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Ambitious government plans to expand Britain’s woodlands as part of efforts to combat climate change, could have mixed consequences for the country’s wildlife, new research from the University of Sussex has found.

While the UK Government’s 2023 Net Zero Growth Plan - which aims to increase England’s woodland cover to 16.5% by 2050 - could deliver major conservation benefits for many native mammals, it may also put species that rely on open grasslands at risk, according to a study published in Mammal Review.

The study – the first to model the nationwide effects of woodland creation on British wildlife – predicts that if targets for 2050 are met, most mammals - including rodents and deer - will see their populations rise by around 7%, with some woodland specialists such as pine martens and red squirrels gaining as much as 30% more suitable habitat.

However, the models also reveal that grassland-dependent species like mountain hares and brown hares could lose up to 9% of their remaining suitable habitat, highlighting the need for careful planning to avoid unintended losses.

“Britain is one of the most woodland-depleted countries in Europe. Reversing that trend is important to tackle climate change, but we need to make sure it also benefits wildlife,” said Professor Fiona Mathews. “Our study shows that while woodland creation offers clear opportunities for many species, the wrong trees in the wrong place could be damaging for others.”

“Importantly, our predictions assume that new woodland will largely be made up of a diverse mix of native broadleaf trees - what we need to avoid is planting dense stands of non-native conifers, which may contribute towards climate goals but provide very little benefit for wildlife,” said lead author, Dr Bronwen Hunter.

A national picture for nature recovery

To help inform the study, the team simulated the conversion of suitable areas to woodland across England, Scotland, and Wales using the most recently published policy targets, as well as recorded rates of woodland expansion in recent years. And based on knowledge of those areas’ ranges and population density, the team then assessed how this would affect habitat availability and population size for 27 species (excluding bats) from 2023 to 2050.

Through their simulations, the team predicted that 12 of the 27 assessed mammal species (44%) would gain at least 5% of suitable habitat area within their ranges (across England, Scotland, and Wales) between 2023 and 2050, if current woodland creation targets were achieved but four species (European hare, mountain hare, European badger and pygmy shrew) were predicted to lose suitable habitat from woodland creation.

The team concluded that current policies driving the expansion of tree planting across the UK represent a key opportunity to improve the conservation status of woodland-dwelling mammals. However, responses are species-specific, with grassland-dependent species predicted to lose suitable habitat if woodland creation is distributed randomly according to the availability of suitable sites. This is particularly concerning, as some grassland-dependent species, such as the mountain hare, are already threatened with extinction. The team recommends smarter, balanced planting — combining woodland expansion with protection of open habitats — to maximise benefits for biodiversity.

“Woodland expansion can be a win-win for climate and biodiversity — but only if we plan carefully for species that thrive outside forests too,” said Dr. Bronwen Hunter.

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