The choice of indicators

The inventories are carried out by points located a priori on map and then relocated during the first field visit, according to the accessibility and homogeneity of the habitat. The LIFE monitoring strategy is to target a broad spectrum of organisms associated with open intraforestry and edge habitats (vascular plants, birds, bats, butterflies), and ponds (Odonata and Amphibians).

Actions concerned by the monitoring of biological indicators

Among the 7 actions of the LIFE project, two of them (orchards and invasive plants) can not be the subject of a multi-group monitoring of the evolution of biodiversity. The quickness of response of biological indicators to the actions carried out varies considerably: the reaction to the digging of a new pool is almost immediate, whereas the development of the planted edges will take 10 to 15 years before expecting an effect on the organisms associated with it.
Consequently, the process of measuring the biological diversity of an initial state and subsequently adjusting and measuring its effects is rather relevant only to the created ponds or to certain developments made at the beginning of LIFE (flowery meadows, vegetation to restore moors). Typically, the monitoring of the planted edges will not make it possible to evaluate the beneficial effect of this action over the duration of the project.
On the other hand, the overall analysis of the inventories will make it possible to constitute a unique overview of the situation for the high tension transmission network on a broad spectrum of biological groups in the wooded areas of the Walloon Region.

Two ways of collecting biological data under high voltage lines are summarized in this document:
1. Standardized inventories: fixed points performed according to a precise method, repeatable elsewhere and throughout time.
2. Collection of all opportunistic data: allows to complete the overview of local fauna (and flora) and supplements the standardized inventories.

The motivation for selecting the inventorized groups is illustrated in the following table and diagram.

Schematic representation of the relevance of the groups studied in the different compartments of the studied habitats: forests, edges, grasslands and ponds. The thickness of the lines indicates the relevance of the study of these groups according to the habitat in which they are located in the corridor.

Table 1: taxonomic groups studied in the project. A cross indicates the relevance of these groups to the different actions.

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Birds

Introduction

The bird inventorization protocol set up under the LIFE Elia project is largely inspired by the birdwatch protocol established by the monitoring program for common birds (SOCWAL). This program has been active in Wallonia since 1990. The system is based on the detection of territorial manifestations, it makes it possible to highlight trends in the populations of bird species known as “widespread” or with “fairly numerous” numbers.

Morning breeding bird inventory

Results

Average number of individuals per inventorization point for each area

Click on the column headings to sort the values, click on a line to mark it

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Bird density per point

During the surveys, 56 bird species were identified.

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Butterflies (Rhopalocera)

During the drafting of the project, the aim was to target 15 zones to be inventoried each via 5 permanent inventory points. It quickly became clear to us that this goal had to be slightly revised downwards, for various reasons, foreseeable or not: * In order to minimize geographical redundancies, the points are placed about 500 m apart. LIFE sections of less than 2.5 km in length can therefore not contain the desired 5 points.
* The ease of traveling under certain lines has sometimes been undervalued, which significantly increases the time it takes to travel in a single area, up to a full day in the most extreme cases.
* The geographical spread of the sites on the Walloon Region imposes significant travel times between the sites, making it impossible for an observer to survey more than 2 sites on the same day.

The total number of butterfly inventory points sums up to 58, with 13 tested in 2012 but not repeated later since they were too inaccessible or time-consuming for the team to perform.
The remaining points and subsequently inventorized are localized in the following map. The data are later comprehensively presented as table with regard to the Walloon Region’s Red List.

Handling a butterfly in the field for identification and for taking picture validating this data

Number of species

Number of species per LIFE zone (standardized inventories)

LIFE zone	Number of species
Zone 06: Marche-en-Famenne	37
Zone 01: Couvin	36
Zone 10: Florenville	36
Zone 13: Spa	32
Zone 07: Nassogne-Tenneville	27
Zone 15: Arlon	27
Zone 02: Doische	26
Zone 12: Durbuy	26
Zone 04: Anhée	25
Zone 09: Bertrix-Neufchâteau	17
Zone 14: Vielsalm	15

Commonness of butterflies (as number of inventorised point with the presence of a species).

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Dragonflies and damesflies (Odonata)

The objective of performing inventories on 20 ponds was quickly reached and will be outnumbered since 51 ponds were already visited to date. Although, it will be more pertinent to consider data as a whole for a group of close ponds, given the very high mobility of dragonflies. Inventories began when ponds were created for at least one year.

A damesfly (Enallagma cyathigerum)

Amphibians (Anura & Urodela)

The objective of carrying out inventories on 20 ponds was achieved in 2016. To date 29 ponds have been inventoried. Inventories began when ponds were created for at least one year and will were repeated in the third year of their natural evolution.

A few knewts at the bottom of one of the metal traps used for inventories

Reptiles (Lizards, slowworm and snakes)

Reptiles are likely to occur in all habitats fitted out and managed by LIFE, among which are the edges (Action C1) and habitats of high biological value (Action C3) in particular. The forest edges well exposed to the sun, moors and peat bogs are habitats already too rarefied in the Walloon region and yet they are indispensable refuges to the populations of our three species of snakes.
These habitats associated with local features such as ponds and other water outfittings or the realization of hibernacula should be all the more favorable to snakes.

Counting of reptiles which shelter under the plates placed on the ground

Higher plants

The main objective of the botanical description is to establish an inventory of the structure and plant composition in the forest corridors of the high voltage lines. Apart from the special cases of ponds and the removal of invasive plants, the effects of LIFE will be difficult to assess on a short time scale imposed by the duration of the LIFE Elia project.
We have opted for a transect description allowing the standardized description of habitat gradients from the herbaceous to tree strata. A transect is performed starting from the axis of the power line to the forest, in which a phytosociological inventory is carried out over a width of 5 m in each of the 3 elements present: herbaceous layer, shrubs and tree layer (including 5 first meters of the forest). A second transect is then made close to the opposite half of the corridor to account for the effect of exposure (see diagram below).

Arrangement of a pair of transects in a homogeneous zone of 50 m. Depending on the extent of the LIFE site, the observer continues to progress to a new representative habitat.