Invasive alien species are organisms that are introduced by human activities to regions where they do not naturally occur.
They can have negative impacts on the environment, economy, and human health. In Africa, invasive species threaten the food security, biodiversity, and livelihoods of millions of people.
According to a new report by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), invasive alien species are one of the five most important direct drivers of biodiversity loss globally, and their economic cost exceeds US$423 billion annually.
The report also provides policy options and recommendations for preventing and managing invasive alien species.
Here are four key messages from the report that African countries should heed if they want to successfully tackle the threats posed by invasive species.
A major threat to nature, its contributions to people, and good quality of life
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Invasive alien species can affect ecosystems in various ways, such as competing with native species, preying on them, spreading diseases, altering habitats, and disrupting ecological processes.
For example, the introduction of the Nile perch, Lates niloticus, into East Africa's Lake Victoria in 1954 caused the extinction of approximately 200 species of cichlids from the lake.
It also resulted in the lake becoming enriched with nutrients as people came to fish for Nile perch, which led to the invasion of water hyacinth.
Water hyacinth is an aquatic plant that forms dense mats on the surface of water bodies, blocking sunlight, oxygen, and navigation. It also reduces fish production, agricultural productivity, grazing, and water supplies.
Invasive alien species can also have negative impacts on human well-being, such as affecting food security, health, culture, and recreation.
For instance, the Asian citrus greening disease or huanglongbing (HLB) is a bacterial disease that affects citrus trees and reduces their fruit quality and yield. It is transmitted by an insect vector, the Asian citrus psyllid.
HLB was first detected in Africa in 1943 in Ethiopia and has since spread to several other countries in East and Southern Africa.
HLB threatens the citrus industry in Africa, which provides income and employment for millions of people. HLB also affects the availability and affordability of citrus fruits for consumers.
Increasing in number and spreading rapidly
The report estimates that more than 37,000 alien species have been introduced by human activities to regions and biomes around the world, most in the past 100 years.
The main pathways of introduction include trade, transport, tourism, agriculture, aquaculture, forestry, horticulture, and landscaping.
Human activities facilitate the movement of organisms across natural barriers such as oceans, mountains, and deserts.
Environmental changes, such as climate change, land use change, habitat fragmentation, pollution, and natural disasters can also facilitate the establishment and spread of invasive alien species.
For example, climate change can create new opportunities for invasive species to invade areas that were previously unsuitable for them due to temperature or precipitation limits.
Climate change can also increase the vulnerability of native species and ecosystems to invasion by reducing their resilience and adaptive capacity.
It is native to Asia but has expanded its range to many parts of the world due to global warming and human-mediated dispersal. It is now present in several African countries, where it poses a risk to public health.
Prevention requires international cooperation and coordination among countries, as well as regional and global agreements and conventions.
For example, the Convention on Biological Diversity (CBD) is an international treaty that aims to conserve biodiversity and ensure its sustainable use.
The CBD has a specific program of work on invasive alien species that provides guidance and support to countries on how to prevent and manage them.
When prevention fails, early detection and rapid response are crucial to eradicate or contain invasive alien species before they become widespread and cause irreversible damage.
Prevented and managed through collective action
The report highlights that invasive alien species are not a natural phenomenon; they are a consequence of human activities that can be avoided or minimized through collective action.
Collective action involves engaging and empowering all relevant stakeholders, such as governments, civil society, the private sector, indigenous peoples, local communities, researchers, practitioners, media, and the general public.
It requires enhancing awareness and understanding of the causes, consequences, and solutions for invasive alien species among all stakeholders.
Moreover, it also requires strengthening the scientific basis and knowledge gaps on invasive alien species, as well as improving the access and sharing of data and information.
Fostering collaboration and partnerships among stakeholders at different levels, from local to global, and across different sectors, such as environment, agriculture, health, trade, and transport, is another way.
Lastly, doeveloping and implementing coherent and consistent policies and regulations on invasive alien species, as well as mainstreaming them into other relevant policies and plans is another requirement.
