Invasive Alien Species: A Dual Threat to Biodiversity and Economies

Invasive species of plants and animals threaten indigenous species but can also cause broader harm. Photo: Mariya Ivanova
Invasive species of plants and animals threaten indigenous species but can also cause broader harm. Photo: Mariya Ivanova

By Francesco Ricciardi

The silent invasion by invasive alien species, including plants, invertebrates, vertebrates and microorganisms, is jeopardizing biodiversity and economies on a global scale. We need to take urgent, coordinated action.

In a world shaped by globalization and interconnectedness, a silent alien invasion is spreading. It is not coming from outer space, but from the Earth’s own ecosystems. The invaders have established themselves as a dual threat to biodiversity and economies worldwide, and their unchecked proliferation is causing ripples across ecosystems and financial landscapes.

 At present, more than 37,000 alien species (plants, invertebrates, vertebrates, and microorganisms) have infiltrated ecosystems worldwide, with a staggering 200 new species being recorded annually. Among them, more than 3,500 are classified as invasive – impacting on biodiversity, ecosystem functioning, nature’s contribution to people and good quality of life. 

Invasive alien species are associated with a staggering 60% of recorded global extinctions (the majority on islands), and in 16% of cases, they are the sole driver of extinction. The effects of climate change can worsen their impact, reducing native species resilience to invasions and creating favorable climatic conditions for invasive alien species spreading. 

The financial impact of invasive alien species is equally concerning. The devastating effects of biological invasions extend beyond ecological damage and have a profound financial toll.  The estimated annual economic cost of biological invasions surpassed $423 billion in 2019. This cost includes both direct damage control and indirect economic consequences, particularly the reduction in food supply. 

Invasive alien species have been steadily increasing in number across all regions for centuries, and the economic costs associated with them have quadrupled every decade since 1970 on a global scale. Economic activities – such as international trade, transport, and utility infrastructure – can establish new invasion pathways, enabling their expansion, even reaching remote and ecologically pristine regions.

Invasive alien species contribute to marginalization and inequity, sometimes with gender and age-differentiated effects, disproportionately affecting those reliant on nature. Over 2,300 of the invasive species threaten lands inhabited by Indigenous Peoples. Local communities and marginalized groups are also significantly impacted by invasive alien vector-borne diseases. These biological invasions erode autonomy, cultural identities, and livelihoods by reducing mobility and land access. 

For example, the invasive apple snail, originally from Argentina and the northern Amazon basin, poses a significant threat to agriculture, particularly rice cultivation in Southeast Asian countries like the Philippines and Thailand. Introduced in 1980, it damages rice and taro crops, leading to reduced quality and yield, and promoting the spread of pathogens. In the Philippines alone, approximately 1.4 million hectares of rice fields have been infested, causing substantial economic losses for smallholder farmers and communities.

The battle against invasions will be pricey, but the cost of inaction will be even higher. The most cost-effective action is strengthening biosecurity protocols (pre-border and border screening, quarantine, surveillance, and rapid response). While it may be nearly impossible to eliminate the introduction of alien species, it is crucial to minimize their numbers to prevent the establishment of breeding invasive alien species populations. New technologies such as eDNA and AI can help to detect the most exposed pathways and can be useful to optimize the use of available funding.

The battle against invasions will be pricey, but the cost of inaction will be even higher

Eradication efforts have achieved some success, particularly with small, slowly spreading populations of invasive alien species, especially in isolated ecosystems. In the past century, 88% of eradication attempts on small islands have succeeded, particularly when targeting invasive alien vertebrates in Pacific islands. While large-scale eradications have also been accomplished, they may prove very expensive and sometimes can encounter socio-political adversities, especially when the target species are used as food sources for local communities.

Once invasive alien species are established, eradication is often impossible, so the focus shifts to control and mitigation. This involves using physical, chemical, or biological methods, or a combination. Physical and chemical controls work locally, but they can be costly and provide short-term relief only. Chemical methods may have unintended effects and require compliance with local regulations to avoid widespread contamination. 

Classical biological control uses natural enemies (biological agents) specific to invasive alien species to manage them. Mikania micrantha, a highly damaging fast-growing invasive plant from South America, affects agriculture and forests in Asia-Pacific, impacting especially rural communities. In its native region, a rust fungus effectively controls it. This fungus was introduced as a control agent in several Asia-Pacific countries with success. 

 The involvement of local communities in the fight against invasive alien species is important and, if adequately funded, can be a significant source of income and ensure the social acceptance of the program. 

Developing countries, with their growing economies, are at greater risk from invasive alien species, and they often lack adequate funds to manage this problem. However,  investing in invasive species management can prevent significant future losses and offer high economic returns.

Financial institutions can help identify and secure funding sources, including the new Global Biodiversity Framework Fund, which was created to support the CBD Kunming-Montreal Biodiversity Framework, including its Target 6 on invasive alien species. These funds can not only assist in invasive species control programs but also enhance governance by promoting coordination between countries, strengthening policies, and supporting research and new technology development.

Invasive alien species pose a significant development threat, but we are not powerless. By taking decisive action now, we can mitigate their impact, particularly on poor and vulnerable communities.