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How to create a thriving forest, not box-checking 'tree cover'

A Chinese proverb says that the best time to plant a tree was 20 years ago, and the second best time is today. But it's not easy to ensure the trees of today actually become the healthy, functioning forests of tomorrow.

This is a key issue in the UK, which recently announced it will plant 20 million trees to create a in the west of England. Given the UK is one of the least forested countries in Europe, and one of the most in the world, more trees are definitely needed.

But I know from years of trying to in the south west of England, that creating healthy forests requires attention to detail. Unless we are careful, these new woodlands might damage rather than improve the environment: 20 million non-native conifers (or any single tree species), densely planted row on row is not a recipe for a healthy or resilient forest.

So what could a successful forest expansion look like—and how could the UK get there?

Forests for the future

When planting a sapling, we are starting a journey, not reaching a destination. The aim isn't to just grow dense forests everywhere, but to create a diverse "treescape" that includes woodland, pasture, orchards and hedgerows. Including glades and clearings allow plants and animals from the surrounding landscape to move in, helping to create a richer, more complex forest over time.

In this ideal future, Britain's bigger, more diverse, and better joined-up forests would have a higher chance of coping with the hotter summers, wetter winters and including extreme weather. That's because these larger more connected forests limit what is known as the "" where the benefits of the forest's microclimate is reduced. Having more different tree species—mostly native but not always—would help these woodlands cope with, and adapt to, the projected increase in pests, disease and other environmental stresses.

These larger more biodiverse woodlands would also store more carbon in trees, soils and decaying wood. I published with colleagues showed new native forests can alleviate flood risk rather quickly too. Over time, many could also for low-carbon construction, and charcoal-like "."

Where to grow a forest—and how

Creating woodland for biodiversity and these wider benefits requires . This can be done by studying the land beforehand—looking at habitats, soils and the animals that graze there, but importantly considering the wider landscape. Digital tools can model a combination of land features, climate and other data to help planners decide where trees should be targeted for the biggest wins, especially as the climate changes.

The idea is to support, not replace, Britain's many . Some new forests would help buffer woodlands from damage at their edges, while others help connect isolated forest fragments and lone trees.

For example, in Britain's wet valleys where , saplings planted in the 2020s might provide new homes for . This will help shield highly vulnerable sites such as Wistmans Wood on Dartmoor from changes in climate.

Restoring these rainforests will usually require . One promising solution is to plant small, carefully chosen patches of diverse tree species and protect them at first from the sheep, cattle, ponies and deer that eat young trees. Over time, through a process known as "," these patches could help trees naturally spread, creating a mix of woodland and pasture.

It's true that sapling-munching deer have , and many uplands areas in particular are overgrazed by sheep. However, when moderated and managed carefully, these animals are essential ingredients for dynamic forests. Grazing, browsing and rootling (pigs and wild boar) animals create glades and clearings, and support natural processes. Trees and forests in return provide animals with forage, shade, shelter and more.

We should embrace the potential for mutual benefit between animals and forests. By integrating more trees and forests into agricultural areas we may even make both our forests more dynamic and our agricultural areas more resilient.

Local leadership and community roots

The public generally considers tree planting a positive thing, but local people often feel left out of the process and its benefits. Getting them onboard and involved is critical. That's particularly the case in Britain's northern and western uplands, where few trees are left and many people feel threatened by national woodland policies that might affect how they use the land.

Moor Trees on Dartmoor, or and in 15 regions of England show there are ways to get locals involved and empowered.

Larger forests near towns and cities would offer more space for recreation and education, taking pressure off smaller and more fragile woodlands. In the urban areas themselves, we could grow more . These are tennis court-sized areas of diverse and densely packed native trees, which allow children to connect with nature every day in their school grounds (the UK already has such forests).

Tree planting is only a start

This is a rather optimistic vision for the future, of course. To get there, we'll have to learn from experience. That means tracking what works and involving local people in citizen science. These projects not only help gather valuable data, they also give volunteers a meaningful experience and support their appreciation of the natural world.

There are plenty of recommended guidelines for forest restoration, but turning young trees into healthy, resilient woodlands isn't about following a strict rulebook. Instead, success will come from using a range of strategies—working with local communities, supporting natural processes and adapting over time based on what is shown to work.