THIS FEATURE IS FROM VELD & FLORA SEPTEMBER ISSUE 107(3), PAGES 20-21

#KNOW

​​SA Biodiversity Update: Know your enemy

If we don’t stop biological invasions of South Africa, we lose our biodiversity

NOV 17, 2021 | BY ZIMKITA MAVUMENGWANA & RUQAYA ADAMS. PHOTOGRAPHS BY JOHN WILSON AND TREVOR XIVURI

Above: Monitoring fringed wattle (Acacia fimbriata) as part of an eradication attempt. Photo: John Wilson

BE PROUD, SOUTH AFRICA! We have the world’s only country-level assessment that focuses specifically on biological invasions and their management, says Barbara Creecy, Minister of Forestry, Fisheries and the Environment.

“It is an important element of South Africa’s global leading position on this issue,” she adds.
In late May this year, the minister launched the second comprehensive report, assessing the 2019 status. The first report covered the 2016 situation. They both contribute to developing new policy on managing biological invasions.

HISTORY OF HARM

One of the most recent and most damaging new invasive species is polyphagous shot hole borer. This borer species and its associated fungus have already killed thousands of trees in South Africa’s streets, gardens, protected areas and orchards. They threaten millions more.

South Africa’s wide range of climate zones means a wide variety of species can usually find a suitable area in the country. Then populations of these introduced species often explode here, causing biological invasions – which are responsible for loss of 25% of South Africa’s delicate biodiversity.

Today, species coming into South Africa’s ports of entry are checked with new technologies such as DNA analysis to prevent introduction of harmful species.

Biological invasions blight human livelihoods, from agricultural productivity and loss to the medicinal plant industry to damage to infrastructure and dropping property values. Despite Working for water creating some jobs nationally for local people clearing alien plant species, the invasions’ impact obstructs South Africa’s socio-economic development.

COST OF DAMAGE CONTROL

Controlling these foreign plants and animals has cost the South African government more than R1–billion a year since 2013. Current estimates suggest the true ecological cost of invasive alien plants and animals is more than R6.5 billion a year in water, grazing and other services taken from our ecosystem.

Plant and animal species from other countries have been brought into South Africa for more than two centuries. Not all alien plants and animals become invasive and have negative impacts. Most plants known to have been introduced here were destined for horticulture and/or as ornamentals.

South Africa’s ecosystems are naturally mainly treeless but until the mid-20th century, tree species were brought in to fill this gap, establish commercial forestry and to provide wood. Even most alien plants introduced to national parks were intentionally planted as ornamentals. Others were dispersed by rivers and animals.

Above: Pretty but poisonous – Paterson’s curse (Echium plantagineum), originally indigenous to western and southern Europe, invades cultivated land, pastures and roadsides in South Africa. Photo: SANBI

FIGHTING FIRES

Invasive trees use between 3% and 5% of South Africa’s surface water runoff each year – water we cannot spare in an already water-scarce country also increasingly prone to drought. Cape Town’s water crisis of 2015 to 2018 was made significantly worse by invasive trees sucking up water. Similar effects are experienced in other drought-stricken areas, such as the Eastern Cape.

The destructive 2018 Knysna wildfires were intensified by invasive plants. In plant-invaded areas, fires were more severe, thwarting attempts to contain fires – and 15% more fuel from trees and brush was burned.

Invasive plants reduce the value of livestock produced on natural rangelands by R340 million per year, an amount that will grow rapidly if invasions are not controlled. Current estimates are that if we do not control biological invasions on grazing land, we could lose up to 70% of this valuable natural asset, threatening rural livelihoods and food production.

ON THE FRONT LINE

Biological invasions impact almost every ecosystem in South Africa. Several of South Africa’s protected areas are severely invaded but not yet all. Heartbreakingly, the highest increase in the number of invasive species has been in South Africa’s land of plant treasures, fynbos.
You can help by providing information on locations of alien species through citizen-science platforms such as iNaturalist and SABAP, as well as volunteering
with your local hacking group.

Above: Boxing-glove cactus (Cylindropuntia fulgida var. marmillata) invades veld outside Groblershoop in the Northern Cape. Photo by Trevor Xivuri