Grazing has varying effects on the fauna of grey dune ecosystems. Studies found that grazing decreased the biomass and litter of vegetation, while having mixed effects on grasses and no effect on herbs. Grazing reduced food sources for insects and soil fauna like earthworms and millipedes, but increased flower abundance slightly under some grazing pressures. Grazing also reduced nesting habitats for sand-dwelling insects and altered habitat for some breeding bird species. The effects of grazing on thermoregulation and animal populations were mixed or insignificant. In conclusion, the impact of grazing depends on species, grazing intensity, and dune zone.

1. Grazing:
What about the fauna?
What do we learn from recent ‘Living Dunes’ (LD) & OBN research?

2. Methods
• OBN: 24 dune areas
– 113 locations with paired plots
(grazed-ungrazed)
• LD: 3 dune areas drinking water
companies

3. Studied effects of grazing on animals
• food
– soil fauna
– butterflies
– plant quality for insects and rabbits
– flower abundance
– invertebrates as food (for e.g. birds)
• nesting
– sand nesting insects
– habitat for breeding birds
• thermoregulation
– insects
– sand lizard

4. Main effects of grazing on vegetation
of grey dunes
biomass standing crop decreases litter decreases
grasses decrease herbs unchanged

5. Food: soil fauna
• Strong decrease of detritivores (earth worms, millipedes, wood lice)
• Contradictory results for herbivores & carnivores
• NHD: increase in detritivores (LD) !

6. Food: butterflies Year
round
horse +
cattle
Summer
cattle
other
Pyrgus malvae --
Coenonympha
pamphilus
-- --
Issoria lathonia ++
Maniola jurtina ++ ++ ++
Argynnis niobe ++ ++ ++
Lycaena phleas ++ ++ ++
Anthocharis
cardamines
--
Thymelicus lineola -- --
Pararge aegeria ++
Ochlodes faunus -- -- --
Favonius quercus ++
Aglais urticae -- -- --
Aphantopus
hyperantus
-- -- --
Many species show no effects
++ species of meagre vegetation or
small-leaved grasses
-- species of rough vegetation or
broad-leaved grasses
Effects partly caused by direct grazing
on host plants

7. Food: plant quality for insects and rabbits
Positive!

8. Food: plant quality for insects and rabbits
No better plant quality!

9. Food: flower abundance
Grazing increases flower abundance in R slightly
High grazing pressure in W decreases flower abundance

10. Food: soil invertebrates as food
• Density decrease of all size classes under grazing
• Effect stronger at high grazing pressure
• NHD: increase soil invertebrates (LD) !
Size class Significance
Renodunal Wadden
> 1.5 cm negative n.s.
0.5 – 1.5 cm negative negative
< 0.5 cm negative negative

11. Nesting: sand nesting insects
75% reduction of nests in grazed sand
patches
more thermophilous insects on
terracettes than on ungrazed slopes

12. Nesting: habitat alteration for breeding birds
Positive Neutral Negative
Open dunes 0 5 3
Low shrub 4 1 4
High shrub 1 4 9

13. Thermoregulation: insects
Larger differentiation in microclimate
in W at high grazing pressure decrease of
microclimate diversity

14. thermoregulation: sand lizard
• Contrary to inland situation
no effects of grazing on
trend in numbers

15. Conclusions
Effect of
grazing
Soil fauna abundance --?
Thermophilous
invertebrates
++/-
Nectar & pollen 0
birds --
Rabbits ++
Butterflies +
Sand lizard 0
Effects of grazing on fauna highly
dependent on
• species/species group
• grazing conditions
• dune zone
Much is still unknown!

16. Statement
in a dynamic dune system grazing by livestock
needs to be dynamic as well!