What Are Primary and Secondary Forests?

Nature-based solutions (NbS), especially forestry, are increasingly recognized for their role in fighting climate change. When developing forestry-based carbon projects, it's important to understand the difference between primary forests and secondary forests.

Primary Forests

Primary forests—also known as old-growth forests—are ecosystems that have never been significantly disturbed by human activity such as logging, agriculture, or mining. These forests maintain ecological integrity and often support indigenous communities who help protect them.

• Carbon Potential: Tropical primary forests store over 141 billion tons of carbon, making them one of the most effective natural carbon sinks.

• Global Coverage: They account for 26% of natural forests, with the largest areas found in Brazil, Canada, and Russia.

• Biodiversity: They host complex ecosystems that are more resilient to climate stress.

These forests develop through a process known as ecological succession, eventually reaching a stable “climax community” dominated by tall hardwoods and diverse species. This makes them essential in achieving global net-zero goals.

Secondary Forests

Secondary forests emerge after a disturbance—such as deforestation, fire, or farming—and undergo regeneration. They usually:

• Contain less biodiversity and lower carbon stock compared to primary forests.

• Have denser undergrowth and sparser canopies.

• Offer potential to recover up to 100% of species richness through natural regeneration, given sufficient time.

Despite their limitations, secondary forests are crucial for restoration-based carbon projects. If properly protected, they can deliver significant ecosystem services including carbon sequestration, soil stabilization, and biodiversity support.

Don’t Forget Planted Forests

In addition to natural forests, there are planted forests established by humans for timber, energy, or conservation purposes. These are fewer in number but may also serve as viable carbon sinks under the right conditions.

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References:

Klorane Botanical Foundation. (n.d.). Primary, secondary, virgin or natural... the different types of forests. Klorane Botanical Foundation. https://www.kloranebotanical.foundation/en/primary-secondary-virgin-or-natural-different-types-forests

Ruiz, S. (2020). What are Primary Forests and Why Should We Protect Them? Global Forest Watch. https://www.globalforestwatch.org/blog/forest-insights/primary-forests-definition-and-protection/

Trimmer, C. (2018). “Second best or second chance?” Why regrown tropical forests are worth protecting. SEI. https://www.sei.org/features/secondary-forest-value/