If left untreated, bracken would colonise swathes of the dune system at Murlough on the County Down coast.
Dune heath is a key habitat, and 16% of the UK total is in the 700-acre site between Dundrum and Newcastle.
It is home to a range of plant and animal life and a huge variety of moths and butterflies.
There are 700 types of moth and 23 types of butterfly found at Murlough.
The bracken is being removed partly to help them and to manage the habitat.
"Bracken can become invasive," said Patrick Lynch, a conservation ranger at the site.
"It can become quite dense, the fronds get quite high and then nothing can grow underneath it."
The bracken is beaten down so that heathers and other plants that attract moths and butterflies can grow.
Almost 30 acres of bracken is removed each year by the National Trust, which manages Murlough.
They use a combination of rolling and spraying for the task.
The site is also managed by using livestock.
Cattle and 10 Exmoor ponies are allowed to graze in the area to help to keep the bracken down and let other plants flourish.
The bracken is favoured by some butterflies, but it needs to be kept in check.
Conservation workers hope the bracken-clearing initiative will provide a "mosaic of habitats" and balance the interests of all the animals and insects on the reserve.
It is a plant that is really good at growing, and one of our most important nature reserves has more than enough of it.