Strange inhabitants of Australia's desert puddles could go extinct

There are no swarms of fish, but a wide variety of invertebrates: predatory sentinel dragonflies patrol the surface in search of prey, while "alien-like" daphnia and seed-eating algae swim in the water column. Although invertebrates pollinate plants, recycle soil organic matter and provide food for other animals, their role is hardly mentioned in the public debate about climate change - especially when it comes to freshwater species in arid regions.

A new study shows that at least 60 unique invertebrate species live in the rock pools of arid Australia. To protect them in the face of warming temperatures, scientists will need much more data.

Oases among the rocks

Rock pools are small depressions that form in rock as a result of long-term erosion. They dry up completely during the year, so life is only possible here during rain-filled periods.

In hot weather the water may only hold for a few days, in cooler months it may hold for up to several months. Eggs and cysts that have been lying in the bottom sediments for years come to life when the puddles fill. Flying invertebrates are able to purposefully find such temporary pools, travelling long distances. Because of this variability, the conditions have long remained poorly understood.

In work carried out in seven rock pools in the Gowler Range (South Australia), researchers pioneered the use of environmental DNA (eDNA). They took water samples and used DNA traces to reconstruct which organisms are present or have recently been present in the ecosystem - over roughly the last fortnight. This made it possible to do without mass capture of animals and with little or no disturbance to them.

It turned out that each pond is a unique community. In different puddles we found seed crustaceans, water fleas, water bugs, gnat larvae and other invertebrates. In a hyper-arid landscape, these "oases" are often the only places where these species can exist.

Cultural significance for indigenous peoples

The rock pools are culturally important to several indigenous groups in Australia - the Barngarla, Kokata and Wirarugu. These peoples, who are part of the Gawler Ranges Aboriginal Corporation and hold land rights in the region, have traditionally managed these water sources and continue to utilise some of the practices today.

In dry climates, these fresh water points served as key places for recreation and recharge. Some hold up to 500 litres of water and can be quite deep. Traditional methods have been developed to maintain water bodies: regular cleaning, protection from damage and pollution by animals and humans, and special knowledge of how to find such 'hidden' springs in the desert.

The threat of climate change

Between 2023 and 2024, the planet is set to reach about 1.5 °C of warming compared to pre-industrial levels for the first time. Australia is already facing the effects of global climate change: increasingly destructive fires, heat waves, droughts and floods.

For the continent as a whole, this means less frequent and more unpredictable rainfall. While large rivers and lakes are often the centre of attention, small bodies of water - such as rock pools in deserts - remain 'off the radar'.

In south and central Australia, winter rains are becoming less reliable and summer thunderstorms more erratic and short-lived. Water in small puddles dries up more quickly, and animals adapted to utilise these temporary pools find it increasingly difficult to find water when they need it.

At the same time, invasive species pressures are increasing: feral goats and camels, farm animals degrade water quality, and alien plants infest freshwater ecosystems.

Why further research is needed

Despite the obvious vulnerability of these ecosystems, little is still known about the biodiversity of rock pools. Without this basic knowledge, it is difficult for governments and conservation organisations to develop effective protection measures and prevent further species loss.

The authors emphasise that this research is an important first step: it provides a starting point for assessing freshwater biodiversity in desert reservoirs. Understanding exactly what unique organisms live in these remote oases will help build better conservation strategies in a rapidly changing climate.