old growth forests


Old-growth forests are forests that have attained a mature or advanced stage of ecological development. These forests are typically several centuries old and have been undisturbed by human activity. They boast a majestic structure comprised of towering old trees, snags (dead standing wood), branches and fallen logs – all intricately placed to create an impressive landscape abounding with life!  Old-growth forests support high levels of biodiversity and provide critical ecosystem services such as carbon storage, water regulation, and soil stabilization.

old-growth forest structure

Old-growth Forest Structure

The structure of an old-growth forest can vary depending on the specific ecosystem, but there are some general characteristics that are often present:

  • Canopy layer: The canopy is the top layer of the forest and is composed of the tallest and largest trees. These trees often have a complex branching structure and their crowns interlock, forming a continuous cover that can reach heights of 200 feet or more.
  • Understory layer: Below the canopy is the understory layer, which is made up of shorter trees and shrubs that grow in the shade of the canopy. These plants often have unique adaptations that allow them to thrive in low-light conditions.
  • Herbaceous layer: This layer consists of small plants, ferns, and grasses that grow on the forest floor.
  • Snag and downed wood layer: Old-growth forests typically contain a significant amount of dead wood in the form of standing snags and fallen logs. These structures provide habitat for many species of insects, fungi, and other organisms.
  • Root layer: Beneath the soil surface is the root layer, which includes the complex network of roots from the trees and other plants in the forest. These roots play an important role in nutrient cycling and water retention.
old-growth forest function

Old-growth Forest Function

Old-growth forests play a number of important functions within their ecosystems and beyond. Some of the key functions of old-growth forests include:

  • Biodiversity: Old-growth forests are often home to a wide variety of plant and animal species, many of which are unique to these ecosystems. They provide habitat for many endangered and rare species and support the overall health and diversity of the ecosystem. Sunlight can pass through canopies in old-growth forests, all the way to the ground. These forests are home to many different types of plants, and there is a lot of vegetative cover. Old trees also sustain many kinds of animals, including some that are endangered. Dead trees and fallen logs add nutrients to the soil. This encourages soil microbes to grow.
  • Carbon sequestration: Old-growth forests are important carbon sinks, storing significant amounts of carbon in their trees, soil, and other organic matter. Old-growth forests store more CO2 than young forests, so protecting and conserving old-growth forests is therefore an important strategy for mitigating climate change. When old-growth trees are cut down, carbon is released into the air. This can have a very bad effect on the environment.
  • Water regulation: Old-growth forests play a key role in regulating water flows and maintaining water quality. They absorb and retain large amounts of rainfall, reducing the risk of flooding and erosion, and release water gradually over time, helping to maintain steady water flows in streams and rivers.
  • Soil conservation: The complex root systems of old-growth forests help to stabilize soil and prevent erosion. They also contribute to soil fertility by cycling nutrients and organic matter.
  • Cultural and spiritual significance: Old-growth forests have cultural and spiritual significance for many Indigenous communities and other groups around the world. They are often seen as places of spiritual renewal, cultural heritage, and traditional ecological knowledge.
old-growth forests


(Research from Encyclopedia.com)

  • Old-growth forests have unique features that make them different from other forests.
  • Old-growth forests have multi-level canopies that are made up of both live and dead trees, making them very interesting. Also, because of the forest’s pit-and-mound topography, canopies may also grow there, as well.
  • For a forest to be old growth, it must be at least 120 years old. However, some of the trees may be older than the forest itself, which is why we need to be careful.
  • Old-growth forests also have trees with big diameters that are either standing or down. Every single tree in the forest has an important job to play, even if it’s dead.
  • They have both young and old trees in them. The older trees have more stems than the younger ones. Because they are so tall, they cover a lot of ground in a forest.
  • The barks of trees found in old-growth forests are often covered in moss and lichens.
importance of old-growth forests


Old-growth forests play an important role in the world around us. They give animals food, shelter, and a lot of other good things:

  1. Sustains Biodiversity

Old-growth forests add more species to an ecosystem. These forests are home to both plant and animal species.

The canopies in old-growth forests let sunlight reach the ground. There are a lot of different plants in the forests, so there is a lot of vegetative covers.

Old trees also have a lot of different kinds of animals, including some that are in danger.

The dead trees and fallen logs add nutrients to the soil. This lets soil microbes grow.

  1. Supports Ecosystem Functions

In terms of ecosystem services, these forests are very important because they do a lot for the whole world.

They help plants and animals live together in an ecosystem by giving them food and shelter.

In addition, they use the hydrologic cycle to filter water.

The trees also clean the air, which means that animals can breathe.

  1. Carbon Storage


Older trees take in a lot of carbon from the air each year. This makes old-growth forests a good place to store carbon for the Earth.

There is even more carbon dioxide in the air as the forest grows old.

When old-growth trees are cut down, carbon is released into the air. This can have a very bad effect on the environment.


The United States has about 8% of the world’s forest
cover. The largest area of old-growth forest in the
United States is found in the state of Alaska.


  • Many types of old-growth forest can be found in Oregon. The area used to be covered in old trees, but their numbers have since dropped. Around the Clackamas River, you can find some of the oldest old-growth forests in the world. 
  • The largest old-growth forests in Oregon are the Winema National Forest, at about 712,000 acres, and the Willamette National Forest, at 1,675,407 acres.
  • Most forests in Oregon are overseen by the federal government. This helps protect the old-growth forests in the area.


  • Michigan only has a few old-growth forests. Many old trees in the state were cut down in the 1800s.
  • There are a lot of trees that are old enough to be called “old-growth” in Northern Michigan and the Upper Peninsula. The forests in this area are mostly made up of pine trees and trees that are still standing.
  • If you go to Hartwick Pines State Park, you can see some of the oldest trees in Michigan.


  • There aren’t a lot of old-growth forests, but all of the old-growth forests that are still there are protected.
  • If you live in Washington, you should visit the Mount Baker-Snoqualmie National Forest. It is one of the largest old-growth forests there. It’s about 644,000 acres.


  • Pennsylvania has up to twenty places where old-growth forests still stand. Most of the trees were cut down in the late 1800s, but the government has been able to save some areas.
  • Cook Forest has been around for a very long time. Most of the trees are around 300 years old. This area is mostly made up of pines and hemlocks that grow tall.


The world’s old forests are under threat. Areas that used to be covered by old trees have been left empty by people who do things that hurt them. Old forests are not only beautiful, but they also have a lot of sentimental value to the people who lived there before.

But the most important thing is that old-growth forests are carbon sinks. They play an important role in reducing the amount of carbon dioxide in the air around the world.

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