Student Project: ‘Death, Dunes and Pretty Pink Flowers: The problems posed by Japanese Rose on dune biodiversity’
Hi, I’m Thom Lyons, a Zoology BSc student at Swansea University and I love nature, from ecology to evolution to bird spotting. Over the coronavirus pandemic I missed out on fieldwork opportunities so decided to have a look for something. Through this I found an amazing opportunity to do some funded work for Dynamic Dunescapes at Crymlyn Burrows. This has involved a lot of field work and has given me great experience in the world of conservation ecology research, in which I now wish to pursue a career in. In addition, I also presented my work at the project conference, my first experience of anything of this kind, and talk to the many inspiring people protecting our beautiful dunes.
My Study: The problems posed by Japanese Rose on dune biodiversity
Japanese Rose (Rosa rugosa) naturally grows in east Asia. It was brought to the UK around 200 years ago for its beautiful bloom and its suitability for coastal gardens. Being dispersed by birds, which eat its fruit, it spreads quickly along coastlines, where it has no natural herbivores to control it. Due to this it can take over a dune system, creating a scrubby canopy that blocks the sun for smaller native plants and causing soil to build up, replacing the sand that is so vital to native dune dwellers.
This rose can be removed by digging and burying, exposing sand, so cleared sites become ideal for dune specialist species. At these sites, however, the rose will continue to come up through the ground, and begin to recolonise the site. I wanted to find out how the rose affects the plant and invertebrate diversity, and so support ongoing management.
From June to August, Crymlyn Burrows hums with sound of insects and thousands of flowering plants sway in the wind. This was when I chose to survey, with the greatest diversity, as well as the mating colours or flowers making things easier to identify. To see if Japanese rose covering the sand was damaging the ecosystem, I needed to find cleared sites that had different amounts of rose growing on it. In addition to this I looked at a site that was covered in rose completely and a site that rose had never been found at, to compare to the cleared areas.
At these sites, I used a quadrat to work out how much of the area was covered by each plant species and pitfall traps (a cup buried in the ground to make a pit) to catch some creepy crawlies and see how many lived there. I also used a net to sweep over taller vegetation, so as to look at what was living on the plants. This included over 2300 hours of combined pitfall trapping and hundreds of species to identify. I then compared the diversity to the area covered by Japanese rose to see if more rose meant less of everything else.
And here’s what I found out…
The Diversity Index (a way of measuring biodiversity) plotted against the amount of the area covered by Japanese rose.
As shown above, each group that I studied is less diverse in areas with more rose coverage. Interestingly, the most affected group was the terrestrial invertebrates. This surprised me as the rose is known for outcompeting native plants. The plant diversity also seemed to decrease at a similar rate to the critters living on it. This may be because as the rose outcompetes the native plants, the tiny animals that have adapted to live on and around them will not live on the rose. For example, many moths require specific plants to lay eggs. This in turn affects animals higher up the food chain, such as harvestmen and spiders, which are amazingly abundant at Crymlyn.
Interestingly, despite rose-dominated areas being less diverse, the communities were actually less dominated by single species. This is because dunes are naturally harsh, and so is dominated by specialist species such as marram grass. The rose changes the ecosystem to favour more generalist species. By this we lose the rare specialists to be replaced with animals and plants that are found in a greater variety of habitats.
The amazing biodiversity of Crymlyn Burrows; some of Thom's favourite fieldwork photos
Eyebright (Euphrasia sp.)
Eyebrights are tiny, plants that only grow a few centimetres tall. Due to this they cannot survive under the canopy formed by Japanese rose. They can often be seen growing alongside paths.
Common Broomrape (Orobranche minor)
These funky flowers rely on nutrients from the roots of grasses and hawkweeds which they use to produce the amazing flower tower in the picture above. If the plants that broomrapes feed on disappear then the broomrapes will too, and won’t support pollinators like bees.
A Predatory Mite (Erythreum phalangoides)
This mite parasitises harvestmen which are extremely common at Crymlyn. Once it’s fully grown it become a free roaming predator. This is the first time this species has been recorded in Wales and in my surveys was only found in undisturbed, rose-free dune.
6-spot Burnet Moths feeding on a Sea Holly (Zygaena filipendulae on Eryngium maritimum)
These pretty moths rely on native plants for food such as sea holly, a plant that favours open sand.