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CABI scientists have conducted the first comprehensive study on the economic impact of a range of Invasive Alien Species (IAS) on Africa’s agricultural sector, which they estimated to be USD $65.58 billion a year.

This is equivalent to 2.5% of the gross domestic product of all African countries combined.

The average annual cost of IAS per country was USD $1.37 billion. Full details of the cost for individual countries are outlined in the paper published in the journal CABI Agriculture and Bioscience.

The team, comprising scientists from CABI centres in Africa and Europe, conducted a thorough literature review and online survey of 110 respondents – largely working in government or research – and established that the fall armyworm (Spodoptera frugiperda) caused the highest annual yield losses at USD $9.4 billion.

The research took account of yield losses of major crops including maize, tomato, cassava, mango and banana (USD $82.2 billion), as well as labour costs – through weeding (USD $36.34 billion) – and loss of income derived from livestock (USD $173 million).

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

Lead author Dr René Eschen said, “This study reveals the extent and scale of the economic impacts of Invasive Alien Species in the agricultural sector in one of the least studied continents.

“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. This will potentially reduce future production costs, lower yield losses and improve the livelihoods of farmers and other affected land users.”

Co-author, Dr Bryony Taylor, said, “We have added to the knowledge base of the costs of Invasive Alien Species to Africa’s agricultural sector by including all countries within the continent where previous research only included a few.

“We also include the cost of reduced livestock-derived income and research and labour costs, which are generally not included in estimates of the costs of Invasive Alien Species.

“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.”

Fernadis Makale, another co-author on the paper, said, “The large estimate for the weeding costs may come as a surprise but this work, often carried out by women and children, is never measured as part of the African economy.

“Moreover, it should not be concluded that people are being paid that amount as salaries. Rather, the estimate represents an opportunity cost, meaning that if people didn’t need to weed IAS could do something else, such as going to school or undertaking an income generating economic activity.

“In addition, our study provides evidence of the need for country and regional quarantine and phytosanitary measures to prevent the entry and spread of new IAS, preventing additional, potentially huge costs as new IAS spread across the continent.”


Loss of income derived from from livestock is USD $173 million (Credit: Rene Eschen).

The study comes after a policy summit on Invasive Species held in 2019, where 70 delegates, representing policymakers, research, the private sector and civil society from across Africa, resolved to develop a strategy and action plan to fight against Invasive Alien Species.

In response to the findings, Dr Dennis Rangi, Director General, Development, CABI, said, “An estimated USD $65.58 billion a year impact of Invasive Alien Species on Africa’s agricultural sector is a tremendous loss where over 80% 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 USD $503 million economic stimulus package in 2020 to cushion its citizens.

“This is the same resolve, urgency and investment our Governments need to channel towards managing the Invasive Alien Species problem.

“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.”

H.E Ambassador Madam Josefa Sacko, Commissioner for Agriculture, Rural Development, Blue Economy and Sustainable Environment of the African Union Commission, said, “From this research, it is clear that Invasive Alien Species pose a devastating impact on Africa’s agricultural sector with a direct consequence on the achievement of the four commitments listed in the Malabo declaration. 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 (AUC) is providing a coordination mechanism for the implementation of the strategy for managing Invasive Alien Species at the continental level. This also includes providing strategic guidance, facilitating domestication and implementation of the strategy, plus seeking support from partners across the continent.

“Managing Invasive Alien Species is an absolute imperative if Africa’s agriculture is to meet its full potential and feed its growing population – which is expected to double to 2.5 bn people by 2050 – and contribute towards global food security,” added Madam Sacko.

Currently in its first year of implementation, the Invasive Alien Species strategy outlines six key areas of focus under its 2021-2025 action plan. One of the priority areas is the establishment in 2022 of continental, regional and national emergency funding mechanisms for rapid action against Invasive Alien Species.


Notes to editors

Main image: The fall armyworm was responsible for the highest annual yield losses at USD $9.6 billion (Credit: CABI).

Full paper reference

René Eschen, Tim Beale, J. Miguel Bonnin, Kate L. Constantine, Solomon Duah, Elizabeth A. Finch, Fernadis Makale, Winnie Nunda, Adewale Ogunmodede, Corin F. Pratt, Emma Thompson, Frances Williams, Arne Witt, Bryony Taylor, ‘Towards estimating the economic cost of invasive alien species to African crop and livestock production,’ CABI Agriculture and Bioscience, 19 August 2021, DOI: 10.1186/s43170-021-00038-7

Correction to paper

This paper has been corrected after the identification of two errors. The first error was in the calculation of weeding costs in which the wage costs of weeding per square kilometre were applied instead per hectare. The recalculation estimates the total cost of invasive alien species to the African agricultural sector as $65.58 billion per year not, as originally stated, $3.66 trillion. This is equivalent to 2.5% of the gross domestic product of all African countries combined, rather than the originally stated 150%. The second error was in the calculation of the crop loss due to Phthorimaea absoluta in which the value was not corrected for the abundance of this species within each country. The recalculation estimates that this species costs the agricultural sector $4.1 billion in crop losses per year, rather than the originally stated $11.4 billion. Further details can be found in the correction text.

The corrected paper is available to view here:

Funding acknowledgement

The research was financially supported by the Foreign, Commonwealth & Development Office (FCDO), UK, and the Directorate‐General for International Cooperation (DGIS), Netherlands, through CABI’s Action on Invasives programme. CABI is an international intergovernmental organisation, and we gratefully acknowledge the core financial support from our member countries (and lead agencies) including the United Kingdom (Foreign, Commonwealth & Development Office), China (Chinese Ministry of Agriculture and Rural Affairs), Australia (Australian Centre for International Agricultural Research), Canada (Agriculture and Agri-Food Canada), Netherlands (Directorate-General for International Cooperation), and Switzerland (Swiss Agency for Development and Cooperation). See for full details.

Other relevant research

This research builds upon previous CABI evidence notes on the impacts of invasive alien species including:

Tuta Absoluta Evidence Note 2019

Parthenium Evidence Note 2019

Fall Armyworm Evidence Note 2017

Find more information about CABI’s work on invasive species here.

Media enquiries

Dr René Eschen, Senior Scientist, Ecosystems Management, and Risk Analysis and Invasion Ecology, email:

Dr Bryony Taylor, Senior Project Scientist and Project Manager, email:

David Onyango, Communication Specialist (Kenya based), email:
Tel: +254 (0)20 2271000/20

Wayne Coles, Communications Manager (UK based), email:

About CABI

CABI is an international not-for-profit organization that improves people’s lives by providing information and applying scientific expertise to solve problems in agriculture and the environment.

Through knowledge sharing and science, CABI helps address issues of global concern such as improving global food security and safeguarding the environment. We do this by helping farmers grow more and lose less of what they produce, combating threats to agriculture and the environment from pests and diseases, protecting biodiversity from invasive species, and improving access to agricultural and environmental scientific knowledge. Our 50 member countries guide and influence our core areas of work, which include development and research projects, scientific publishing and microbial services.

We gratefully acknowledge the core financial support from our member countries (and lead agencies) including the United Kingdom (Foreign, Commonwealth and Development Office), China (Chinese Ministry of Agriculture and Rural Affairs), Australia (Australian Centre for International Agricultural Research), Canada (Agriculture and Agri-Food Canada), Netherlands (Directorate-General for International Cooperation, and Switzerland (Swiss Agency for Development and Cooperation). Other sources of funding include programme/project funding from development agencies, the fees paid by our member countries and profits from our publishing activities which enable CABI to support rural development and scientific research around the world.