Centre of Agriculture and Biosciences International (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 $3.6 trillion a year.

This is equivalent to 1.5 times the gross domestic product (GDP) of all African countries combined, or similar to that of Germany's.

The average annual cost of IAS per country was $76.32 billion. Full details of the cost for individual countries are outlined in a paper published in the journal CABI Agriculture and Bioscience.

The team, comprising scientists from CABI centers in Africa and Europe, conducted a thorough literature review and online survey of 110 respondents — largely working in government or research — and established that Tuta (Phthorimaea) absoluta (tomato leafminer) caused the highest annual yield losses at $11.45 billion, followed by the fall armyworm (Spodoptera frugiperda) 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 (BBTV) — 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, "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 labor 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 prioritization 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 [they] 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."

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 of development at 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% 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 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 (AU's) stewardship, countries now have a Strategy for Managing Invasive Species in Africa. The 2021-2030 strategy provides a framework [that] 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 for the African Union Commission (AUC), 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 [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 billion 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.

Funding acknowledgement

The research was financially supported by the U.K.'s Foreign, Commonwealth & Development Office (FCDO) and the government of the Netherlands' Directorate‐General for International Cooperation (DGIS) through CABI’s Action on Invasives program. CABI is an international intergovernmental organization, and we gratefully acknowledge the core financial support from our member countries (and lead agencies) including the United Kingdom (FCDO), China (Chinese Ministry of Agriculture and Rural Affairs), Australia (Australian Centre for International Agricultural Research), Canada (Agriculture and Agri-Food Canada), Netherlands (DGIS) and Switzerland (Swiss Agency for Development and Cooperation). See https://www.cabi.org/about-cabi/who-we-work-with/key-donors/ for full details.