- people, deforestation and other...
TRANSCRIPT
22/12/2017
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Weeds, wildlife and forest restoration:
Queensland Weed Symposium, December 2017
Environmental Futures Research Institute
Carla Catterall
rethinking non-native species as enemies or allies
for Anthropocene biodiversity
The problem of Anthropocene
environmental degradation
- people, deforestation and other changes
Early European deforestation
strangler fig at Fig Tree Pocket
“...... I split the rock; I felled the tree: The nation was- Because of me!” Old Botany Bay- Mary Gilmore
Post-1945: more mechanised deforestation technologies
Joh Bjelke-Petersen Qld Premier 1968-87
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Chemical conditions (fertiliser, herbicide,
pesticide)
Other large-scale human-induced environmental changes:
Water availability (dams, drainage,
irrigation)
Plus – emerging climate change
Land topography (earth moving)
New species imported & grown (pasture grasses, others)
Net consequences:
new environments appearing
Former species are being removed
& the new environments may not suit them anyway
Old environments are destroyed; extinctions, biodiversity decline,
ecosystem degradation
New species are brought in by people;
the new environments will suit some of the new species
species invasions
.... all with largely unknown outcomes
?
“Novel ecosystems” are increasingly prevalent, defined by:
- driven directly or indirectly by human actions
- incorporation of new species, in new combinations
Reforestation is urgently needed
- if all remaining forests are protected
there will still be more ecosystem degradation and biodiversity decline
- because of time-lags in ecological outcomes
reforestation is needed, over large areas
simply to conserve what we have now
........ and even more to reverse declines
Ideas about aliens and natives
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Alien invasion is a changing idea
many introductions of plants and animals from “home”
2. When most Australians still were British .... 1800s – mid 1900s
transform countryside to a “superior” European appearance
e.g. through the Acclimatisation Societies
- alien species were admired and desired
3. Now we are true “Aussies”
people try to remove them from the environment
Alien species are disliked and vilified (except in agriculture and homes)
- adapted “native” and “alien” from common law
1. Early British botanists.... 1840s
transferred to define a ‘true’ British flora
concept of “a person born in another country”
BUT might semantic associations make us unduly biased?
eg adversarial and military metaphors - invasive species are enemies :
See blog: http://julianagyeman.com/2011/03/people-plants-and-racism/
“ferocious, fast growing foreign plants”,
“brutalise the native flora”
“ruthlessly ousting the natives”,
“encroaching foreigners”,
“pink and green Japanese terror”
“war on weeds”
Is the native vs alien division a useful guiding principle for forest restoration?
no
no
yes
yes
Benefit
Harm (dysfunction)
(e.g. diversity maintenance)
Native Alien = non-native
Species origin:
Ec
olo
gic
al fu
nc
tio
n:
- often “weed removal” is equated with environmental “restoration”
or on their ecological roles?
Should we judge species based on their origins?
?
? yes
yes
Benefit
Harm (dysfunction)
(e.g. diversity maintenance)
Native Alien = non-native
Species origin:
Ec
olo
gic
al fu
nc
tio
n:
yes or no?
non-native plants as pioneers in restoration ?
Is the native vs alien division a useful guiding principle for forest restoration?
What can the evidence tell us?
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Forest restoration processes
- the case of Australian rainforest landscapes
The main product of deforestation has been livestock pasture
2. Competition with seedlings - from grasses and herbs (usually non-native pasture grasses from Africa or S. America)
But even if livestock are removed, pasture often limits rainforest regeneration
1. Limited seed supply of forest tree/shrub species (seeds are typically short lived and need to be imported
- by fruit-eating fauna, mainly birds)
Catterall 2016. Biotropica
3. Predation of seedlings – by grazing animals (often native browsers, such as wallabies)
- because of ecological barriers:
pasture 7+ years since destocking
– Atherton Tableland
Overcoming the ecological barriers
Seed source (supply)
Seed survival & germination
Seedling survival & growth
Ecological barriers:
- most barriers can be removed by planting young saplings into suppressed pasture
Approach 1. Full replacement
- if at high density and high indigenous diversity
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eg, vegetation development in "good practice" restoration planting – Wet Tropics
8 yr 16 yr 22 yr
2 yr <1 yr
5 yr
Open canopy <70%
Closed canopy >70%
Overcoming the ecological barriers
Seed source (supply)
Seed survival & germination
Seedling survival & growth
Ecological barriers:
less costly
Approach 2. Use self-organised regrowth
but is it too slow?
