Download Urban areas as native habitat

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, nutrientsupplying 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
2. Tread gently
A. avoid, B. nurture, C.
rehabilitate
Infiltration (mm/hour)
1000
100
Wharewhaka Reserve gully
Wharewhaka footprint
Brentwood mid gully
Brentwood lower gully
10
1
0
1
2
3
4
5
6
7
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 & dense
Number of native beetles
Richard Toft (Chch), Robin Gardner-Gee (Motuora)
1600
1400
1200
1000
800
600
400
200
0
Unmanaged
A
Planted
A
Pasture
B
Beetle assemblages in planted bush and
unmanaged bush similar
Unmanaged
bush
96 species
20
49
22
24
4
4
30
Pasture
62 species
Planted bush
70 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
Removing litter and topsoil reduces growth; soil recovers slowly
100
Tree volume (% of control)
4 year-old trees
15 year-old trees
80
60
40
20
0
Control
Litter removed
Treatment
Topsoil removed
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/regionalinfo/010Canterbury/005Publications/
Protecting-and-Restoring-Our-Natural-Heritage
www.bush.org.nz/planterguide
www.landcareresearch.co.nz
• Hewitt 2004 ‘Soil Properties for plant growth’