Digging into the dry wetlands of the Northern Cape

By Dr Betsie Milne, Postdoctoral Fellow, SAEON Arid Lands Node Tweet

Wetlands in drylands

When travelling from Kenhardt to Calvinia in the Northern Cape Province, thousands of blue blots on the road map stagger the mind, all representing waterbodies in a very dry landscape.

Dr Betsie Milne is a Postdoctoral Fellow who recently joined the SAEON Arid Lands Node

Most travellers will encounter the desiccated bare surfaces and associated dust plumes of these waterbodies along the way, while only a few will be fortunate enough to see them come alive after a good rainfall event.

These waterbodies, colloquially known as “pans”, are abundant features in arid regions. They differ from the familiar wetlands in humid regions, which are continuously inundated systems with saturated soils, by only being inundated every few years.

A wetland resurrection

When pans become inundated after sufficient rainfall, invertebrates like branchiopods and dipterans hatch out and algae are reactivated. Wildlife, especially water birds, gathers to feast in the resurrected systems. These events are short-lived due to the high evaporation rates of the region and therefore organisms are well adapted to rapidly benefit from favourable conditions and ensure genetic continuity.

As the variable scale of wetness over space and time and the unpredictable rainfall regime challenge consistent sampling protocols during wet spells, these systems are misunderstood and the conservation and management approaches uncertain. By contrast, these pans are possibly among the most sensitive ecosystems in the region, potentially supporting many species of conservation significance and possibly acting as key ecosystem features for temporarily dormant and migrant species.

A desiccated pan characterised by polygonal surface cracks (Photo: Betsie Milne)

Anthropogenic influences

The pans of the Northern Cape are subject to various threats, including livestock agriculture, crop farming, salt mining, damming, ploughing to enhance infiltration, alien invasion, recreational activities and speed record attempts.

The recent shift of development focus to the province in terms of uranium mining, fossil fuels, renewable energy and radio astronomy has not only increased anthropogenic pressure on the wetland ecosystems, but subsequently revealed the immense necessity to fill the knowledge deficit for the region, especially in the field of freshwater ecology.

An inundated pan (photo: Betsie Milne) with inserts showing dipteran larvae (L), Anostraca (C) and Triops (R) (Photos: Joh Henschel)

Digging into the pans

Dr Betsie Milne recently joined the SAEON Arid Lands Node as a DST-NRF Professional Development Programme^* Postdoctoral Fellow. She intends to characterise ephemeral pans in the Northern Cape Province by using remote sensing and in-situ sampling protocols so as to establish a long-term monitoring framework.

By studying the biodiversity of pans and their structure and functioning, it will be possible to evaluate the significance of impacts and changes in these systems in relation to global and land use change.

A pan ploughed by the landowner to increase infiltration (Photo: Joh Henschel).

This project will achieve ground-breaking research into the scant knowledge pool regarding ephemeral pans of the Northern Cape. It will allow the SAEON Arid Lands Node to provide much-needed information to land managers and decision makers on the management and conservation of these pans.

^* The Professional Development Programme of the Department of Science and Technology and the National Research Foundation aims to accelerate the development of scientists and research professionals in key research areas.