.. and what if it is full of non-native plants?
The first trees to establish in disused pasture are often non-native species
e.g. common non-native pioneers of disused pasture
in Australian rainforest landscapes:
All typically considered weeds,
to be eradicated or suppressed
Camphor laurel Lantana
Privets
Wild
tobacco
= emerging dilemmas with non-native species
But is this always a useful approach?
Case study 1 – camphor laurel regrowth
Location: the “Big Scrub” Lismore region, northern NSW
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1958
View from Johnson Rd Eltham, c. 1950s
Example – Big Scrub, originally 750 km2 rainforest
1958: 0.1% forest; 99.9% cleared
(mostly dairy pasture)
1850: about 100% forested
1958
Example – Big Scrub, originally 750 km2 rainforest
1958: 0.1% forest; 99.9% cleared (dairy pasture)
1850: about 100% forested
2004
2004: 25% of the landscape was forest regrowth
photos courtesy W. Neilan
2004 1958
Camphor-dominated regrowth
1958: 0.1% forest; 99.9% cleared (mostly dairy pasture)
- BUT dominated by non-native camphor laurel, from China
2004: 25% of the landscape was forest regrowth
Example – Big Scrub, originally 750 km2 rainforest
1850: about 100% forested
photos courtesy W. Neilan
Understorey of established camphor
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Competing attitudes to camphor laurel:
1. undesirable invasive weed eradicate or suppress?
2. desirable habitat for threatened birds and catalyst of rainforest restoration tolerate or actively manage?
- OR
Neilan et al. 2006 Biol. Cons.; Kanowski et al. 2008 Ecol. Manag. Restn.
2. Rainforest regenerating under camphor trees?
Research to clarify its ecological role:
1. Used by frugivorous birds?
Survey of plants & frugivorous birds in 24 camphor patches >3 ha (survey sites 0.6 ha)
Yes, 34 species; 10 high quality seed-dispersers
Native tree species are:
25% of adult trees; but
47% of recruits (< 2.5 cm dbh)
Neilan et al. 2006 Biol. Cons.; Kanowski et al. 2008 Ecol. Manag. Restn.
ie Camphor is functioning as a catalyst of regeneration.
Camphor laurel Cinnamomum camphora
- fast grower,
- fleshy fruits widely dispersed by birds,
- tolerates drought/frost,
- not much browsed by wallabies.
- ecological properties
Establishes and grows well in pasture if not heavily grazed
Also:
- seeds short-lived,
- seedlings shade-intolerant
does not recruit well in dense regrowth or invade mature forest
Multiple ecological benefits of camphor regrowth
Evidence-based:
1. Increased diversity of native rainforest spp.
2. Improved native soil seed bank
3. Improved soil function
(nitrification, plant-available ammonium, phosphate)
2004
1958
Arguably likely:
4. Improved soil stability (slopes & streambanks)
5. Habitat linkages and stepping stones
6. Buffer for very small rainforest remnants (shade, microclimate)
7. Sequestered carbon
8. An overall decrease in other non-native
plant species.
Neilan et al. 2006 Biological Conservation; Kanowski et al. 2008 Ecol. Mgment & Restn.; Paul et al. 2010
For. Ecol. Mgment; Paul et al. 2012 Ecol. Mgment & Restn; Byron Shire Conservation Strategy 2004
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1. increases in introduced plants
2. declines in native rainforest plants (& threatened spp)
- due to loss of native plants within camphor patches
3. reduced soil function and soil stability
4. declines in native fauna - due to habitat loss & disruption of linkages
5. loss of buffer for very small rainforest remnants
further weed invasion, greater edge effects
6. less sequestered carbon
Ecological impacts of clearfelling camphor regrowth & converting to pasture
& 7. loss of several decades of accumulated regeneration potential.
