Works in the Wetlands

Woodland Ranger, Richard Cornock, talks us through the maintenance tasks that have been conducted at Cardiff Bay Wetlands Reserve recently.

The work to clear the reen takes place every 10 or so years. The purpose is to open up the waterway, clear the accumulated debris and control the woody growth, such as willow and bramble. The reen acts as a reservoir for the numerous ponds on the reserve and the two large reed beds. This reen accounts for 5% of the reed cover, and 80% of the reen has been cleared, leaving 20% as a refuge whilst the works take place.

Over the years, we have lost the variation of marginal plants along the water edge, especially plants like purple loosestrife. The reed will soon recover, and certainly by the time our migrant birds return to nest, a more diverse water edge will have been created. The reserve holds more than enough reserve habitat to accommodate this amount of work.

The pond has had some major work carried out near one of the outflows because it was leaking. Following concerns from Natural Resources Wales about the extent of the reed cover, it was decided to repair the outflow and try and get the water level back to its desired height, some 300mm higher that it is currently.

The phragmites on the northern edge was drawn back to clear several years of growth which had turned into a dry raft and started to become invasive into the main pool. This work will now encourage new growth and create a better habitat for birds like sedge warbler. Only 20% of the reed has been removed. It is hoped when the water level rises, it will help control the algae which had taken hold in the shallower, warmer water.

I find it easier to manage and it is certainly less destructive to do the work all in one hit rather than stagger it over a few years – the site will now be fit for our many breeding birds for the next 10 years. This work, apart from some annual coppice works, will not need doing for another several years.

We have been carrying out targeted coppice works on the reserve itself to prevent the reed beds transitioning to woodland. Whilst I had the machines on site, I have taken the opportunity to create some open water within the reedbeds in the main reserve. This is no more than 5% of the total reed bed cover per plot.

We used thermal imaging binoculars to survey the site prior to and during the works, and chose the best time of year to undertake them using a specialist environmental contractor and our own inhouse staff. The works will help the reserve to develop into a more diverse habitat.