When it comes to fighting climate change with forests, it’s easy to think all trees are equal. This thinking has led to simple approaches that focus on tree numbers rather than the complexity of the forest. However, science tells a different story: old-growth forests and tree plantations store carbon in distinct ways, and this matters significantly for climate action.

Understanding these differences is crucial for making informed decisions about where and how to utilize limited resources for maximum climate impact. While both old-growth forests and plantations help fight climate change, their unique traits mean they serve different purposes in our carbon toolkit.

How ancient forests work as carbon warehouses

Old-growth forests are like sophisticated carbon storage systems that have been built over hundreds of years. Unlike the neat rows of plantations, these ancient ecosystems have multiple layers of trees at different ages, sizes, and species, creating a complex living structure. This diversity is crucial for storing carbon.

The massive tree trunks in old-growth forests represent centuries of carbon buildup. A single large tree can capture as much carbon in one year as an entire medium-sized tree contains in its whole body. In some forests, large trees make up just 6% of all trees but account for 33% of the forest’s yearly growth. This shows why size matters when it comes to carbon storage.

Most importantly, old-growth forests store carbon in many different ways and places. Above ground, carbon is locked in living trees, dead standing trees, and fallen logs that take decades to break down. Below ground, massive root systems and centuries of built-up soil create huge underground carbon vaults. This multi-layered storage system provides both capacity and strength.

How plantations store carbon differently

Tree plantations take a simpler approach to forest carbon storage. Typically composed of a single species planted simultaneously, these managed forests prioritize rapid growth and uniform development. While this works well for timber production, it creates different carbon storage patterns.

Plantations excel at rapid carbon capture during their early years. Young, fast-growing trees can remove carbon at impressive rates—studies show that planted forests can remove between 4.5 and 40.7 tons of CO2 per hectare per year during their first 20 years of growth. This rapid uptake makes plantations valuable for quickly pulling carbon from the atmosphere.

However, plantation carbon storage follows a different path than old-growth systems. The same-aged structure means trees typically reach peak carbon storage at the same time, followed by harvest cycles that release much of the stored carbon back to the atmosphere. While some carbon stays stored in wood products, the forest itself resets to nearly zero carbon storage with each harvest.

The numbers show the difference

The gap between old-growth and plantation carbon storage is huge. Old-growth forests in some regions can store extraordinary amounts of carbon. For example, they store up to 1,300 tons of carbon per hectare in coastal British Columbia forests. Some estimates also suggest that pristine old-growth could have stored up to 2,000 tons per hectare before widespread logging. By comparison, new clearcuts store essentially no carbon in tree trunks, while mature forests typically store around 149 tons of carbon per hectare.

These numbers reflect not just age differences, but the fundamental structural differences between forest types. Research shows that converting old-growth forests to younger managed stands greatly reduces carbon storage, and second-growth forests don’t approach old-growth storage levels for at least 200 years. Even when accounting for carbon stored in wood products, timber harvesting typically results in a net release of CO2 to the atmosphere.

The staying power of carbon storage also differs dramatically. While plantation carbon may be harvested and released within decades, old-growth forest carbon can remain stored for centuries. This time difference is crucial when considering climate goals that need both immediate and long-term carbon storage.

The role of soil 

One of the biggest yet often overlooked differences lies beneath the forest floor. Old-growth forests develop deep, carbon-rich soils over centuries, with organic matter continuously building up from fallen leaves, root decay, and fallen trees. These soils can contain more carbon than all the above-ground trees, creating vast underground carbon reserves.

Research in old-growth forests has found soil carbon buildup that challenges previous assumptions. In one 24-year study of an old-growth forest in China, soil carbon concentration increased from 1.4% to 2.4%, with soil carbon stock increasing at an average rate of 0.61 tons of carbon per hectare per year. This finding suggests that soils in old-growth forests continue to absorb carbon, even in mature ecosystems.

Plantation soils, while potentially carbon-rich if established on former forest land, face different challenges. The simplified ecosystem structure, reduced variety of organic inputs, and management practices can speed up soil carbon loss, potentially limiting long-term soil carbon storage compared to natural forest systems.

What this means for tree planting

For organisations focused on tree planting and forest restoration, these differences suggest a balanced approach to carbon impact. Plantations aren’t bad; they serve essential roles in restoring damaged lands and delivering rapid early carbon capture. However, understanding their limits helps set realistic expectations and improve strategies.

When the goal is maximum carbon storage, protecting existing old-growth forests should matter almost equally, if not more. Research consistently shows that preventing forest loss provides more carbon storage benefits than planting new forests; avoiding deforestation delivers roughly twice the carbon benefits as planting new trees. This doesn’t reduce the value of tree planting, but it puts it in context within a broader climate strategy.

For new planting projects, the approach matters significantly. Native species mixtures that copy natural forest development patterns can eventually develop old-growth traits if given enough time and proper management. These “future old-growth” forests represent a bridge between immediate plantation benefits and long-term carbon storage goals.

Perhaps the most important lesson involves timeframes and managing expectations. While plantations can deliver impressive carbon capture rates in their early decades, old-growth forests provide irreplaceable long-term carbon storage that took centuries to develop. Creating new old-growth forests requires patience measured in multiple human lifetimes.

This time gap between climate urgency and old-growth development highlights why both approaches are necessary. Plantations can contribute to near-term carbon goals while new forests slowly develop toward old-growth status. Meanwhile, protecting existing old-growth forests preserves irreplaceable carbon stores that would take centuries to replace.

The path forward

The science suggests that seeing old-growth versus plantations as an either-or choice misses the point. Effective forest climate strategies need both approaches, used strategically based on landscape context, existing forest conditions, and specific carbon goals.

The most effective approach combines three elements: protecting existing old-growth forests as irreplaceable carbon stores, strategically using plantations for rapid carbon uptake on suitable sites, and managing new forests with long-term carbon storage in mind. This may result in longer harvest cycles, mixed-species plantings, and management practices that foster the development of old-growth characteristics over time.

For tree planting organisations like EcoMatcher, this integrated approach offers a pathway to maximum impact. By protecting what exists, strategically planting where appropriate, and managing for long-term carbon storage, these organisations can contribute to both immediate and century-long climate goals.

The forest carbon story isn’t simply about young versus old, but about understanding how different forest types contribute to climate solutions across different timeframes.

Both old-growth forests and well-managed plantations have roles to play—but only when we understand and respect their fundamental differences can we use them effectively in our collective climate response.