Dynamic Dunes Congress 2015 Workshop: Grazing the dunes - Hubert Kivit

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!