Some South African plants and animals caused harm in foreign countries

Over 600 foreign species of plants and animals have invaded South Africa, but only 34 South African species have invaded other countries. This is according to researchers who, for the first time, documented native South African species exported to other countries.

Invasive species include plants and animals not native to an area, which may overpopulate and harm that area. 

Throughout history, humans have brought species native to one country into other countries where they were not naturally found. Until now, little was known about how many South African species had been taken to other parts of the world, and how this number compares to the number of foreign species brought into South Africa from other countries.

Researchers used public information to make a list of all the species from South Africa that were found in other parts of the world, and they interviewed experts in this field. 

They found that South Africa had been invaded by 629 alien species from other countries, but only 34 South African species are found elsewhere in the world. Most of these are animals - several monkeys and birds, for instance, are found in zoos in other countries.

South Africa is also responsible for a “bridgehead effect”, which is when foreign animals or plants that are introduced become established in their new country, but then become a source of invasion in other countries. 

As an example, crayfish were introduced into South Africa in the 1970’s, but they were then  introduced to other neighbouring Africa countries like Swaziland, Zambia and Mozambique, both intentionally and accidentally. The same happened with fish species like trout, carp and basses that were introduced into Swaziland, Lesotho, Zimbabwe and other countries. 

Researchers also found that 3 species were traded by people who wanted African animals in their countries. The introduction of these species in those countries was considered invasive, because they harmed local species. 

The rest of the species were not as invasive and could have been introduced accidentally through transport. For instance, insects usually found on African trees were spotted in southern Europe. The researchers said these could have been transported there on wood or on people’s clothing or bags.

They found that frogs, specifically  Xenopus laevis, moved around other Africa countries and from South Africa. They were being used for research in different places and some of them may have escaped and bred with other frog species. 

The frogs were also transported to other countries to be kept as pets, and in fact many other South African species were exported to become “exotic” pets in other countries. These include wild animals like frogs, toads and geckos, which are not usually kept as pets.

The researchers also said  several mammals, reptiles, birds and fish were taken to other countries for sports hunting. Some of these were advantageous to these countries for tourism, while others have invaded their surroundings.  

Despite their best efforts, the researchers cautioned that they could not be 100% certain that all the animals they reported on were originally from South Africa.

They said however that this research supports the need to control the spread of invasive species that can cause harm in places that they are not native to.

The authors of this study were from South Africa.

Abstract

This review provides the first assessment of animal species that are native to South Africa and invasive elsewhere in the world. While around a twelfth of all naturalised plants in the world are native to South Africa, there are very few examples of South African native marine, terrestrial, or freshwater animals becoming invasive elsewhere. We provide a narrative of each of the 34 cases that we could find.Threeofthesespecies,theCommonWaxbill,Estrilda astrild,theMozambique Tilapia, Oreochromis mossambicus and the African Clawed Frog, Xenopus laevis, were widely traded, and introduced on several continents with invasive populations becoming the subject of substantial research. Most other species are poorly documented in the literature such that it is often not known whether South African populations are the source of invasions. These species demonstrate the same trend in pathways of animals entering South Africa, moving from deliberate to accidental through time. The role of mavericks, individuals whose deliberate actions wilfully facilitate invasions, is highlighted. While South Africa has acted as an important bridgehead for the invasions of forestry pests, crayfish, fish and amphibians on the continent, it is clearly not a major donor of animal invasions, but rather a recipient. This could be due to South African ecosystems being fundamentally more invasible, or South African fauna showing reduced invasiveness, though it is likely that substantial differences in historical pathways also played a crucial role.

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