Are kangaroos and wallabies a problem for tree planting in Australia?

tree planting hillside victoria

by Janine Duffy

Ok, I have a confession. I love seeing a tree seedling half-eaten by a wallaby. But I don’t see it as often as I was led to expect.

A nibbled tree is sight that sends many tree planters into apoplexy. But for me, its not a problem, its a sign that wildlife lives, that I’ve planted the right tree in the right place and its healthy, and a beautiful native animal has had a good, safe meal. That’s assuming that it really was a wallaby that nibbled, and I’m not convinced of that.

The organisation I started, Koala Clancy Foundation, are a charity for wild animals, particularly koalas. We love all native wildlife including kangaroos and wallabies. Our plantings are for wild native animals, and we love it when wildlife eats the trees – that’s what they are planted for. Of course, it is ideal if a tree can reach a size that will survive regular browsing, and we don’t want to waste time or money planting trees that can’t make it.

I am always saddened to hear native wildlife demonised amongst tree planters. Surely there is a better approach.

I believe its up to us to learn from nature, to keep improving our systems to achieve a balance that benefits all wildlife.

So here’s a few ideas we are working on.

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Be like nature – plant a lot.

In nature, large trees like eucalyptus distribute hundreds of millions of seeds every season. A forest of River Red Gum can produce 250 million seeds per hectare, per year. Ants collect most of them (Ashton 1979), so only a very small percentage germinate, but that might still be 2,500,000 trees. Of those, in nature, only one might survive – and that’s how species ensure maximum fitness of their offspring, and feed wildlife at the same time.

eucalyptus camaldulensis importance to koalas
A magnificent, huge old River Red Gum on the Little River, VICTORIA

Direct seeding mimics nature, by distributing massive amounts of seed into a prepared bed. It works too. Most of the big revegetation groups use direct seeding to grow forests. There is no tree guard erected, and usually enough seedlings survive to achieve the desired result. It is so quick and cheap that even if poor conditions result in 100% failure, which is rare, it can be done again until it works. (and yes, it works in areas that have kangaroos – just have a look at the forest around Serendip Sanctuary, Victoria. All direct seeded during a drought, constantly inhabited by very hungry Eastern Grey Kangaroos).

Tubestock planting is hand-planting a seedling between 5 and 50cm high, and usually a tree guard is recommended. But why? Are the plants more vulnerable at that size? No. The simple answer is that tubestock is planted in smaller quantities, with a lot of effort and cost, and any failure is costly and depressing to the planter.

tubestock planting with tree guard
A normal setup for tubestock planting: seedling tree in forestry tube, corflute tree guard, two hardwood stakes.

Many tubestock plantings are just a few hundred plants, in a long line along a fence or river. Each plant is more vulnerable, simply because there are fewer to choose from.

But what if we could just plant more, plant better, plant more cheaply, and be more realistic about the survival of individual plants versus the creation of a forest? In fact, we must. Current revegetation efforts, though impressive, are still not approaching the quantity or quality of what is needed to protect biodiversity and help mitigate climate change. (Freudenberger 2018)

30000th tree planted for 2023
Plant more, plant better, plant more cheaply and be more realistic about outcomes.

Bottom up, not top down.

“Look after the pennies and the pounds will look after themselves”

18th century proverb

In conservation, it could be: Look after the wildflowers and groundcovers and the trees will look after themselves.

Or: Look after the insects and the koalas will look after themselves.

I think we go about revegetation the wrong way round. We pay too much attention to trees, and not enough to groundcovers, grasses and wildflowers. Yet a big gum tree is at the top of a pyramid: a big organism that lives for hundreds of years, and requires partnerships from millions of tiny short-lived organisms, from fungi in the soil, to pollinating insects in the air.

The same is true of a koala. It takes an entire forest ecosystem to support a koala. The microscopic soil life is as important to a koala as the leaves it eats – because the gum tree needs that soil life to produce leaves.

Generally we plant trees believing and hoping that they will create the small life and microclimate they need. But what if they can’t? What if we’ve destroyed the local seed bank, or polluted the soil?

I believe we can help re-establish soil health and small plant diversity while we are planting trees.

These days we plant sixes 1:5/big:small in a 1m spot-sprayed circle. For example – 1 eucalypt to 5 groundcovers. Depending on the site, it could be one River Red Gum Eucalyptus camaldulensis, surrounded by 2 Nodding Saltbush Einadia nutans, 1 Berry Saltbush Atriplex semibaccata, 1 Flax-liy Dianella longifolia and 1 Murnong Microseris walteri.

In addition we sprinkle native grass seed over the patch after planting. Our aim is to cover the soil with native life as fast as possible, thus protecting the soil, suppressing weeds, and encouraging insects. The growing tree is nurtured by this ‘living mulch’ approach.

innovative tree planting approach
Our spot setup, this one is a 2:4 big:small tree planting approach with one Hop Goodenia, one Silver Wattle and 4 groundcovers.

Some of the groundcovers are chosen because they will thrive long-term under a gum tree: the saltbushes and dianellas. The daisies probably won’t in the long-term, but by the time the tree grows enough to shade them out, they will have spread their seed far and wide.

As well, we inoculate the backfill soil with a cup of local soil dug from under a healthy bit of (preferably remnant) forest on the property. Planters are asked to backfill with this. This brings a bit of living soil microbiota to the baby plants.

