Impacts on Nature

Invasive alien species are one of the five most significant direct drivers of biodiversity loss, alongside land-use changes, direct exploitation of species, climate change, and pollution.

Invasive species affect native species through ecosystem alterations, interspecies competition, predation or herbivory. More than a quarter of documented impacts involve ecosystem changes, such as changes in soil and water properties. One significant negative impact of invasive species is biotic homogenization, which leads to communities worldwide becoming more similar, affecting ecosystem structure and functioning. Alien species can also act as vectors for diseases and parasites, to which native species may not be resistant or adapted. Their influence can even be observed at the genetic level, displacing native genes in cases of hybridization. The extent and types of impacts vary depending on the specific invasive species, ecosystems, and regions involved.

Invasive alien species can cause dramatic, and in some cases irreversible, changes to biodiversity and ecosystems, including local and global species extinctions. Globally, invasive species are the main factor in 60% of extinctions, and the sole factor in 16% of cases. At least 218 invasive species are responsible for over 1,200 local extinctions.

Native and endemic species on islands are particularly vulnerable, with alien plants outnumbering native plants by more than 25% on all islands. Invasive species are responsible for 90% of island species extinctions.

Impacts on People

The benefits some invasive species may offer to humans do not mitigate or eliminate their negative impacts. Invasive alien species significantly affect the economy, food and water security, human health, and quality of life.

Economic damage can occur directly, such as when a particular species multiplies and reduces crop yields, causes the disappearance of commercially exploited species or requires changes in management practices (more frequent mowing, more complex and frequent cleaning and repairs, etc.). Indirect costs arise from measures to prevent the spread of invasive alien species (treating materials, more frequent product inspections, etc.), population management or removal efforts.

In Slovenia, the most well-known invasive alien species that affect human health are common ragweed, giant hogweed and the tiger mosquito. The first causes allergies due to its pollen, the second causes burns, and the third is known for its irritating bites and its potential as a disease carrier. Other invasive species also pose health risks.

In Slovenia, two species, the giant hogweed and the tree of heaven, can be harmful to human health and their removal requires special caution and protective measures. The sap of giant hogweed is phototoxic; when it comes into contact with skin or mucous membranes and is then exposed to sunlight, it causes burns and slow-healing ulcers. Contact with the eyes can cause severe damage. The sap of the tree of heaven can cause allergic reactions and when it enters the body through wounds, blisters, or other skin injuries, it can cause myocarditis (inflammation of the heart muscle). Some invasive alien plants are also harmful due to their allergenic properties, including common ragweed, box elder, prickly cocklebur, cocklebur and annual wormwood. Ambrosia pollen, released during the flowering period, is highly allergenic, causing eye and nasal inflammation and even worsening asthma in humans. For allergy sufferers, touching the stems and leaves of these plants with bare hands can be harmful.

Global economic costs caused by invasive species exceeded €390 billion annually as of 2019, with the costs increasing fourfold each decade since 1970. The vast majority of costs (92%) arise from impacts on ecosystem services, the exploitation of natural resources, and the quality of human life, while only 8% is related to the management of invasive species.

How Many Invasive Species Are Known?

Throughout history, many alien species have been intentionally introduced for perceived human benefits, but the negative impacts of those that become invasive are enormous for both nature and people. There are numerous ways species can travel to new locations, either intentionally or unintentionally, through human activities, where they can establish and reproduce; these are referred to as pathways of introduction.

Today, human activities introduce alien species into all regions and ecosystems of the world at an unprecedented rate, contributing to the establishment of approximately 200 new alien species each year. Over 37,000 alien species have already been introduced globally due to human activity. Of these, more than 3,500 have documented negative impacts, making them classified as invasive alien species. In fact, 85% of biological invasions have negative impacts on native species. Approximately 1,061 (6%) alien plants, 1,852 (22%) alien invertebrates, 461 (14%) alien vertebrates, and 141 (11%) alien microorganisms are considered invasive species. Since 1970, the number of invasive alien species has increased by 37%. The majority of recorded impacts from invasive species occur in terrestrial ecosystems (75%), particularly in forests and agricultural lands, with freshwater ecosystems affected by 14% and marine ecosystems by 10%.

Predictions

The presence and impact of invasive alien species are rapidly increasing globally and are predicted to continue rising in the future. Even without the introduction of new alien species, already established species will continue to spread to new countries and regions. Biological invasions and the impacts of invasive species may be exacerbated or reinforced by indirect anthropogenic factors (demographic, economic, sociocultural, technological, and those related to institutions and governance) and natural factors (especially natural disasters such as floods, storms and fires), declines in biodiversity, and interactions between invasive species. If these trends are not altered, it is expected that by 2050, the number of invasive species will increase by 36% (compared to 2005).

Commitment to the Future

As part of the new Kunming-Montreal Global Biodiversity Framework, in December 2022, countries worldwide committed to reducing the introduction and establishment of priority invasive alien species by at least half by 2030. Achieving this ambitious goal will require a comprehensive approach to managing invasive alien species, tailored to the specific contexts and situations in different countries and sectors, and involving stakeholders across various areas (ensuring biosecurity, trade and transport, human and plant health, economic development, and other industries). Successfully fulfilling this commitment will have far-reaching benefits for both nature and people.

Adapted from:

• Roy, Helen, et al. “Summary for Policymakers of the Thematic Assessment Report on Invasive Alien Species and their Control.” IPBES Invasive Alien Species Assessment (2023): 1-56.

• Projekt LIFE ARTEMIS. Tujerodne vrste. https://www.tujerodne-vrste.info/tujerodne-vrste