Introducing Cloudy Bay Peatland Swamp, Bruny Island, Tasmania

In late 2024, NGT was contacted by a landholder in the south of Bruny Island, who had recently purchased a 20-hectare property east of Cloudy Bay Lagoon, intending to restore the former grazing land and manage the site into the future for conservation.

The property consists of cleared areas of Scented Paperbark (Melaleuca squarrosa) scrub and Messmate Stringybark (Eucalyptus obliqua) forest. A small, informal drainage line flows from a higher elevation in the east of the property, towards the southwest and exits the south. This drainage line has been channelised and cut into the peaty substrate in an attempt to dry out the surrounding peatland and facilitate grazing. The channel is 1m deep and up to 450m long. These works are understood to have been undertaken by the previous landowner, with the first period of clearing and channel cutting undertaken in 2005, and clearing recurring in 2013.

A substantial volume of peat sediment underlies the paperbark swamp. Where hydrology is intact, in the upper reaches of the property, it represents one of the tallest, healthy Melaleuca/tea-tree peat swamps I have seen, with tree fern understorey. The ground here is spongy, saturated, black peat, and covered in shady, mature vegetation.

However, where hydrology has been interrupted by the artificial channelisation of flows, the dried peatland resembles a huge, open field of crumbly potting mix, which is now rapidly breaking down as a result of prolonged dehydration.

This area is succumbing to significant rill erosion (where channels form across the surface), susceptible to fire and risks being an ongoing major source of carbon emissions, as it oxidises to the atmosphere. The drain is causing both surface and subsurface flows to rapidly bypass this down-gradient, dehydrated peatland area.

Peat swamps require near-permanent saturation of the subsurface profile to maintain their healthy function, including supporting a wide range of important ecosystem values and services.

Areas that were cleared but still have some contact with shallow groundwater have started to recover in the last 10 years, while those that subsequently dried out have not. For example, Gahnia, Melaleuca, and hop bush have regenerated in the cleared south-eastern section, while sections of dried peat in the area down-gradient of the drain have no cover and are actively eroding.

We have developed a restoration plan in consultation with the landholder. The plan aims to restore the site by infilling the artificial channel, to immediately re-hydrate the peatland, stimulate rapid and spontaneous vegetation recovery, and reinstate natural flows. The large amount of spoil generated during drain construction remain in place on the edge of the drain. This material could simply be pushed back into the drain from where it came.

We also propose to monitor recovery of the subsurface water levels and vegetation through the installation of a transect of shallow monitoring wells in conjunction with a vegetation monitoring transect.

This site can potentially become a valuable demonstration site for landholders of drained peatlands elsewhere, as NGT looks to upscale the restoration of peatlands throughout south-eastern Australia. Note that drainage of peatlands is one of the largest contributors to global land-based carbon emissions. This is because peatlands go from typically being carbon sinks to carbon sources after artificial drainage removes permanent saturation.

Together with the landholder, NGT is currently on the lookout for an appropriate funding opportunity that will enable us to bring these restoration plans to fruition. This will enable us to re-saturate the peatland and set it on a trajectory of recovery for decades to come.

In the face of a changing climate, reversing the artificial drainage of peatlands is an important action that will:

(a) lead to a spontaneous biodiversity response.
(b) protect our fresh groundwater resources, and
(c) help to mitigate carbon emissions worldwide.