Old-growth forests are at risk. Here’s why they matter so much for people and the planet

The world’s oldest forests are facing growing pressure from all sides. Their decline isn’t just an environmental concern – it carries serious consequences for people, climate stability and global biodiversity.

According to a new World Resources Institute (WRI) report, the world lost more primary rainforest in 2024 than in any other year in at least the last two decades. The WRI defines primary forest as “old-growth forests that are typically high in carbon stock and rich in biodiversity”.

So what makes forests so important – ancient ones in particular – and how are human activities driving their rapid decline?

Old forests are vital to life on Earth.

Whether as carbon sinks or as irreplaceable habitats, ancient trees provide widespread benefits. A 2022 review published in PubMed Central highlighted just how vital they are across ecosystems worldwide. While their role in storing carbon and supporting biodiversity may be well known, did you know they also help regulate below-ground conditions critical for forest regeneration? Or that they have a higher carbon density – storing more carbon within the same footprint – than younger forests?

Whether a tree is ancient or not depends on the species, according to the UK’s Woodland Trust. Take the birch, for example: it grows quickly and might be considered ancient at 150 years old, whereas a yew might take 800 years to reach a similar stage (there’s one yew tree, just outside London, that’s thought to be 2,500 years old). Indeed, the world’s oldest tree, in eastern California, is thought to be the world’s oldest living thing at more than 4,850 years old – older than the pyramids at Giza.

Whether hundreds or thousands of years old, the role of ancient trees and woodland worldwide is clear. As the UK’s Forestry Commission explains: “They are teeming with wildlife – rich irreplaceable communities of often rare species that have developed over centuries and found their last refuge here.” This is true of similar ecosystems in the Amazon, Congo Basin and Southeast Asia, the WRI report notes.

The loss of primary forest can also have an impact on local temperatures and rainfall that can compound the local effects of climate change.

But, as the PubMed review stresses, the benefits of ancient trees and woodlands extend far beyond the planet. They’re also “part of our combined cultural heritage, providing people with aesthetic, symbolic, religious, and historical cues”. Equally, consider the therapeutic benefits of forest bathing, the Japanese practice of shinrin yoku, for our mental and physical health.

Add to that the fact that some 1.6 billion people are thought to rely on forest resources for their livelihoods and the consequences of the loss of ancient woodland become clear.

Human activity has dramatically reduced ancient forests worldwide. Take the UK, for example, which was at one time thought to be 75% covered by wildwood. Today, that figure is just 10%, with only a quarter of that being ancient woodland.

According to the WRI report, 6.7 million hectares of primary rainforest were lost in 2024 alone, largely due to massive wildfires. Globally, an area equivalent to England and Wales is lost to deforestation each year.

Climate change is accelerating the loss of ancient forests. Rising temperatures threaten woodlands worldwide, from the Amazon to the boreal forests of Canada and Russia. A recent University of Leeds study warns that up to 90% of temperate rainforests in some areas could disappear by 2100 – even with immediate emissions cuts, at least 9% may still vanish. As these vital carbon sinks degrade, they release stored carbon into the atmosphere, intensifying global warming and creating a dangerous feedback loop.

How can we break this cycle? It starts with tackling the problem at both ends: preventing deforestation and reducing greenhouse gas emissions. A 2023 study found that protected areas are effective, but focusing on regions most at risk of deforestation – such as agricultural frontiers in the Amazon and Indonesia – is crucial. Financial incentives for conservation and sustainable land use are also highly effective.

Where forests have already been cleared, reforestation plays a critical role. That’s where initiatives like 1t.org, launched by the World Economic Forum, step in. The ambitious goal: conserve, restore and grow one trillion trees by 2030.

The initiative unites public and private sectors, and collaborates with UpLink – the Forum’s platform for early-stage innovation – to drive forward-thinking solutions and support the next generation of environmental entrepreneurs.