Urban areas as native habitat
Dec 15, 2015
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’