On the trail of rare orchids in New South Wales

Protecting Diuris arenaria: our approach

In many cases we’re dealing with plants and animals that people know and recognise. Occasionally though, our work involves documenting and managing impacts for ultra-rare species. One such plant that we’ve been looking at recently is the endangered terrestrial orchid, Diuris arenaria.

More commonly known as ‘Sand Doubletail’, Diuris arenaria exists in a highly restricted zone around the coastal parts of Port Stephens, New South Wales. Listed as ‘endangered’, its vital that activity in areas where Diuris arenaria could be present is managed with the utmost care.

But what does it take to safeguard the future of Australian native flora like the Sand Doubletail? As we head into spring, here is how the RPS ecology team in Newcastle is approaching our work on the trail of Diuris arenaria.

Step 1: Planning a survey – look at a reference population

When we are assessing whether a particular plant species may be present—especially those that can only be found and identified in a small time window when they flower—it’s important to identify the optimum time in the plant’s flowering cycle to commence a site survey. Timing is everything!

Before we start to look for Diuris arenaria in a new area, we need to know when it will be in peak flower. This can vary year-on-year due to temperature, rain and other factors.

This is where the reference population comes in. It helps us understand what’s happening in a known population at a particular time of year. We use this information to determine the best time to complete survey work on a subject site.

Checking the reference population also helps us to better understand the ideal conditions for Diuris arenaria.

What is the ideal habitat? What types of vegetation and soils are present where these orchids are growing? And what other species can we typically see present alongside them?

Step 2: the orchid search begins

After observing the orchids flowering at our reference site and deciding that the time is right to survey, we need to mobilise quickly. In the case of Diuris arenaria, there are specific requirements for how we complete field studies as specified in the Surveying threatened plants and their habitats: NSW Survey Guide for the Biodiversity Assessment Method.

Our team systematically traverses the area by foot (parallel transects), which are tracked and logged with a GPS. In the case of an orchid, the field team needs to walk five metres apart to minimise ‘false negative’ results (the species is reported as absent from a site when it is actually present). 

Step 3: Understanding the species on our site

The traverses by foot will either result in the detection of Diuris arenaria or confirm its absence from the subject site. If detected, our team will then take steps to record its location and the number of individual plants observed.

This information is collected using GPS with high positional accuracy, to help us understand where a plant is located and how it might relate to a proposed development or activity. This information is crucial in identifying how best to avoid disturbance and manage populations into the future.

Ongoing conservation of Diuris arenaria

The endangered Diuris arenaria is identified under NSW’s Saving our Species (SoS) program as a site-managed species.

SoS is one of the biggest conservation commitments ever undertaken in by the NSW Government and is an initiative that brings scientists, businesses, community groups, volunteers and government agencies together to protect unique plants and animals.

In the case of Diuris arenaria, five management sites have been established so far for pro-active conservation efforts.

The data that we collect from our surveys such as location, time of flowering and count of individuals is reported to the NSW Government Biodiversity Conservation Division, which contributes to the government dataset. This information is critical to understanding the trajectory and habitat requirements of the species, and ultimately contributing to conservation actions.