Invasive alien species threaten agriculture and biodiversity in Africa: Study

Africa may lose about $3.66 trillion annually due to impact of IAS on agriculture

By Madhumita Paul
Published: Tuesday 22 February 2022
Invasive alien species threaten agriculture and biodiversity in Africa: Study Photo: iStock

Invasive alien species (IAS) of plants, animals and microbes lead to losses running up to billions of dollars annually in every part of the world, particularly in sub-Saharan Africa, according to a new report. The region has seen the arrival of many IAS in recent years.

IAS cause yield loss, resulting in serious negative impacts on livelihoods. They are also responsible for the extinction or decline of many species. 

Africa may lose about $3.66 trillion annually from the impact of the IAS on agriculture and other vital food production programmes, a 2021 study showed

The International Union for the Conservation of Nature defines an alien species as a species introduced outside of its natural range. They may be brought in by people accidentally or intentionally into regions where they do not exist. 

There are around 18,000 invasive alien species around the world, according to another study by an international team of scientists from 13 countries. 

The new study was conducted in Ghana on nearly 200 potentially harmful alien plant species that can affect agriculture, forestry and biodiversity. It was led by the Centre for Agriculture and Bioscience International and published in the journal NeoBiota

The objective of the study was to employ horizon scanning to establish a list of potentially invasive alien plant pests (arthropods, including insects and mites and pathogens, including fungi, bacteria and nematodes) that may be harmful to Ghana’s agriculture, forestry or biodiversity if introduced.

The aim of the study was to enable prioritisation of actions, including pest risk analysis, prevention, surveillance and contingency plans. It can serve as a model for future projects on plant pests’ prioritisation in Africa and elsewhere, researchers said.

The prioritisation was carried out by a panel of 23 subject matter experts from Ghana research institutions and academia. The prioritisation was carried out using an adapted version of horizon scanning and consensus methods. 

A total of 110 arthropod species (101 insects and nine mites) and 64 pathogenic species (14 bacteria, 16 fungi, 14 nematodes, seven water moulds and 13 viruses) were assessed. 

Two of the 64 pathogenic species, Moniliophthora perniciosa and Moniliophthora roreri, had not been reported anywhere in Africa at the time of assessment, leaving 62 pathogenic organisms with a presence in Africa. 

Among the top arthropods prioritised by researchers were the pink hibiscus mealybug (Maconellicoccus hirsutus Green) and melon thrips (Thrips palmi Karny). The top pathogens highlighted include cassava brown streak virus and Maize lethal necrosis disease.

Cassava in Ghana, for example, is a main staple crop and contributes about 22 per cent and 30 per cent to the agricultural gross domestic product and daily calories intake, respectively. The crop can be at risk from cassava brown streak virus which can reduce yields by up to 70 per cent.

Maize lethal necrosis disease can be a major disruptor of maize production in Ghana, where the crop accounts for more than 50 per cent of the country's total cereal production. The disease can cause losses ranging between 50-90 per cent, depending on the variety of maize and the growing conditions of the year, the report showed.

The scientists also found other species recorded in Africa that included 19 arthropod and 46 pathogenic species, which were already recorded in the neighboring countries of Burkina Faso, the Ivory Coast and Togo. 

The majority of arthropod species were likely to arrive as contaminants on commodities and also could arrive as stowaways in cargo from other countries around the world, according to the study.

Subscribe to Daily Newsletter :

Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.