News from the Secret World of The Howard Sand Plains

Relatively few people know about this special place and the amazing plants and rare toadlets that make their home here.

The Howard Sand Plains is a unique landscape approximately 30 km east of Darwin in the Northern Territory. This area, covered by Sandsheet Health vegetation, has been classified as a Site of Conservation Significance because of the unique plant and animal species found here. Rare and endangered species include the small carnivourous bladderwort plants and the rare Howard River Toadlet. 

Many threats impact the Howard Sand Plains including mining, urban development and disturbance which leads to vegetation loss and change through clearing, hydrology changes, weed competition and increased fire frequency. 

The plains cover a mere 2258 hectares of the Howard River region.

In the wet season, the landscape fills up with a shallow layer of water. Very little organic matter exists here only a deep layer of sand containing few nutrients. The plants found here have adapted over a long period of time to find nutrients elsewhere. Many of them are carnivorous, supplementing the lack of nutrients in the soil with insects and microscopic organisms.

The small flowering plants start to grow and flower as the rains set in. The greatest abundance of flowers is at the end of the wet season in April, when the area is a sea of flowers. 

The Howard Sand Plains is home to 26 species of bladderworts (Utricularia), the greatest diversity of bladderworts in Australia. One of these species, Utricularia dunstaniae has been listed as a vulnerable species at a Northern Territory level. Bladderworts take in extra nutrients through small sacs in their roots with a door-like mechanism which act like a vacuum, sucking in microscopic aquatic animals moving through the water in and above the sand. 

The site is also home to the Howard River Toadlet (Uperoleia daviesae), tiny brown frog measuring a diminutive 2cm which is endemic to the region. It can be recognised by its call and is usually active at night.  

Weed Mapping on the Sand Sheet

To help conserve this special area, we are implementing a weed mapping project in one of the defined key localities of conservation significance. This will lead to a management plan and some targeted weed management within the area. The project connects with landholders across the area to gain access and collaborate on the project. The current mapping project is made possible by support from Territory Natural Resource Management Community grants. 

A methodology has been set up to map as much of the target area as possible for weeds. This is done with a series of 22 Transects that are being walked in the defined area and three target weeds being mapped along them. Additionally, every navigable track is being driven and all weeds are mapped.

The focus weed of the mapping is Tully grass (Urochloa humidicola). This is an exotic species which has been introduced as both a pasture grass for wetter areas and a plant to stabilise drains at roadsides. It has been identified as a future threat to wetland areas and is spreading rapidly in floodplains of the rural area. It is a robust sprawling grass and quickly outcompetes the often sensitive native flora of the Sand Sheet areas. The study will start to collect baseline data of this grass species, as well as mapping the listed weeds – Mission Grass and Gamba Grass (which are more likely to be in the drier areas adjacent to the Sand Sheet). This is done with methodology recommended by, and in consultation with, the Weeds Branch of the Department of Land Resource Management. 

We have engaged a number of volunteers from the community and from Charles Darwin University, as well as being assisted by the Top End Native Plant Society. We have so far spent five days in the field collecting data in February and April. Walking transects allows us to sample areas in an even and consistent sample.

We are also mapping every navigable track – this allows us to access a greater area, but also tracks and roads are a form of disturbance and often a great presence of weeds is found along these.