# Assessment of the ecological impacts of invasive alien plants in France using adapted EICAT and EICAT+ protocols

Thomas de Solan, Aurélien Caillon, Guillaume Fried, Yohann Soubeyran, Arnaud Albert

► To cite this version:

Thomas de Solan, Aurélien Caillon, Guillaume Fried, Yohann Soubeyran, Arnaud Albert. Assessment of the ecological impacts of invasive alien plants in France using adapted EICAT and EICAT+ protocols. 13th International Conference on Biological Invasions, Sep 2024, Lisbonne, Portugal. .
hal-04908600

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https://hal.science/hal-04908600v1

Submitted on 23 Jan 2025

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Distributed under a Creative Commons Attribution 4.0 International License
# Assessment of the ecological impacts of invasive alien plants in France using adapted EICAT and EICAT+ protocols

Thomas de Solan ¹, Aurélien Caillon ¹, Guillaume Fried ², Yohann Soubeyran ³, Arnaud Albert ⁴

1: Conservatoire botanique national Sud-Atlantique, Audenge, France ; 2: Agence nationale de sécurité sanitaire de l'alimentation, de l'environnement et du travail, Montferrier-sur-Lez, France ;

3 : Comité français de l'Union internationale pour la conservation de la nature, Montpellier, France ; 4 : Office français de la biodiversité, Nantes, France

## CONTEXT AND OBJECTIVES

The **development of prioritized checklists** ranking alien taxa according to their **risk to biodiversity** is an essential step towards **effective management** of invasive alien species. In France, such lists for alien plants are drawn up by different structures at regional and national scales using various risk assessment methods. This lack of homogeneity in assessment methods limits the implementation of the French national strategy on IAS.

To address this problem, **we investigated if two recent global frameworks, EICAT and EICAT+, have the potential to become standards for assessing the ecological impacts of alien plants in France.** These two frameworks are used to assess the negative and positive impacts of alien species, respectively.

### STUDY OBJECTIVES

1) Adapt EICAT and EICAT+ for an implementation at a national scale

2) Test the adapted methods on the main invasive alien plants of France

## MATERIALS AND METHODS

We found two main issues with the current protocols. First, they are intended to be based on bibliographic data only, that are lacking at small spatial scales. Secondly, their criteria are difficult to apply to plants in a continental context : the concept of a local population is difficult to define for continental native plants, and it is therefore difficult to assess a local extinction versus a decrease/increase of local population size.

To address these issues, we proposed several adjustments :

* We **included the field observations** of experts specialized in ecology as an additional source of information for impact data

* We chose to **assess impacts at the scale of the site**, and proposed a translation of field observations in the EICAT assessment. We could not provide a translation for EICAT+ as the positive impacts were mainly indirect and therefore difficult to assess with field observations

* Of the alien plants, we identified the ones that impacted : (i) **endangered species** and (ii) **habitat of Community interest**

We applied the adapted methods on **228 alien plants** that were considered as invasive in at least one French region.

<figure><img src="image_2.png" /></figure>

## RESULTS

<figure><img src="image_3.png" /><figcaption>**Impact categories** for the **EICAT** (left) and **EICAT+** (right) assessments of the 228 invasive alien plants in France</figcaption></figure>

* **Field observations are an important source of data** : taking field observations into account has reduced the number of Data Deficient species from 31% to 5%, and has helped to precise the assessments of species with bibliographic data.

* **Negative impacts are easier to assess than positive impacts** : fewer species are assigned in the Data Deficient categories (12 vs 84) and had a low confidence score (12 vs 84) in EICAT than EICAT+ assessments.

* **Negative and positive impacts do not concern the same species** : negative impacts mainly concern native plants, while positive impacts mainly concern native animals.

* **The comparison between EICAT and EICAT+ is biased** : the two methods don't take into account the number of native species, and the **negative impacts** of invasive alien plants **affect many more species than their positive impacts**.

* **Negative impacts seem nevertheless higher than positive impacts.**

## Translation of field observations in EICAT categories

### Minimal Concern

* No visible impact

<figure><img src="image_4.png" /></figure>

### Minor

* Plant well established but no large and dense stands

<figure><img src="image_5.png" /></figure>

### Moderate

* Plant forming dense stands (cov. >50%) over **10s to 100s of m2**

* Lower species abundance or richness in the stands

<figure><img src="image_6.png" /></figure>

### Major

* Plant forming dense stands (cov. >50%) over **1000s of m2**

* Lower species richness in the stands

* Impact repeated in time

<figure><img src="image_7.png" /></figure>

### Massive

* Plant forming dense stands (cov. >50%) over **1000s of m2**

* Lower species richness in the stands

* Impact repeated in time

* Known **long-term abiotic impact**

<figure><img src="image_8.png" /></figure>

## CONCLUSION

* The **negative and positive ecological impacts of 228 invasive alien plants** are now assessed at the scale of France.

* **EICAT and EICAT+** can be **applied at national scale if field observations and expert reviews are included.**

* Alien plants are well suited for an impact assessment based on field observations, because their negative impacts are very visual.

* **EICAT and EICAT+** should **not be used simultaneously to make hierarchical list and cannot be compared.**

<figure><img src="image_9.png" /></figure>