The burden on Nigeria, Africa’s most populous country, is around $ 1 trillion a year, according to researchers. They put the Democratic Republic of the Congo at $ 317 billion, Niger at $ 248 billion and South Africa at $ 229 billion.

Data on invasive alien species (IAS) in Africa is scarce and it was “difficult” to obtain the material for the study, said Dr. Eschen, which is why the researchers relied on estimates in some cases.

For example, weed control costs were based on the agricultural land in each country and the average wages for farm workers. The authors used openly available data from organizations such as the International Union for Conservation of Nature and the Food and Agriculture Organization of the United Nations. This was supplemented by a survey of 110 agricultural experts from 30 African countries.

For countries with insufficient data, figures from areas with similar climates were used. Western Sahara, Djibouti and Equatorial Guinea have been omitted entirely.

The study’s estimates for workers represent opportunity costs that are higher than actual wages, the authors said. Smallholder farmers and weed hunters, for example, are often run by women and children, and this work is generally unpaid. “If people didn’t have to weed IAS, they could do something else, like go to school or do some income-generating business,” said Drs. Ash trees. “While the estimate does not reflect salaries paid, it is an indication of the effort required to deal with these species.”

In order to contain the losses, governments need to be proactive, said Dr. Ash trees.

“Investing in more efficient ways to combat IAS – including preventing the further spread of new species and the further spread of established species – as well as cost-effective management of widely distributed species, such as through biological control, could reduce management costs and result in lost yields. ” he said.