Do ecoducts contribute to the coherence of Veluwe

habitats?

G.J. Brandjes, D. Emond, D. Wansink and G.F.J. Smit

The Veluwe is the largest non-aquatic Natura 2000 site in the Netherlands, 91.200 ha of forest and heathland. Natura 2000

91.200 ha

Natura 2000 91.200 ha

The Veluwe is highly fragmented by a dense network of local and regional roads and highways.

The dense traffic network act as barriers for terrestrial species. For species with wide home ranges as badgers, marten, deer highways are strict barriers, were regional roads are risk factors and prevent frequent migration. Habitat fragments are connected for these species, when not separaten by highways.

Network Theory

Nodes Edges

The clusters of Veluwe habitat can be presented as nodes and edges, as applied in network theory.

Network Theory

Nodes Edges

- habitat patches - weighed by surface

- weighed by connectivity

- local roads - regional roads - highways/motorways

Increasing traffic

Decreasing connectivity

The edges, connections between patches separated by roads, can be weighed by traffic density. The more traffic, the stronger the barrier, the lower its connection.

Network Theory

Nodes Edges

- habitat patches - weighed by surface

- weighed by connectivity

- ecoducts - stubb walls - fauna strips - fauna-, badger tunnels

Decreasing species #

Decreasing connectivity

Fauna passageway facilitate connectivity and can also be weighed accoording to number of species and frequency of usage.

Network Theory

Nodes Edges

PC index Probability of Connectivity

Saura and Hortal 2007

Saura and Hortal introduced PC, a promising index to evaluate changes in habitat networks.

Do ecoducts function?

20 patches 14 connections 8 clusters

Node/Patch Weighed

Edge/Connection Unweighed Undirected Ecoduct

Ecoduct New

Three ecoducts exist more than a decade, 6 are newly constructed.

• Camera traps • Sand and ink pads to register

tracks • Cover boards • Live traps and pit falls • Malaise traps for flying insects • Transects for visual counting

Survey techniques

Example of a fieldwork set up with multiple camera traps and cover board transects.

Some ecoducts have ponds. In most situations ponds are located sideways of the construction.

Camera traps frequently record deer, pig, fox and other species ...

Camera traps frequently record deer, pig, fox and other species ...

Tracks are registered from amphibians and small mammals.

Do ecoducts function?

• Used by multiple species groups • Species of surrounding habitats • Multiple species in first year after construction • Use is regular to frequent

Ecoducts are small habitat patches, visited by species, crossed by species and inhabited by species...

20 patches 14 connections 8 clusters PC-index 0.21

20 patches 20 connections 2 clusters PC-index 0.25

Do ecoducts function?

Ecoducts decrease the barrier function of highways and so contribute to Connectivity of the Veluwe network. PC index will increase, but for quantifying the network parameters, the Connectivity of roads and ecoducts should be properly quantified.

Do ecoducts contribute to the coherence of Veluwe

habitats?

• Ecoducts facilitate movements over highways • Ecoducts establish connectivity between

habitats

For a wide range of species:

To quantify the contribution of ecoducts to habitat networks,

the application of Network Theory should be further developed

Do ecoducts contribute to the coherence of Veluwe

habitats?