NEWS
South Africa’s invasive species
guzzle precious water and cost
US$450 million a year
The country’s pioneering first report on its biological invaders
paints a dire picture for resources and biodiversity.
Sarah Wild
Reprinted From: https://go.nature.com/2BYanym
S
outh Africa is losing its battle
against biological invaders, accord-
ing to the first attempt by the gov-
ernment to comprehensively assess the
status of the country’s alien species.
The invaders, including forest-munch-
ing wasps, hardy North American bass
and trees attractive to mosquitoes, cost
the country approximately 6.5 billion
rand (US$450 million) a year and are re-
sponsible for about a quarter of its bio-
diversity loss. That’s the conclusion of a
pioneering report that the South African
National Biodiversity Institute in Preto-
ria released on 2 November.
Invasive species also guzzle a substan-
tial amount of South Africa’s water, a
serious problem in a country suffer-
ing from a prolonged and catastrophic
drought that is expected to worsen as
the climate changes.
The report, which the institute com-
piled in response to 2014 regulations
that mandate a review of invasive spe-
cies every three years, examines the
pathways by which these species enter
the country and the effectiveness of in-
terventions. It also weighs the toll they
take on the nation’s finances and biodi-
versity.
This achievement constitutes a “signifi-
cant advance” compared with efforts by
most other countries, says Piero Geno-
vesi, who chairs the invasive species
specialist group of the International Un-
ion for Conservation of Nature in Rome.
He says that other reports have looked
at the impact of biological invasions, or
at measures to address the problem,
but they have not considered all aspects
of invasions.
Helen Roy, an ecologist at the Centre
for Ecology and Hydrology near Oxford,
UK, says that, to her knowledge, this is
09
Figure 1: The invasive ant Linepithema humile disrupts seed dispersal in indig-
enous South African plants. Credit: Mark Moffett/Minden Pictures/Alamy
the first comprehensive synthesis of the
state of invasive species by any coun-
try. The report provides “an incredible
basis” on which to build predictive ap-
proaches to invasive species that could
be used to inform prevention strategies
in South Africa, she says.
Climate change
Across the world, invasive alien species
— organisms that have been introduced
into ecosystems beyond their natural
habitats, and that spread over large dis-
tances on their own — are considered
a major threat to biodiversity, human
health and economies. Climate change
is expected to further their spread
around the world, in part by reducing
the resilience of native ecosystems. In
2015, 37 researchers from 14 national
organizations, led by the National Bio-
diversity Institute and the Centre of Ex-
cellence for Invasion Biology at Stellen-
bosch University, began compiling the
South African report. The researchers
collated data from agencies and institu-
tions around the country to measure the
different aspects of biological invasion.
They report that 7 new species are intro-
duced into South Africa each year, and
that about 775 invasive species have
been identified so far. This contrasts
Grassroots
Vol 19
No 1
March 2019