Study Notes on the Impacts of Alien Species in Europe

Biological Invasions and Ecosystem Services

Biological invasions complicate the conservation of biodiversity and ecosystem integrity worldwide. The impacts of invasive species can threaten biological diversity in various ways:

  • Reduction of Genetic Variation: Invasive species can reduce genetic variation and erode gene pools.

  • Extinction of Endemic Species: The spread of invaders can lead to the extinction of endemic species.

  • Alteration of Habitat and Ecosystem Functioning: Invasive species can modify natural habitats and disrupt ecosystem functions (Hulme 2007).

In addition to ecological impacts, biological invasions also have economic ramifications that can be quantified as financial costs, which stem from the presence of high-profile alien pests (Pimentel et al. 2001, 2005; Born et al. 2005; Colautti et al. 2006; Olson 2006; Lovell et al. 2006). However, there's a notable gap in the comparison of ecological and economic impacts across geographic regions or taxonomic groups—essential for prioritizing management actions. The socioeconomic consequences of biological invasions are subtle and challenging to evaluate using traditional monetary methods and market-based models (Binimelis et al. 2007).

To address these complexities, ecological and economic impacts were analyzed using the Millennium Ecosystem Assessment framework (MA 2005), linking ecological changes to ecosystem services and, consequently, to human well-being. This approach classifies ecosystem services into four primary categories:

  1. Supporting Services: Basic ecosystem resources and energy cycles.

  2. Provisioning Services: Production of goods (e.g., food, fiber, fresh water).

  3. Regulating Services: Maintenance of ecosystem processes.

  4. Cultural Services: Non-material benefits such as recreation and aesthetic enjoyment.

DAISIE Project Overview

Recent comprehensive data from the DAISIE (Delivering Alien Invasive Species Inventories for Europe) project have paved the way for the first pan-European assessment of the impacts of alien species—plants, vertebrates, and invertebrates—across terrestrial, freshwater, and marine systems. Key findings include:

  • Number of Species: Over 10,000 species alien to Europe were registered, of which:

    • 1094 species have documented ecological impacts (about 11% of alien species).

    • 1347 species have documented economic impacts (around 13%).

  • Major Impacts: Terrestrial invertebrates and terrestrial plants are the taxonomic groups with the most species causing impacts. The North Sea experiences the most significant ecological and economic impacts.

  • Correlations: There is a high correlation between ecological and economic impacts across taxa and regions. Specifically, terrestrial invertebrates tend to cause greater economic impacts compared to ecological impacts, while the opposite is true for terrestrial plants. Alien species from all taxonomic groups affect the four categories of ecosystem services and impact human well-being.

General Trends in Ecological and Economic Impacts

  • The most extensively documented alien species include terrestrial vertebrates and terrestrial invertebrates. Species such as the muskrat (Ondatra zibethicus) and the raccoon dog (Nyctereutes procyonoides) are known for causing problems across many European regions.

  • Plant species often do not have widespread ecological impacts, with some highly invasive species being localized (e.g., tree of heaven (Ailanthus altissima) and Japanese knotweed (Fallopia japonica)).

  • Numerical Analysis: Reports indicate more species cause economic disasters than ecological ones because of stakeholders' greater awareness of economic impacts.

Types of Ecosystem Services Affected by Invasive Species

Using the classification of invasive species according to the types of impacts they have on ecosystem services:

  • Supporting Services: Modification of soil, alteration of nutrient cycling, community changes, etc.

  • Provisioning Services: Loss/gain in food sources, threats to endemic species.

  • Regulating Services: Alteration of biological control, changes in pollination.

  • Cultural Services: Changes in recreational use, aesthetics, etc.

For instance, species like the American crayfish (Procambarus clarkii) are reported to affect food webs significantly due to their foraging habits, leading to cascading effects on native species.

Financial Costs of Invasive Species

Invasive species incur substantial direct costs predominantly through management expenditures such as eradication and control. Specific examples include:

  • The Coypu has caused agricultural damage while incurring management costs estimated in millions.

  • Crop losses due to invasive arthropods in the UK amount to approximately €3800 million annually (Pimentel et al. 2001).

  • For instance, the control of Heracleum mantegazzianum (giant hogweed) costs significant amounts throughout temperate Europe.

Although only a fraction of invasive species' economic impacts are comprehensively evaluated, there is an urgent need for more detailed data across Europe to develop effective management strategies.