Autumn at Sweet Briar Marshes

Autumn at Sweet Briar Marshes

Sweet Briar marshes (credit: Richard Osbourne)

Conservation updates from our Urban Nature Reserves Assistant, Sarah Wilde, this autumn at Sweet Briar Marshes.

Sweet Briar Marshes is a time capsule on the Norwich map. The surrounding landscape has been built up, while the reserve itself has been largely untouched by brick and mortar. The site has a mixed history of being used for both pasture and arable farming, which has led to an impressive assortment of habitats that will be managed for wildlife and people going forward.

This autumn our fantastic volunteer groups have been dredging out various patches of ditch across the reserve. We do this using long bent pitch forks called 'chromes' to scrape away the mud along the bottom of the ditch. This scraping increases the depth in that spot and cuts back the tall growing vegetation, such as sedge, reed, reed sweet grass, and willow herb. 

An aerial image of Sweet Briar Marshes with lots of trees and shrubs.

Aerial image of Sweet Briar Marshes

By making small patches of open water, we are aiding species that lay their eggs in water, such as dragonflies, mayflies, and caddisflies. Deepening and widening the body of water also improves the quality of the habitat, helping species that like to dive and swim such as frogs, toads, newts and diving beetles. The increased sunlight also allows smaller, more light dependent species such as water mint and fleabane, to have their time in the sun and flourish, before the taller vegetation encroaches again.

We can see firsthand the benefit this has for wildlife. Our public work party volunteers hadn’t even put down their tools before common darter dragonflies and mosquitoes started checking out the new source of open water for somewhere to lay their eggs.

We’ve had multiple groups take part in this activity, including our Wilder Wardens’ group of 11-17-year olds, that volunteer with us at Sweet Briar. Chroming is potentially the most gruelling activity we’ve had them try, but as always, they took it in their stride. As they were digging, frogs were swimming around in the newly established puddles along with some little diving beetles. Every new wildlife encounter sparks curiosity and prompts questions from the group and some questions are better than others, often leaving us to Google the answers to learn for ourselves!

One species that is worth mentioning purely for their clear success this year, is the common frog. Most people see a frog a few times a year at best. Over the course of this summer, I have had the very blessed experience of seeing potentially a dozen frogs on any given day.

Years of abnormal weather are doing peculiar things to our wildlife and working on reserves allows us to observe the ways that nature is reacting. We had an extremely wet winter this year, the 8th rainiest since records began and on parts of the reserve the water didn’t dry out until the end of July. As a result, there have been many spawning ponds for frogs over the summer, causing a population boom. These new and improved ditches will hopefully provide spawning habitat for these extra frogs over the coming year.

A common frog on some grass. It has pale green skin with black markings on it.

Common frog

When talking about habitat improvements, it’s only fair to mention our urban herd. At Sweet Briar, we have six cows whose job is to create natural disturbances. They break up the ground, create large patches of short-cropped vegetation, and even munch on small willow trees. This is beneficial in the same way as chroming—it lets light in.

Smaller species that can’t compete with taller plants get a chance to thrive in the following summer and although the taller vegetation will inevitably return, by then the cows will have moved on to another area, giving smaller species a chance to flourish. This creates a nice tidy cycle of different types of flowers and plants over the course of a year. As a result, the overall number of different plants flowering on-site increases.

A British white cow on our Sweet Briar reserve. It is white with black ears and a black nose.

Cattle on Sweet Briar

This cycle of chopping, chroming, cutting back, or cow chomping—followed by gradual regrowth—is one of the main principles guiding conservation at Sweet Briar. Some things need to be cut back temporarily to give others a chance to thrive, before everything regrows and the cycle begins anew.

The Norfolk and Norwich Naturalists’ Society has been surveying Sweet Briar over the past year, contributing to the development of a species catalogue of everything we have here at Sweet Briar. This catalogue confirms largely what we already knew, that Sweet Briar is a rich reserve, home to a wide variety of species, from rare and interesting to common flora, fungi, and insects, all of which provide a solid foundation for the ecosystem.