as wild native brook trout populations.

The technique involves the felling of large trees into rivers and streams as a way to improve stream function and productivity, cool warming waters, and counteract the detrimental effects of nearly 300 years of log driving.

This – seemingly counterintuitive – new restoration technique involves the felling of large trees into rivers or streams as a way to cool warming waters, improve stream function and productivity, and counteract the detrimental effects of nearly 300 years of logging.

How do fallen trees help restore rivers?

When trees are dropped into rivers and streams, their trunks change the direction of river flow so the water digs deep pools and cause gravel to settle downstream.  This alteration creates ideal conditions for salmon and trout to lay eggs and offers a refuge of deeper and cooler water for fish to rest. The tree branches trap leaves and other organic matter that support aquatic insects. They may even force the river to dig into the bank which increases the amount of rocks and gravel into the river. This approach to habitat restoration – which got its start on the West Coast – offers the potential to improve in-stream habitat and counteract the damaging effects of hundreds of years of log drives. Professionals in Maine are actively studying techniques to implement in rivers in streams in Maine and monitoring the changes caused by these restoration techniques on the creatures in our rivers and stream.

Thank you to all of our partners. Click the logos below to learn more.

FAQs on adding large wood into rivers


1. Are there successful examples of this work happening elsewhere?

This pioneering work originated in the Pacific Northwest and has recently expanded into Vermont, New Hampshire, and Maine. These innovative techniques have been meticulously documented to produce significant shifts in habitat dynamics, including increased pool depth and frequency, enhanced cover for fish, sediment sorting, and improved spawning grounds. River segments treated with these methods have demonstrated an uptick in fish abundance and growth. However, given the relatively short duration and limited scale of these efforts, conclusive evidence regarding their impact on fish population levels remains pending.

Ongoing projects across the nation, including in Maine, aim to comprehensively assess how the introduction of large wood to rivers can bolster the growth, survival, and reproductive success of trout and salmon populations within these waterways.

2. Where is this work happening?

This work is currently underway nationwide, particularly in regions with salmon and trout populations. Numerous state and federal agencies, along with non-governmental organizations (NGOs), are actively engaged in large wood addition projects throughout the state of Maine. These projects span across the Western Mountains, northern Maine, and Downeast regions.

3. What are the long-term goals of this work?

The aim of this project is to restore selected rivers to a state more closely resembling that of their natural condition, akin to how they existed for millennia, and aligning with the ecosystems that fish have adapted to over time. Hopefully through this work, we will bolster fish populations and enhance their resilience to safeguard their long-term survival and productivity.

4. How is this work funded?

This initiative is supported by a combination of grants and private fundraising efforts. State and federal grants from diverse programs dedicated to fish habitat play a significant role in funding these projects. Additionally, this work is supported by contributions from private individuals and foundations.

5. How will this work impact recreation on our rivers?

One major hope for this initiative is to enhance fishing and wildlife viewing opportunities along our rivers. However, all partners acknowledge the potential to inadvertently hinder paddling opportunities and compromise paddling safety. To mitigate these concerns, this work is intentionally avoided in areas frequented by whitewater paddlers. Furthermore, collaborative efforts are in place among partners to educate the public about both the advantages and disadvantages associated with restoring our rivers through the addition of large wood.