Primary Forest Overview


Earth’s spectacular primary forests are unique and irreplaceable ecosystems, unmatched in their ability to provide ecosystem services as nature-based solutions. They are very often the homelands of Indigenous Peoples, essential to Indigenous cultures and local livelihoods. Primary forests include over two thirds of the planet’s land and freshwater species, and countless endangered species, they fight climate change by storing vast amounts of carbon and drawing down carbon from the atmosphere, ensure reliable, high quality drinking water, and may also function as natural quarantine areas by limiting the spread of zoonotic diseases like COVID19. Primary forests are therefore essential life-support systems, critical to addressing many of our most urgent environmental and social problems.

But they are going fast. We’ve already lost over a third of Earth’s forests, less than a third of our remaining forests are primary, and we lose millions of hectares of primary forest each year. We urgently need to protect our remaining primary forests, large or small! Even small patches are important: they are critical building blocks because they provide the seed banks and seed dispersers (birds, pigs, monkeys etc.) we need to bring forests back.  

Primary forests and large, old trees provide unmatched biodiversity, clean water, and carbon benefits (our Chief Scientist, Dr. Dominick DellaSala and Dr. William Moomaw summarize their values.

 See also this key paper defining primary forests.

Giant sequoia in the Sierra National Forest
Photo: D. DellaSala)

Primary Forest Frequently Asked Questions

What is a primary forest?

A primary forest is a forest that is the result of natural processes rather than human management, and that has not been degraded by industrial activities. Mature trees often dominate the forest canopy and a primary forest contains most or all of its native plant and animal species. Primary forests include all successional age classes (young to old-growth), including primary forests regenerating after wildfire and other natural disturbances.

More specifically, a primary forest is a forest whose vegetation structure, species composition and ecosystem dynamics are predominantly the product of natural physical, ecological and evolutionary processes, including natural disturbance regimes such as fires, storms, floods, insects, and landslides. Primary forests retain most if not all of their evolved, characteristic native plant, animal and microbial species, have few if any invasive species, are often dominated at the landscape scale by mature canopy trees, contain many large dead standing (snags) and down (logs) trees, and have not been subject to industrial land use activities such as commercial logging, mining or ranching.

As a “chapeau” term, primary forest covers a range of related terms including “old-growth forest”, “ancient forest,” “primeval forest,” and “intact forest landscapes.”

Why are primary forests important?

Primary forests ensure a wide range of vital ecosystem services that are either unique, or are of a superior quality and quantity to degraded forests, secondary re-growth forests, or plantations. In particular, they:

  • Protect the most biodiversity (plant, animal and invertebrate species) – at least two thirds of the planet’s terrestrial and freshwater species are found in primary forests;
  • Store 35-70% more carbon than degraded forests or plantations and their carbon stocks are more stable because primary forests are more resistant to change, and more resilient when natural change inevitably happens. To avoid dangerous climate change, we must protect the massive carbon stocks already accumulated in primary forests.
  • Provide the cleanest freshwater, prevent erosion and help regulate local water cycles.
  • May prevent the spread of zoonotic disease to humans. Deforestation and degradation of primary forests and associated road building (e.g. logging or mining roads) often enables bushmeat trade and wildlife trafficking and facilitates disease transmission to humans.
  • Many are homelands of Indigenous Peoples that are crucial for sustaining traditional cultures and community livelihoods. Primary forests often remain in good condition because of Indigenous and community stewardship.

Importantly, primary forests provide more and higher quality ecosystem services because of their higher levels of biodiversity and ecosystem integrity. To protect a primary forest’s ability to provide its full range of benefits it is critical to protect it from inappropriate land use activities, including industrial disturbance.

How much primary forest is left?

The world already has lost over a third (about 35%) of the planet’s pre-agricultural primary forests. Just over a quarter (27% or 1.1 billion ha) of the world’s forests remain in a primary forest condition. 

Source: Mackey et al. 2014. Policy Options for the World’s Primary Forests in Multilateral Environmental Agreements. Conservation Letters

How much primary forest are we losing?

According to the UN’s Food and Agriculture Organization we are losing about 4 million hectares per year, though FAO statistics on primary forests significantly underestimate loss because the government reports they are based on are not always reliable and some governments do not report on primary forest loss at all. The recent scientific literature suggests that forests are being fragmented and degraded at very high rates. For example, a study in 2015 found that 70% of the world’s forests were now within one kilometer of a forest edge (road, clearing, pipeline etc.). A 2017 study found that large, contiguous blocks of forest (50,000 hectares or more) had decreased by over 7% since the year 2000.

Why are we losing primary forests?

Industrial agriculture is a primary driver of deforestation globally, including of primary forests. Primary forests are being cleared to make room for crops such as palm oil, soy etc. and for cattle ranching. Oil and gas extraction and mining also contribute to deforestation, as do large-scale infrastructure such as roads and hydropower projects.

Primary forests are also being degraded primarily by commercial logging and by fuelwood gathering. Despite decades of efforts to develop best-practices for the logging industry, commercial logging has not proven sustainable in primary forests and often leads to total deforestation as degraded forests whose valuable timber has been removed are converted to agriculture.

In many regions, growing human populations are expanding the footprint of slash and burn agriculture. Helping communities farm more sustainably and develop alternative development pathways based on forest conservation is a prerequisite for protecting the world’s remaining primary forests.

What can we do to stop primary forest loss?

We know the range of mechanisms that are effective at protecting primary forests. Protected areas with good governance and adequate funding can successfully protect primary forests. Similarly, community conservation initiatives and Indigenous peoples have a proven track record of protecting primary forests – often over millennia. Payments for ecosystem services schemes have also met with success. Conversely, it is crucial to stop viewing commercial logging as a sustainable and viable solution for protecting primary forests. Commercial logging has not proven sustainable in primary forests anywhere.

We need to “flip” incentive structures so that national and multilateral subsidies are directed to mechanisms that have demonstrated capacity to achieve primary forest protection – and to restoring degraded forest or regenerating forest. Currently, subsidies for industrial agriculture, extractive industries and other industrial developments far outweigh conservation funding. Shifting this balance to support actors on the ground that have a commitment and vested interest in keeping primary forests standing – especially indigenous and local communities – can have a profound and rapid effect on primary forest protection globally.

Help restore degraded lands and manage wildland fires safely!