Biosphere Daily Earth Science Environment Repost

Tongass National Forest: The good, the better, and the beautiful

In the southern reaches of Alaska, nestled between the Pacific Ocean and Canada, lies the Tongass, America’s largest national forest. The Tongass National Forest is also the largest remaining temperate rain forest in the world. The coastal forest and wetlands of the Tongass form a unique ecosystem that sequesters large volumes of carbon. Accordingly, about eight percent of all the carbon stored in U.S. forests is in the Tongass. However, threats to the Tongass are more than just threats to the trees. Changes in land use put pressure on both terrestrial and aquatic ecosystems.  

From a southern border between Ketchikan, Alaska and Prince Rupert, Canada, the Tongass forests stretch some 350 miles northwest along the Pacific coast, encompassing about 17 million acres. This national forest is named after indigenous people in the area.  The Tongass National Forest has its’s origins in a 1902 proclamation by President Theodore Roosevelt, declaring this coastal Alaskan area as the Alexander Archipelago Forest Reserve. Then, five years later, another proclamation created the Tongass National Forest. But in 1909 the two were combined to form the Tongass we know today.

Logging runs amuck

Mountains dive into the ocean along this portion of the Alaskan coast, and some 15,000 miles of rivers and streams in the Tongass drain into the Pacific Ocean. Here, the primary species of trees in the Tongass are Sitka spruce, western hemlock, western red cedar, and Alaska cedar. These trees are commercially valuable. 

Small scale logging occurred before 1950, but in 1954 a large pulp mill operation started in Ketchikan. The contract with the US Forest service supplied 50 years of timber. Then more mills opened, and the pace of logging grew until it was unsustainable. When the ongoing damage was recognized in the 1990s, contracts were canceled, and mills closed. However, by that time, about 90% of the large old-growth forests had been lost.

However, despite the ruinous effect of past logging, efforts are currently underway by policymakers in Washington, D.C., to resume logging in the Tongass.

Tongass carbon stores

The Tongass National Forest plays a significant role in managing greenhouse gas emissions because climatic and environmental conditions are optimal for massive carbon storage. The good news is that the vegetation biomass is huge. However, the better news is that the soils are even more effective at carbon storage. In the Tongass forests, 66 percent of the total carbon resides in the soil, and the remaining 34% is in the vegetation biomass. Also, carbon storage is higher in the Tongass than in most forests.

Contributing factors to the high carbon storage capacity of this ecosystem are a cold climate and high rainfall. Ample water stimulates high growth rates, and colder temperatures retard the rate of decomposition, so more carbon remains locked up. An added benefit of the wet and the cold is reduced susceptibility to wildfires. On average, in U.S forests, wildfires release an equivalent of 25% of the carbon stored annually in trees. So less wildfire translates into better carbon management.

But the real ecological beauty of the Tongass National Forest is its intimate relationship with the aquatic and marine ecosystems along the coast.

Terrestrial and aquatic symbiosis

Some places in the Tongass receive up to 200 inches of rain each year. The constant flushing of water from the steep slopes of the Tongass forests into the ocean connects the terrestrial and aquatic/marine ecosystems of the region. So the nutrients delivered by this system create an aquatic food web that supports Alaska’s multi-billion-dollar fishing industry. 

One of the key foundations for this web of life is the flux of dissolved organic carbon (DOC) from the Tongass soils into the ocean. The streams of the Tongass discharge 36 times more DOC per unit area as the world average and 3 times as much as the Amazon River. Remember, the Amazon drains the largest tropical rainforest in the world. This bit of magic depends on the short travel distance from the rich carbon reserves in the forest soils to the ocean. This distance is significant because long river trips provide more chances for carbon interception before it reaches the sea.

At the base of the food web, micro-organisms consume carbon, thus creating the bottom trophic level of a valuable and complex marine ecosystem. The source of this carbon is the soils, so as commercial logging removes trees, it also changes the soil structure and composition. These changes cascade through life-energy pathways between the land and the ocean. Therefore, understanding complete carbon pathways in the combined terrestrial-aquatic ecosystem of the Tongass is the only way to know how newly proposed logging will affect life along the southeast Alaskan Coast. It’s about more than just the trees.


Extractive versus sustainable logging (Source: ArcheanWeb) – Also:

Forests as a pathway for terrestrial carbon sequestration (Source: ArcheanWeb) – Also:

When do forests become a carbon liability? (Source: ArcheanWeb) – Also:


Tongass National Forest (USDA – Forest Service) – Also:

11 facts about North America’s temperate rainforests (By JAYMI HEIMBUCH; Mother Nature Network) – Also:

Greenhouse Gas Emissions Versus Forest Sequestration in Temperate Rain Forests— A Synthesis for Southeast Alaska Communities (By David Nicholls and Trista Patterson; USDA) – Also:

From rock to forest: Southeast’s carbon sink (By  MARY CATHARINE MARTIN; Juneau Empire) – Also:

Baseline Estimates of Carbon Stocks in Forests and Harvested Wood Products for National Forest System Units – Alaska Region (USDA Forest Service) – Also:


Alaska Forest Facts – Also:

History of the Tongass National Forest (American Salmon Forests)  – Also:

Feature Image: Tongass Rain forest 08 (By Gillfoto) (Modified) – – This file is licensed under the Creative Commons Attribution-Share Alike 4.0 International license. – Also:

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.