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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

. o

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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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

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wit

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ea

ve

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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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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.