At Wood Lane Nature Reserve we have a constant battle against a non-native invasive water plant. The New Zealand Pygmyweed is, as the name suggests, a waterplant that's normally found in New Zealand or Australia, but was brought into the UK as an ornamental pond plant. By the 1950's it had escaped into the wild, and began to infest waterways around the country.
Battling New Zealand Pygmyweed
Wood Lane Nature Reserve faces an ongoing challenge with New Zealand Pygmyweed, an invasive aquatic plant that forms dense mats and disrupts habitats for wading birds. After spreading aggressively during the COVID pandemic, the weed covered key mudflat feeding areas up to 30 cm deep...
New Zealand Pygmyweed
(c) GB Non Native Invasive Species Secretariat
The problem with the plant is that it grows as a dense mat, smothering out other plants. It's also tough, refusing to die back in our winter climate, and can grow from a tiny piece. This makes it extremely difficult to eradicate, and usually our best hope is to control it the best we can.
Wood Lane is divided into multiple pools, separated by bunds. The bunds allow us to control the water levels, as well as providing habitat for birds that nest on the margins. They also help prevent the spread of the Pygmyweed into the other pools. Lapwing Hide faces out over the largest of the pools, and the majority of the pool is very shallow. This is ideal for wading birds who seek out food in the mud flat. However, unfortunately, this is also the worst affected area by the New Zealand Pygmyweed.
The mud flat is sufficiently wet that the weed can spread across it, and once it's there, it thickens and adds layer after layer. We can usually keep removing it, but during the Covid epidemic work was disrupted, and this enabled the weed to get a much stronger foothold.
This year we found that it had established a mat up to thirty centimeters deep. The entire flat had no exposed mud, and it was impossible for the wading birds to feed there. So, we needed a more drastic approach to removal.
The site is owned by Tudor Griffiths, and is a former quarry site that they have restored to nature. Right next door, the quarry continues to be in operation, and Tudor Griffith have a keen eye on the restoration. It also meant that when it came to clearing the Pygmyweed, they were on-hand to help. One of their quarry workers brought over a long reach excavator, and scraped the surface of the pool, removing the Pygmyweed.
The mixture of mud and Pygmyweed were placed on the side of the pool to allow creatures to escape back to the pool, and then the next day it was removed. The waste was disposed in a land-fill site, which ensured that the removed Pygmyweed couldn't escape to any other watercourses. The excavator was also carefully cleaned to prevent contamination of other areas.
The area is now restored to a mudflat, and the waders can feed again. It was impossible to remove all traces of the Pygmyweed, so it will continue to return and challenge us. However, we're now dealing with smaller areas on the banks of the pool, and we're confident we won't return to the state of a thirty centimeter solid mat again.
John Harding