Urban areas as native habitat

Outline

• Why create native habitats in urban areas?

• Five principles to increase functioning native habitat & biodiversity

Why create urban habitats?

• Scientific – biodiversity hotspots at environmental cross-roads, under-protected and vulnerable

• Social – create sense of place (most people live in cities and have limited ‘wild’ exposure)

• Available resources – people and $• It’s practical, do-able, often fits in with other

uses and is more sustainable (resilient and cheaper in the medium term).

Why not? – we’re in NZ, it’s easy to increase natives in cities… especially mobile species

How are cities different?

• Flattened topography• High weed pressures• High disturbance

• Climate amplified• People but no grazing

‘Natural’ Ultic soils:old, famous

• Teeming humus layers and shallow, nutrient-supplying topsoils,

• Impoverished fertility• Structurally vulnerable;

clay sediment runoff • Undisturbed: no

surface casting fauna; low fire frequency

City soils

• Increased runoff & surface water flow: less infiltration, less storage, removal of watercourses, subsurface water flows cut

• Stressed plants: shallow rooting, less oxygen and water, warmer

damaged soil biota, mowing & removing leaves disrupts carbon cycling (N); elevated P (anti-myc), sometimes N

Five principles

• Tread gently – minimise impact & isolation• Bigger is often better – logs, area• Natives like natives - use native plants• Structurally complex, tall, dense is best• Plan for low maintenance & connectivity –

minimise disturbance, connect water and organic cycles for resilient systems

1

10

100

1000

0 1 2 3 4 5 6 7

Replicate

Infi

ltra

tio

n

(m

m/h

ou

r)

Wharewhaka Reserve gully

Wharewhaka footprint

Brentwood mid gully

Brentwood lower gully

2. Tread gentlyA. avoid, B. nurture, C.

rehabilitate

Bigger is often better

Patch size (least edge)

Canopy height

Coarse wood

Big patches – minimise edge

Big wood for insects.. food and hiding places

Big (untreated) wood for animals

Big wood for little plants – epiphytes, refuges, fungae

Big wood for erosion control

Big wood for erosion control

Structurally complex – tall & denseRichard Toft (Chch), Robin Gardner-Gee (Motuora)

0200

400600

8001000

12001400

1600

Nu

mb

er o

f n

ativ

e b

eetl

es

UnmanagedA

PlantedA

PastureB

Beetle assemblages in planted bush and unmanaged bush similar

Planted bush70 species

Pasture62 species

49

4

20

24

30

22

4

Unmanaged bush 96 species

Plan for low maintenance

• Let sleeping logs (and leaves) lie

• Weed removal at ground level (+ herbicide)

• Natural water flows and connectivity minimise need for irrigation and drainage

No dense, long-lived weedmat

How to heal soil

• Loosen – let air in

• Avoid traffic, especially when wet

• Maximise plant growth and cover (avoid direct rain drop contact – erosion)

• Use organic mulches

• Connect leaves and invertebrates to humus and soil

Control Litter removed Topsoil removed

Treatment

0

20

40

60

80

100

Tre

e vo

lum

e (%

of

con

tro

l)4 year-old trees15 year-old trees

Removing litter and topsoil reduces growth; soil recovers slowly

Plants need water & organic matter… so connect flows

What about exotics?

We have the colours

We have toughness

Principles

• Tread gently – minimise impact & isolation• Bigger is better – logs, area• Natives like natives • Structurally complex is best• Plan for low maintenance & connectivity

(water and leaf litter)

Fabulous free NZ resources

www.doc.nz/regional-info/010Canterbury/005Publications/Protecting-and-Restoring-Our-Natural-Heritage

www.bush.org.nz/planterguide

www.landcareresearch.co.nz • Hewitt 2004 ‘Soil Properties for plant growth’