Invasive bugs, plants ‘cost more’ than Africa’s GDP

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The fall armyworm. Invasive species which have been introduced to Africa by human activity are costing the continent more than its total annual economic output says new study. Copyright: CABI

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  • Species introduced by human activity are costing Africa US$3.66 trillion per year
  • Without these species, people wouldn’t have to spend time weeding
  • Cost of time spent on weeding represents 99 per cent of overall amount

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[NAIROBI] Bugs and plants which have been introduced to Africa by human activity are costing the continent more than its total annual economic output, a study says, when the lost opportunities of time spent weeding are taken into account.

So-called invasive alien species (IAS) are costing Africa’s agricultural sector economic losses estimated at US$3.66 trillion a year, according to the study.

That’s 1.5 times the value of goods and services produced – also known as the Gross Domestic Product (GDP) – of all African countries combined.

“Agriculture is the base of Africa’s economy. Emergence of IAS could jeopardise food security and expedite poverty.”

Innocent Ngare, Kenyatta University

Over 99 per cent of this cost comes from the estimated gains that could have been made if people didn’t have to spend their time weeding.

The team, comprising scientists from the Centre for Agriculture and Biosciences International (CABI, the parent organisation of SciDev.Net) centres in Africa and Europe, conducted a literature review and online survey of 110 respondents – largely working in government or research.

tuta absoluta

Credit: CABI

René Eschen, the study’s co-author and a senior scientist at CABI, says that their study reveals the extent and scale of the economic impacts of IAS in the agricultural sector in one of the least studied continents.

“The estimated annual costs of IAS to African agriculture are US$3.66 trillion, mainly as a result of time spent weeding these species in crops, due to yield losses caused by a few important pests and due to reduced income from livestock due to major alien weeds in rangelands,” he tells SciDev.Net.

Scouting for Tuta absoluta

Credit: CABI

The study, published on Thursday (20 May) in the journal CABI Agriculture and Bioscience, Eschen explains, is unique, as the cost of people spending their time weeding and the reduced income from livestock are usually not included in estimates of IAS cost.

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The estimated US$3.6 trillion cost of weeding IAS, he says, is 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. The latter is especially important as most smallholder farmers rely on manual labour for weeding their crops.

The team established that Tuta (Phthorimaea) absoluta was responsible for the highest annual yield losses at US$11.5 billion, and next was fall armyworm (Spodoptera frugiperda) at US$9.4 billion.

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“These organisms have major impacts on people’s livelihoods, because women and children spend a lot of time weeding IAS, crop yields are significantly reduced, and degradation of grassland habitats by IAS reduces livestock carrying capacity, which affects people’s income and capital,” says Eschen.

Cattle in and amongst prosopis juliflora

Credit: Rene Eschen

“Our work reveals the scale of the IAS impact as a monetary value, which is useful for decision makers.

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“Moreover, the survey revealed very limited investment in research on IAS,” he tells SciDev.Net.

Measures are needed that reduce management costs for widely present and impactful species through methods such as biocontrol.

“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,” according to Eschen.

Innocent Ngare, a post-doctoral fellow at Kenya’s Kenyatta University, School of Environmental Studies, says that with existing resources, proper governance, resource allocation monitoring, IAS can be controlled where research organisations partner with academia to attract more funding.

“Agriculture is the base of Africa’s economy. Emergence of IAS could jeopardise food security and expedite poverty,” he tells SciDev.Net.

Invasive species, according to Ngare, are wrecking farmlands. These invasions have frustrated indigenous plant species that are of benefit to communities. In fact, the cost of managing them is increasing as they ramify our ecosystems. Africa should unlock its unutilised research potential.

This piece was produced by SciDev.Net’s Sub-Saharan Africa English desk.


René Eschen and others: Towards estimating the economic cost of invasive alien species to African crop and livestock production (CABI Agriculture and Bioscience, 20 May, 2021)