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Insects and Green Walls

Caroline Chiquet, John Dover, Paul Mitchell, Dave Skingsley, Roger Dennis

The Green Wall Centre, Staffordshire University, Stoke-on-Trent ST4 2DF, UK.

http://www.staffs.ac.uk/research/greenwall/

Types of Green Wall

CONTEXT

Very little had been published on insects on Green walls – especially in English

None on living walls

But insects are important – ecosystem services

In urban areas – may be the only habitat available or exploited

Mean abundance of pollinating insects

visiting ivy flowers (on hedges) in 18 x 0.5 m2

quadrats

(Jacobs et al. 2010).A problem?

River Walls and Embankments

River walls along the Thames estuary foreshore (Attrill et al. 1999)Hoggart et al. (2012) 15 vertical wall sites along Thames in London.

© John Dover

Not all insects on green walls have the same lifestyle

Hagedoorn & Zucchi (1989)

Phytophages

(Herbivores)© John Dover

Saprophages

(Detritus feeders)

Jokey images of bottom feeders removed

Saproxylic

(Dead wood eaters)

Image of Beaver eating tree removed to protect the innocent

Predators

(Predators)

Picture of scary Dinosaur removed for public safety

Parasites

(Parasites)

Horrible pictures of parasites removed for reasons of good taste

This study

Insects surveyed on:

•Green Façades•Living Walls•Green Screens

Green Façades

29 Green Façades compared with Bare Walls

Green Façades - Ivy

Species used:

H. helixH. colchicaH. iberica© John Dover

Green Façades – Boston Ivy

Parthenocissus tricuspidata

© John Dover

Green Façades – Virginia Creeper

Parthenocissus quinquefolia

© John Dover

Green Façades – Pyracanthus

© John Dover© John Dover

Green Façades – Wisteria

© John Dover

Green Façades – Jasmine

m2

© John Dover

© John Dover

Sampled• 29 Façades and bare walls• Summer and autumn• 3 times/season• 2-6 sites a day• Deciduous and evergreen• Single or multiple species

Vortis© John Dover

Locations: Newcastle-under-Lyme and Stoke-on-Trent

Compared

Total insect abundance and richness (all insects)

Abundance and richness of the Orders:• Coleoptera (beetles)• Diptera (flies)• Hemiptera (bugs)• Hymenoptera (bees and wasps)

Total Abundance

Bare walls: 124

Green Facades: 6404

Mostly:• Hymenoptera 1599• Diptera 1558 • Hemiptera 1324

0

200

400

600

800

1000

1200

Booklice Parasiticwasps

Leaf hopper Aphids Gall midges Parasiticwasps

Tota

l ab

un

dan

ceGreen Façades – most abundant families

Most numerous ‘Family’ members

Total Richness – Green façades

0

5

10

15

20

25

30

35

40

Overall Beetles Flies Bugs Bees. Etc

Mea

n n

um

ber

of

spec

ies

±SE Façades: 208 species

Bare walls: 2 species

0

6

12

Coleoptera Diptera Hemiptera Hymenoptera

mean insect abundance

Beetles Flies Bugs Bees & Wasps

12

6

Mea

n in

sect

ab

un

dan

ceSummer Autumn

0

2.5

5

Coleoptera Diptera Hemiptera Hymenoptera

mean insect richness

Beetles Flies Bugs Bees & Wasps

5.0

2.5

Mea

n in

sect

ric

hn

ess

Summer Autumn

0

10

20

30

40

50

Evergreen Deciduous

Abundance

0

2

4

6

8

10

12

14

Evergreen Deciduous

Richness

Deciduous & Evergreen foliage (overall)

0

6

12

Coleoptera Diptera Hemiptera Hymenoptera

mean insect abundance

12

6

Beetles Flies Bugs Bees & wasps

Mea

n a

bu

nd

ance

EvergreenDeciduous

Deciduous & Evergreen abundance

0

2

4

Coleoptera Diptera Hemiptera Hymenoptera

mean insect richness

4

2

Beetles Flies Bugs Bees & wasps

Mea

n r

ich

nes

s

EvergreenDeciduous

Deciduous & Evergreen richness

0

60

120

summer autumn

mean insect abundance

diverse species (other than Hedera spp.)

diverse species (Hedera spp.)

single species (not Hedera sp.)

single species (Hedera sp.)

Summer Autumn

120

60

Mea

n a

bu

nd

ance

Polyculture/Monoculture

0

10

20

mean insect richness

diverse species (other than Hedera spp.)

diverse species (Hedera spp.)

single species (not Hedera sp.)

single species (Hedera sp.)

