Invasive alien species introduced by human activity are costing African agriculture industry an estimated Kes.385 trillion ($3.6 trillion) a year, a new study shows.

Scientists from Kenya, Ghana, Britain and Switzerland found that these non-native species of weeds, insects or worms have catastrophic effects on farming with just a single bug capable of drastically reducing yields of staple crops across the continent.

In their first comprehensive study on the economic impact of a range of invasive alien species (IAS), the scientists report that the average cost of IAS per country was $76.32 billion.

Kenya’s total estimated costs by invasive alien species stood at $93,357 million.

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The study, Towards estimating the economic cost of invasive alien species to African crop and livestock production published in the journal CABI Agriculture and Bioscience, was conducted through literature review and online survey of 110 respondents largely working in government or research.

Tuta absoluta caused the highest annual yield losses at $11.45 billion, followed by the fall armyworm at $9.4 billion.

The research took account of yield losses of major crops including maize, tomato, cassava, mango and banana ($82.2 billion), as well as labour costs – through weeding ($3.63 trillion) – and loss of income derived from livestock ($173 million).

The annual impact of IAS – that also included Prostephanus truncatus, Bactrocera dorsalis and banana bunchy top virus – was highest on cassava ($21.8 billion), followed by citrus fruits ($14.6 billion), tomato ($10.1 billion), maize ($9.8 billion) and banana ($7.1 billion).

Lead author Dr René Eschen said, “the results highlight the need for measures that prevent new species from arriving and established species from spreading, and that reduce management costs for widely present and impactful species through methods such as biocontrol.”

Co-author, Dr Bryony Taylor said, “the results of this study provide policy makers with the evidence needed to enable prioritisation of management measures for IAS, thereby reducing costs in the long term.”

The study comes after a policy summit on invasive species held in 2019, where policymakers, research, the private sector and civil society across Africa resolved to develop a strategy and action plan to fight against IAS.

In response to the findings, Dr Dennis Rangi, Director General, Development, CABI, said, “an estimated $3.6 trillion a year impact of invasive alien species on Africa’s agricultural sector is a tremendous loss where over 80 per cent of people living in rural areas rely on the crops they grow for food and income.

“The long term effects are exacerbated by COVID-19 which continues to apply intense pressure on an already fragile agricultural sector and food supply chain. Notably, governments across the continent put in place mitigation measures to manage the pandemic and its impact. Kenya for example proposed a $503 million economic stimulus in 2020 to cushion its citizens.

“Under the African Union’s stewardship, countries now have a Strategy for Managing Invasive Species in Africa. The 2021-2030 strategy provides a framework for all relevant stakeholders at the Continental, Regional and National level can use to sustainably prevent and eradicate invasive species in Africa.”

Ambassador Madam Josefa Sacko, Commissioner for Agriculture of the African Union Commission, said, “we cannot transform African agriculture if we do not pay special attention to the management and control of invasive alien species. It’s time to act and walk the talk.

The AU Commission is providing a coordination mechanism for the implementation of the strategy for managing IAS by providing strategic guidance, facilitating domestication and implementation of the strategy, plus seeking support from partners across the continent.

Currently in its first year of roll out, the invasive alien species strategy prioritises the establishment in 2022 of continental, regional and national emergency funding mechanisms for rapid action against IAS.

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