No
. o
f s
pe
cie
s
No
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f s
pe
cie
s
In established camphor stands, treatment can accelerate native tree regeneration
Kanowski et al. 2008 Ecol. Manag. Restn.
Camphor regrowth
20-40 yr old
Old growth forest
Later successional tree species
Untreated camphor regrowth
1-5 6-12 Years since
camphor killed
3 years after treatment
6 years after treatment
Early successional tree species
Case study 2 – native vs non-native species in
replanted vs regrowth sites
Location: upland Wet Tropics, Atherton Tableland, north Queensland
Regrowth following dairy industry decline – Wet Tropics
1952
2011
1 km Tarzali, Atherton Tablelands
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Vegetation surveys in regrowth vs replanted sites of differing age
Replanted 15 yr
Regrowth 18 yr
1. Tree stem density (>2.5 cm dbh)
Shoo et al. 2016. Conservation Biology; Catterall 2016 Biotropica
Regrowth sites (27), 1-70 yr old
Replanted sites (24), 2-25 yr old
Vegetation surveys in regrowth vs replanted sites of differing age
Regrowth sites (27), 1-70 yr old
Replanted sites (24), 2-25 yr old
Over time:
- non-native spp often dominant, but then natives increase;
- native-only restoration plantings gain non-native species.
Non-native Lantana dying back in shade
Regrowth 65 yr
2. % of trees that are native species
Shoo et al. 2016. Conservation Biology; Catterall 2016 Biotropica
Rainforest
reference sites (N=8 sites)
Planted stems
in replanted sites (age 5-24 yr;
N=21 sites)
Recruited stems
in replanted sites (age 5-24 yr;
N=21 sites)
Restoration planting creates novel ecosystems
Pasture sites (N=5 sites)
- no trees
(Australian Wet Tropics)
Relative abundances of common tree/shrub species (@ >1 m tall)
the 10 most dominant in each context 28 species; from 540 in all)
Catterall et al. unpub.
Pro
pn
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tem
s top 10 in
forest
Pro
pn
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tem
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Pro
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non-native species
Case study 3 – kickstarting forest recovery
in retired pasture
Location: upland Wet Tropics, Atherton Tableland, north Queensland
..... experimental treatments
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Kickstart experiments
= kill grass & attract seed-disperser birds; no planting Grass suppression Bird perches
Start point = retired pasture with negligible tree regeneration after 7 yr
3 sites each 80 X 80 m
AthertonTablelands
Crassicaphalus sp
Non-native herbs
Polyscias sp
Native rainforest tree seedlings
Non-native shrub Solanum mauritianum
(wild tobacco)
CloudlandE
After 9 months
After 2 months
Kickstart sites – early recruitment – native tree seedling densities
Elgar et al. 2014. Frontiers in Plant Science
X 50 - herbicide
only
1 = untreated
grass
X 1500 - herbicide beneath pre-existing small trees - whether native or non-native
X 800 - herbicide beneath perches
Bird perches
Survival rates of planted seedlings
0
20
40
60
80
100
0 4 8 12 16 20 24 28 32 Weeks since planting
% o
f p
lan
ted
se
ed
lin
gs
wit
h liv
e l
ea
ve
s r
em
ain
ing
2X2 m plots 9 planted seedlings/plot N = 5 plots/treatment (5-70 m from forest edge)
Kickstart sites – limitations to recruitment success
Natural recruit
Bleeding heart Homalanthus sp (Euphorbiaceae)
Common pioneer tree
Catterall et al. unpub.
Tobacco overstorey
killed
Fenced & tobacco killed
Seedlings browsed
Pademelon Thylogale sp
Kickstart sites – after c. 4 years
Wild tobacco
Native trees
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non-native woody trees and shrubs CAN help to catalyse native
rainforest regrowth
From all 3 case studies - take-home message:
yes
yes
Benefit
Harm (dysfunction)
(e.g. diversity maintenance)
Native Alien = non-native
Species origin:
Ec
olo
gic
al fu
nc
tio
n:
yes
non-native plants as pioneers in restoration
Is the native vs alien division a useful guiding principle for forest restoration?