Summer Autumn

20

10

Mea

n r

ich

nes

s

Polyculture/Monoculture

Living Walls

22 Living Walls from 6 manufacturers

Located: Greater London (13) and Birmingham (9)

+ 4 ‘Green Screens’ : Stoke-on-Trent (2), London (2)

© John Dover

ANS

Plastic modules, open vertically and slightly angled to hold growing media

© John Dover

Treebox

Easiwall system: Plastic modules, horizontally open at the top, angled front

http://www.alexandrafroggatt.com/treebox/

For pictures of this system see:

Biotecture

Grodan rockwool units with polypropylene surround and front

© John Dover

Mobilane

Hydrophobic rockwoolunits with embedded growing medium

© John Dover

© John Dover

Wallflore system*

http://wallflore.de/projecten/jean-paul-viguier.html

Rockwool units with geo-textile in front

* Supplied by Grange Construction & Roofing Company Ltd.

For pictures of this system see:

Treebox

www.alexandrafroggatt.com

Bin Fen system: plastic pots attached to a mesh

For pictures of this system see:

Mobilane Green Screens

© John Dover

© John Dover

Birmingham

Greater London

Sampling

• 22 living walls, 4 green screens• Sampled 4 times each• July to September 2012

• 2 days/session in London, 1 day in Birmingham

© John Dover

(i) Birmingham and London(ii) green wall systems (6 different living wall

systems and green screens) (iii) plant density and the plant richness (iv) vegetation surface area (v) aspect (vi) LW age(vii) pedestrian and vehicle traffic volumes

Compared

Results

1399 insects

9 Orders61 families 137 species

Diptera (533)Hemiptera (451) Hymenoptera (217)

0

5

10

15

20

25

Overall Beetles Flies Bugs Bees &wasps

Mea

n r

ich

nes

s ±

SETotal Richness – Living Walls

137 species

0

50

100

150

200

250

300

350

Aphids Moth flies Fungus gnats non-bitingmidges

Mea

n a

bu

nd

ance

±SE

Total abundance – Living Walls

1399 insects

Most numerous ‘Family’ members

360 individuals6 orders 37 families59 species

Green screens

0

5

10

15

20

25

30

Overall Beetles Flies Bugs Bees & wasps

Mea

n a

bu

nd

ance

±SE

Green screens – Total abundance

360 individuals

Birmingham vs London

13 angled plastic units: 8 B’ham, 5 London – No differences

Different LW systems

No differences in overall richness or abundance

0

25

50

green screen plant pot horizontal plant box rockwool unit withplastic fascia

rockwool unit with feltfascia

rockwool unit angled plasticmodule

mean insect abundance

2525

Green screen

Plant pot

Horizontal planters

Rockwool + plastic front

Rockwool + felt front

Rockwool + bare front

Angled plastic unit

50

25

Mea

n a

bu

nd

ance

±SE

Living Wall system comparisons - abundance

No significant differences

0

7

14

green screen plant pot horizontal plantbox

rockwool unit withplastic fascia

rockwool unit withfelt fascia

rockwool unit angled plasticmodule

mean insect specie

s r

ichness

Green screen

Plant pot

Horizontal planters

Rockwool + plastic front

Rockwool + felt front

Rockwool + bare front

Angled plastic unit

14

7

Mea

n r

ich

ne

ss ±

SELiving Wall system comparisons - Richness

No significant differences

BUT:

Dipteran abundance was significantly greater in horizontal plant boxes than on all the other systems (with the exception of plant pot systems)

AND significantly greater in abundance in plant pot systems than in angled plastic modules

Diptera (Flies)

Dipteran richness was significantly greater in horizontal plant boxes, plant pots and green screens than in angled plastic modules

Hemipteran abundance was significantly greater in rockwool units than in all the other systems (with the exception of green screens)

AND was significantly greater in angled plastic modules than in plant pots and horizontal plant boxes

Hemipteran richness was greater in rockwoolunits than in all the other systems) and was significantly greater in angled plastic modules than in plant pots.

Hemiptera (Bugs)

Ordination using multiple correspondence analysis (MCA)

• Green façades and living walls, have an abundant and diverse insect fauna

• Diptera, Hymenoptera, and Hemiptera were the most abundant and rich insect groups found

• Some pests were present

• Nearly all Hymenoptera were wasps or parasitoids(either primary or hyperparasitoid)

• Psocoptera (book lice) – consuming decaying material

Take-home messages

Take-home cont’d

Evergreen superior to deciduous

Accessibility of media surface and decaying material may be reason for high numbers of Diptera

Hemiptera may be positively affected by high foliage density

Not possible to say whether GF, LW are better than the other – they are diffierent

Thank you for your attention!

© John Dover