Invasions biologiques : quelles conséquences pour nos sociétés ?

Summary

Biological invasions can harm human societies as well as biodiversity and ecosystems. Although some invasive alien species may provide benefits, the video describes these as generally outweighed by negative effects, including health risks, reduced food supplies, infrastructure damage, economic losses, threats to livelihoods, and psychological stress.

The video draws on the IPBES classification of impacts, highlighting two areas especially relevant to people:

• Nature’s contributions to people: Effects such as reduced food availability and increased risks from fires, soil erosion, allergenic pollen, zoonotic diseases, and poisonings or envenomations.
• Quality of life: Effects on material and non-material needs, including food and fuel, health, security, economic and cultural activities, and social relations.

Examples

• Common ragweed: Its allergenic pollen can cause allergic rhinitis and worsen asthma. Millions of Europeans are affected each year.
• Water hyacinth: Dense surface growth can disrupt aquatic ecosystems and reduce tilapia populations, threatening fishing, food security, and livelihoods.
• Tiger mosquito: Its spread has made it a vector of diseases including dengue, chikungunya, and yellow fever.
• Brown tree snake: On Guam, it has damaged electrical infrastructure and caused short circuits.
• Fall armyworm: It attacks important crops such as corn, sorghum, and rice, putting food security at risk.
• Black rats and house mice: They can carry pathogens associated with leptospirosis, plague, and salmonellosis. They also damage stored food and other goods, contributing to hardship.

Measuring the Economic Costs

Because the impacts are diverse, they are difficult to compare consistently. The video presents economic cost as a common, tangible measure—not as a separate type of impact, but as a way to quantify different impacts. Estimates can include direct and indirect damage, as well as the costs of managing invasive species. It can also be difficult to determine who ultimately pays, since costs may fall on governments, businesses, insurers, or individuals.

The InvaCost research network developed a shared approach to compiling and analyzing these estimates. Its methodology involves:

• Collecting estimates from scientific and non-scientific publications in a public, continually expanding database.
• Standardizing and compiling estimates so they can be analyzed together.
• Assessing costs at different taxonomic, geographic, and societal scales.

The analysis cited in the video estimates that biological invasions cost about $1.738 trillion over the previous 50 years, with costs exceeding $163 billion in 2017—more than 20 times the combined budgets of the WHO and the UN for that year. Reported costs have increased roughly fourfold per decade. The video says this trend may reflect both intensifying human activities that facilitate invasions and increased research documenting their costs; it is difficult to separate their relative contributions.

These totals are considered substantial underestimates: many impacts are undocumented, not yet assessed, or difficult to express in monetary terms. Reported costs are also unevenly distributed across species groups and countries. For example, insects, mammals, and the United States account for a large share of recorded costs, partly because of the impacts involved, but also because research and reporting capacity is greater in some places and for some taxa. Economic estimates can raise awareness, but they cannot capture every consequence for societies and ecosystems.

Researchers and Sources Featured

• Christophe Diagne — IRD research scientist, identified in the video metadata.
• IPBES — Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services.
• InvaCost — Research network and database for documenting and analyzing the economic costs of biological invasions.