A charity has said an increase in the number of ponies in a part of Dartmoor will help restore the environment.

The Dartmoor Pony Heritage Trust said it had been given permission from Natural England to increase the herd of ponies at its site at Bellever from 25 to up to 40 in the summer.

It said it would be allowed to keep a smaller stock of 30 ponies at the 82-hectare (202-acre) site in the winter.

The trust cited a University of Plymouth study, external that found grazing ponies at Bellever reduced the dominance of purple moor grass and its impact on plant and animal diversity.

Healthier seedlings were able to germinate after the ponies trampled the purple moor grass, according to the study.

Malcolm Snelgrove, the charity’s chairman, said the findings were encouraging.

“The positive impact ponies have made at Bellever is very exciting and should help ensure that suitably hardy ponies of all types and breeds are recognised and appreciated as effective conservation grazers to support biodiversity and tackle some of the factors affecting Dartmoor’s landscape,” he said.

The increase to the pony herd at Bellever comes amid a review on the way protected sites on Dartmoor are managed.

It will make recommendations on the “most effective grazing and management regime”, while balancing “long-term and sustainable delivery of other priorities such as agricultural production, public access and cultural and natural heritage”, the government said.