Invasive species and the environmental and economic costs of global spread
Published on 23 August 2026 at 03:19 GMT
By Editorial Team SDG15
An alien species is an organism moved by human activity beyond its natural range. It becomes invasive when it establishes and spreads, causing negative impacts on nature and often on people. The distinction matters: many non-native species are useful or benign, and only a minority become invasive. The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) reported in 2023 that more than 37,000 established alien species had been recorded worldwide, of which more than 3,500 had documented negative impacts.
Those impacts are both environmental and economic. IPBES estimated that the global annual cost of biological invasions exceeded US$423 billion in 2019, with costs at least quadrupling in each decade since 1970. The estimate covers damage to nature's contributions to people and quality of life, as well as expenditure on management. It is not a complete global invoice: the assessment identified substantial gaps in documented costs across regions and ecosystems. IPBES attributed 92 per cent of documented invasion costs to damage and the remaining 8 per cent to management spending.
How global movement opens pathways
International trade carries organisms deliberately as crops, livestock, ornamental plants, pets and aquaculture species. It also moves them accidentally. Seeds, insects and plant diseases can travel with agricultural produce, nursery stock, soil and untreated wood. Organisms can hide in containers, pallets, vehicles and aircraft, while ships transport aquatic life in ballast water or on hulls. The Food and Agriculture Organization of the United Nations (FAO) notes that expanding trade, faster travel and new routes have increased the opportunities for introductions.
Transport networks then connect ports and airports to farms, rivers, forests and cities. Tourism adds further pathways through luggage, food, outdoor equipment, boats and the intentional movement of plants or animals. A species may arrive several times before one introduction establishes a population, so repeated movement can raise the chance of invasion even when each individual event appears minor.
Changing climatic conditions alter what happens after arrival. Warming, changed rainfall and extreme events can make new locations suitable, reduce the competitive advantage of native species or change the timing of reproduction and disease transmission. The Intergovernmental Panel on Climate Change (IPCC) assesses that invasive plants are projected to expand in latitude and altitude, while pests, weeds and diseases are expected to increase in occurrence and distribution as warming proceeds. Climate change does not transport an organism across an ocean by itself, but it can create conditions in which an introduced population is more likely to persist.
Losses across food systems and forests
On farms, invasive weeds compete with crops for water, light and nutrients. Insects and pathogens reduce yields, damage stored products, kill livestock or increase expenditure on surveillance and control. Quarantines and import restrictions can affect market access when a pest becomes established. These effects extend beyond farm accounts: lower output and higher production costs can affect food availability, prices and rural livelihoods. IPBES found that reduced food supply was the most frequently reported way in which invasive alien species affected people.
Fisheries and aquaculture face related pressures. Introduced predators can consume native fish and shellfish; competitors can displace commercially valuable stocks; parasites and diseases can spread through traded animals, escaped farm stock or contaminated equipment. Invasive aquatic plants and fouling organisms can obstruct waterways, nets and infrastructure. In the Mediterranean and Black Sea, the General Fisheries Commission for the Mediterranean (GFCM) reports that non-indigenous species can outcompete or prey on native species and introduce disease, although some arrivals also create new commercial opportunities. That mixed record complicates decisions where ecological harm and short-term income occur together.
Forests can be altered by invasive insects, fungi, plants and mammals. Tree mortality reduces timber value and can change shade, water cycles, soil conditions and fire behaviour. Roads, logging activity, nursery stock and wood packaging provide pathways into forest landscapes. FAO identifies further economic effects through reduced production efficiency, control costs, possible trade restrictions and losses in ecosystem services. Once a pathogen is dispersed through roots, spores or insect vectors across a forest, removal of every infected host may be impractical.
Native biodiversity bears lasting effects
Invasive species can prey on native animals that lack effective defences, compete for habitat and food, hybridise with related species, carry unfamiliar pathogens or transform fire and nutrient regimes. Islands are especially exposed because isolated species often evolved without the predators, competitors or diseases that arrive with human transport. IPBES found that invasive alien species had contributed, alone or with other drivers, to 60 per cent of recorded global plant and animal extinctions and were the sole driver in 16 per cent.
Damage can also make ecosystems more alike as a small group of successful invaders spreads between regions. The loss is not limited to species counts. Pollination, water regulation, soil formation, fisheries productivity and cultural relationships with landscapes can change as ecological communities are reorganised. This connection makes the issue relevant to SDG 15 (life on land), whose Target 15.8 addresses prevention of introductions and reduction of invasive species impacts.
Why action is cheaper before establishment
Prevention and early detection generally offer greater leverage because populations are smallest and geographically limited at the beginning of an invasion. Screening high-risk imports, applying plant and animal health rules, treating ballast water and wood packaging, cleaning equipment, monitoring likely entry points and sharing surveillance information all act on pathways or new incursions. The Convention on Biological Diversity (CBD) states that preventing introduction and establishment is more cost-effective than eradication after establishment.
When surveillance finds a new population quickly, a rapid response may still be able to remove it or contain its range. Delay changes the arithmetic. Reproduction creates more individuals, dispersal crosses property and administrative boundaries, and control has to continue across larger areas. Some methods can also harm non-target species or face public opposition, while inaccessible terrain and hidden life stages reduce the chance of complete eradication.
Established populations are not uniformly impossible to manage. Local eradication has succeeded in some settings, particularly on islands or where detection is reliable, and long-term control can reduce damage even when elimination is no longer feasible. The outcome depends on the species, ecosystem, invasion stage, available methods and sustained resources. The central economic contrast remains one of timing: preventing one arrival or responding to a small outbreak can avoid recurring losses and control expenditure that continue after an invader becomes part of the landscape.
Further information:
· Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, Summary for Policymakers of the Thematic Assessment Report on Invasive Alien Species and their Control (2023), supports the global figures on established and invasive alien species, economic costs, impacts and recorded extinctions. https://doi.org/10.5281/zenodo.7430692
· Convention on Biological Diversity, Kunming-Montreal Global Biodiversity Framework Target 6, explains introduction pathways and the cost advantage of prevention over eradication after establishment. https://www.cbd.int/gbf/targets/6
· Food and Agriculture Organization of the United Nations, Invasive species: impacts on forests and forestry, supports the analysis of trade, transport, tourism, climate and forest pathways. https://www.fao.org/forestry-fao/aliens/52519/en/
· General Fisheries Commission for the Mediterranean, Climate change and non-indigenous species, supports the account of ecological and commercial effects on fisheries. https://www.fao.org/gfcm/activities/environment/climatechange/en/
· Intergovernmental Panel on Climate Change, AR6 Working Group II technical summary, supports the assessment of climate-driven changes in invasive plants, pests, weeds and diseases. https://www.ipcc.ch/report/ar6/wg2/chapter/technical-summary/