What the evidence tells us:
yes or no?
vine overgrowth
Case 4: vine choking in disturbed forest
Can be natives such as Cissus species Parsonsia species Elaeagnus species
- as well as non-natives yes
yes
Benefit
Harm (dysfunction)
(e.g. diversity maintenance)
Native Alien = non-native
Species origin:
Ec
olo
gic
al fu
nc
tio
n:
yes
non-native plants as pioneers in restoration
Is the native vs alien division a useful guiding principle for forest restoration?
What the evidence tells us:
yes
Overgrowth by native vines
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12
Conclusions
Species need to be judged and managed according
to their ecological roles,
not their origins
target interventions at species accordingly
- ecological benefit / harm balance
- area reforested per $ invested - to maximise:
Author’s note
Specific published information sources as shown within relevant slides are listed below.
This is a slightly modified version of the presentation to the Queensland Weed Symposium, Port Douglas, December 2017
In other cases, information herein should be used as a general guide to knowledge and ideas in this field; this presentation is not intended for use as a supporting reference in any written document.
Carla Catterall Acknowledgements:
• John Kanowski
• Kylie Freebody
• Amelia Elgar
• Debra Harrison
• Stephen McKenna
• Cath Moran
• Wendy Neilan
• Miriam Paul
• Catherine Pohlman
• Dave Hudson
• Luke Shoo
• and many others
For their various contributions:
– to many landholders for research access
– to several governments and non-government organisations for funding and other resources
– to my research collaborators:
Published scientific references
Byron Shire Council 2004. Byron Biodiversity Conservation Strategy. Byron Shire Council, Mullumbimby. Available at www.byron.nsw.gov.au/biodiversity
Catterall, C.P. 2016. Roles of non-native species in large-scale regeneration of moist tropical forests on anthropogenic grassland. Biotropica 48: 809–824.
Elgar, A.T., Freebody, K., Pohlman, C.L., Shoo, L.P., and Catterall, C.P. 2014. Overcoming barriers to seedling regeneration during forest restoration on tropical pasture land and the potential value of woody weeds. Frontiers in Plant Science 5:200. doi: 10.3389/fpls.2014.00200.
Kanowski, J., Catterall, C.P. and Neilan, W. 2008. The potential value of weedy regrowth for rainforest restoration: the case of Camphor Laurel in north-east New South Wales. Ecological Management and Restoration 9: 88-99.
Neilan W., Catterall C.P., Kanowski J. & McKenna, S. 2006. Do frugivorous birds assist rainforest succession in weed dominated oldfield regrowth of subtropical Australia? Biological Conservation 129: 393-407.
Paul, M., Catterall, C.P., Pollard, P.C, and Kanowski, J. 2010. Recovery of soil properties and functions in different rainforest restoration pathways. Forest Ecology and Management 259: 2083-2092.
Paul, M., Catterall, C.P., Kanowski, J. and Pollard, P.C. 2012 Recovery of rain forest soil seed banks under different reforestation pathways in eastern Australia. Ecological Management and Restoration 13: 144-152.
Shoo, L.P., Freebody, K., Kanowski, J. and Catterall, C.P. 2016. Slow recovery of tropical old field rainforest regrowth and the value and limitations of active restoration. Conservation Biology 30: 121–132.
3. Fact sheet “Woody weeds and habitat restoration: benefits and risks”
https://www.jaliigirr.com.au/wp-content/uploads/JBA-Woody-Weeds-
Factsheet.pdf
Further info
1. Lecture - Youtube
“Must we suppress aliens to restore nature?”
http://www.youtube.com/watch?v=TUawEB_fPx0
2. Paper Catterall, C.P. 2016. Roles of non-native species in large-scale
regeneration of moist tropical forests on anthropogenic
grassland. Biotropica 48: 809–824.