Nature on our doorsteps: Holding back the water

Rosaleen Dwyer is the County Heritage Officer at South Dublin County Council – every week she gives us an insight into the natural heritage around us and the beautiful biodiversity of the plants and creatures.

HIGH up in the Dublin Mountains, the landscape is covered with a layer of wet bog.

This peaty habitat is known as blanket bog, because it literally covers the slopes of the mountain like a blanket.

In flat areas, swampy hollows are filled with wet mosses and open pools.

Drier mossy hummocks occur on sloping ground, allowing bushes of heather, grasses, and dainty flowering plants to grow away.

While blanket bog provides a specialised home for a range of uncommon plants, insects and birds, it also does another very important job.

It acts like a giant sponge, holding onto rainwater in its mossy, peaty, soils and in its open pools.

Partly blocking drains in the hillside slows down the water coming off the mountains

Over a period of time water drains away very slowly from the bog into little streams that trickle down the mountain to form rivers like the Dodder River.

In this slow process, water does not rush quickly down to the urban areas of Dublin where flooding might occur.

This only works, however, if the bog is not damaged.

Over the centuries, drains were dug into the mountain bogs to dry out the peat so that it could harvested as turf to heat homes.

Today, while turf is no longer harvested in the Dublin Mountains, the drains that were dug a long time ago continue to draw water from the bog.

As peat dries out, it no longer holds water like a sponge.

Also, the dried-out bog begins to decompose, releasing bound-up carbon back into the atmosphere where it adds to the challenge of climate change.

The National Parks and Wildlife Service are currently blocking drains in the mountains to help slow down the water coming off the mountain.

They are also using unusual-looking long rolls of coir and hemp fibre which are placed in sloping areas to help hold water on the bog surface.

This restoration project will hopefully help the mosses grow once again and form healthy bog habitat.

This nature-based solution will help us manage the water coming down from the mountains, while also helping to reduce carbon escaping into the atmosphere.