When you hear the term “old-growth forests”, you may picture vast woodlands filled with towering trees, lush undergrowth and abundant wildlife. These forests are more than just a beautiful sight — they are necessary for sustaining ecosystems and maintaining environmental balance. Old-growth forests are unique ecosystems, developed over centuries, and understanding their importance and impact is crucial. 

Explore what old-growth forests are, why they matter and how you can contribute to their preservation.

What Are Old-Growth Forests?

Old-growth forests — also known as primary forests — are ecosystems that have developed undisturbed by human activities or natural disasters for a long period of time. They are defined by their rich biodiversity, complex structure and resilience. These forests are home to various plant and animal species, some of which cannot thrive in younger, secondary forests.

Key features of old-growth forests include large, mature trees and fallen logs that decompose and return nutrients to the soil and diverse plant species. These ecosystems also feature unique microhabitats — such as tree hollows and deadwood — which serve as homes for numerous creatures.

5 Reasons Why Old-Growth Forests Are Important

There are plenty of reasons why old-growth forests matter — here are five, top ones.

1. Carbon Sequestration

One of the most critical functions old-growth forests perform is carbon sequestration, which involves absorbing carbon dioxide from the atmosphere and storing it. In fact, these forests store more carbon than younger forests. This ability to sequester carbon helps mitigate climate change, reducing the amount of greenhouse gases in the atmosphere. 

2. Biodiversity Hotspots

Old-growth forests are biodiversity hotspots — home to countless species of plants, animals, fungi and insects. A single old-growth tree can host hundreds of species, including rare and endangered ones. Nearly 80% of the world’s terrestrial animals and plants call forests home, with old-growth forests providing some of the most essential habitats.

Species such as the northern spotted owl and the marbled murrelet — both found in North American old-growth forests — rely on these ecosystems for survival. When these forests are lost, the delicate balance of biodiversity is disrupted, leading to potential species extinction.

3. Water Filtration

Old-growth forests are integral to the global water cycle by filtering and purifying water. As rainwater passes through the forest’s layers of vegetation, soil and roots, water is naturally filtered, reducing the need for human-made water treatment systems. 

This natural filtration process ensures rivers, streams, and lakes downstream from old-growth forests remain clean and clear. Notably, forests provide drinking water to over 180 million Americans, with old-growth forests playing a significant role in preserving water quality.

4. Soil Health

Old-growth forests also contribute to soil health. The thick, multilayered canopies protect the soil from erosion by slowing down rainfall, allowing it to seep gently into the ground. Fallen leaves and decomposing logs enrich the soil with organic matter, providing key nutrients for plant growth. This constant cycle of life and decay ensures the soil remains fertile and productive.

5. Climate Moderation

Forests — especially old-growth ones — help regulate local and global climate patterns by cooling temperatures through transpiration, where trees release water vapor into the air. This cooling effect is vital in tempering extreme weather events. Deforestation — including the loss of old-growth forests — contributes significantly to increased temperatures and extreme weather patterns worldwide.

The Threat to Old-Growth Forests

Despite their immense value, old-growth forests are constantly threatened by human activities, including logging, agriculture and urban development. According to the Food and Agriculture Organization (FAO) of the United Nations, the world lost around 10 million hectares of forest annually between 2015 and 2020 — a significant portion of that loss involving old-growth forests.

Logging — in particular — targets old-growth forests because of their large, valuable timber. Although wood is seen as an eco-friendly building material, trees take hundreds of years to mature and regrow. Consequently, using recycled, reclaimed wood from abandoned structures or old homes and buildings is better than destroying old-growth forests or disturbing the ecosystem. In some cases, deforestation leads to desertification — where the land becomes barren and unable to support plant or animal life.

5 Ways You Can Help

While the challenges facing these forests may seem overwhelming, you can take steps to protect these integral ecosystems.

1. Reduce Your Carbon Footprint

Since old-growth forests are vital in carbon sequestration, reducing your carbon footprint helps protect them. You can do this by minimizing your energy consumption, driving less and adopting renewable energy sources — like solar and wind — in your home. 

2. Advocate for Conservation

One of the most impactful things you can do is advocate for old-growth forest conservation. Support organizations dedicated to forest preservation, such as the Rainforest Alliance or Conservation International. These organizations work to protect old-growth forests and restore deforested areas. You can also write to local policymakers and push for legislation protecting old-growth forests from logging and development.

3. Support Sustainable Products

Look for products made from sustainably sourced materials, such as Forest Stewardship Council (FSC)-certified wood and paper. The FSC label ensures products come from responsibly managed forests prioritizing conservation and sustainable use. By choosing these products, you help reduce the demand for timber sourced from old-growth forests.

4. Participate in Reforestation Programs

Reforestation initiatives aim to restore deforested areas by planting native tree species and protecting young forests. While these efforts do not replace old-growth forests, they help create new habitats and restore ecosystems. You can get involved in local or global reforestation programs by donating, volunteering or participating in tree-planting activities. One Tree Planted and Eden Reforestation Projects are two organizations focused on reforestation efforts globally.

5. Educate Others

Spread awareness among your friends, family and community about the importance of old-growth forests. By sharing what you’ve learned, you can help inspire others to take action and join the fight to protect these irreplaceable ecosystems.

Protecting Old-Growth Forests for Future Generations

Old-growth forests are more than just natural wonders — they are critical to the health of our planet. From sequestering carbon to supporting biodiversity and filtering water, these ancient ecosystems provide countless benefits we cannot afford to lose. By making small, sustainable changes in your daily life, supporting conservation efforts and spreading awareness, you can help protect old-growth forests for future generations.