Does it work? We’ve only been leaving small plants unguarded for two years, and planting in sixes this year. But early signs are good. The photo below shows one of many thriving unguarded groundcovers at a wetland site in the Barrabool Hills, Victoria. Atriplex semibaccata is also thriving and suppressing weeds. Calocephalus citreus and Pycnosurus globosus are also surviving. See more here: https://shorturl.at/FLg78

Milky Beauty-heads tree planting site
Unguarded Milky Beauty-heads thriving at a wet site after just two years.

Feeding wildlife is a beautiful thing.

I feel proud when I see a leaf of a tree I’ve planted chewed by a native animal.

That animal, let’s say its a Swamp Wallaby, needs that food. She doesn’t have a supermarket nearby, and she can’t call Uber Eats. We have left her very little to live off, and that little is declining in quality due to climate change.

A beautiful female Swamp Wallaby

When she eats my tree, which has been chosen as a critical component of the biodiversity of the region, she is getting the diet she is made for. She is recycling the nutrients from my tree into the soil, she might even help pollinate the plant, or she might carry the seeds to a new location. My tree needs her. Read how plants need animals here. (Catterall 2018)

That wallaby is not having to cover vast distances to fight off starvation. She’s not crossing as many roads, she’s not eating my neighbour’s beloved fruit tree. She has a better chance of raising a young that year.

Plants are very edible, as a rule. They are the only organisms on earth that can make food in their cells just from sunlight. Everything else must eat them, or eat those that eat them. So being the foundation of all life, they have developed strategies to cope or thrive under this pressure. Its not a one-way predator/victim relationship. Plants need animals and animals need plants. Read how ants have a relationship with eucalyptus seeds in the Jarrah forests of Western Australia.

A female Swamp Wallaby with her pouch joey in the You Yangs, Victoria

All we need to do is work with the natural systems, not against them.

It’s not my tree anyway. All I’ve done is place the seed in a suitable medium. All the magic has been created by nature – nature germinated the seed, provided the sun and water so it could grow, created the soil and micro-organisms in the potting mix. The Swamp Wallaby’s ancestors evolved with, and helped spread this tree’s ancestors.

It’s more the wallaby’s tree than it is mine.

To guard, or not to guard?

Plastic tree guards are a scourge. We do still use them, but only the one big plant in our six gets a guard. We do our best to collect and recycle them, and in 2024, we haven’t bought a single new tree guard – all our guards are on their second or third use. Watch: https://www.facebook.com/reel/794329385515935

I don’t like that they are plastic, I don’t like that they need stakes, and I don’t like the time it takes to erect them. You can plant quicker without them, with lower emissions.

This article is from the UK, but it makes an interesting argument:
https://www.theguardian.com/environment/2021/aug/24/trees-should-be-planted-without-plastic-guards-says-uk-study-aoe

Already, lots of revegetation projects in Australia are tree guard-free. You won’t read about it much, but I understand that most of the very big projects are direct seeded, and in some regions in Australia browsing wildlife numbers are low, plant growth rates are high and tree guards are just not necessary.

Depending on your project, you may still need tree guards. We do, but I am searching for alternatives.

I am very aware of the following:

  • Can you remove and reuse, recycle or dispose of them all? (And if not, would you throw that much plastic into your river and feel good about it?) We are trying, and its a lot of work and just as expensive as buying new ones.
  • Are the stakes sustainable? Or have native trees been cut down somewhere so that you can plant trees? We now buy only pointed bamboo stakes, and only use hardwood stakes that are recycled from earlier projects.
  • Is the cost worth it? Or could you plant more with that money – either by planting groundcovers in addition to trees, or by increasing the planted area?

I think we are being too possessive, and thinking short-term about the trees we plant. If the forest is created, what does it matter if a few individual trees are not long-lived?

two year old trees Barwon River
Two year old trees on the Barwon River, Victoria

Know your wildlife.

It’s really important to know our wildlife species if we are to work with them positively. Local knowledge usually doesn’t help – there is widespread confusion about what is a wallaby and what is a kangaroo.

I’ve spent my entire working life as a Wildlife Guide for Echidna Walkabout Nature Tours, finding, identifying and watching macropods. I am fascinated by them. I wrote this: https://echidnawalkabout.wordpress.com/2018/06/21/macropods-of-australia-checklist/ and I’m still astonished that few similar articles exist. Australia’s interest in the kangaroo family is low.

Kangaroos are the largest macropods in Australia, and the largest marsupials on earth. There are 6 species of kangaroo in Australia: the Eastern Grey, Western Grey, Red, Antilopine and the Common Wallaroo/Euro and Black Wallaroo.

Wallabies have far more species: 32 species in several distinct groups. There are rock-wallabies (17 species), nailtail wallabies (2sp), pademelons (3sp), hare-wallabies (2sp) and others all considered wallabies.

See comparison photos and the distributions of the big kangaroos and wallabies here: https://echidnawalkabout.com.au/macropods-kangaroos-of-australia/

In southern Victoria we have only Eastern Grey Kangaroos, Swamp Wallabies and in a few places Red-necked Wallabies.

Eastern Grey Kangaroos are mob (herd) animals that are rarely seen alone. The largest males and females stand up to 1.5m tall, and are clearly larger than ‘wallabies’. But most in the mob are smaller than that – they grow to full height over many years, and the majority of the mob are intermediate-sized young animals. They have a fairly even grey colour all over, lighter on the belly and legs, with no strong contrast and no bright spots of colour.

koalas in the wild tour
Eastern Grey Kangaroos: in a mob, many different sizes, grey all over

Eastern Grey Kangaroos are grazers. They really only eat grass. They will only eat shrubs when they are starving, but they are not made for browsing. They will push over a tree guard or a young tree, box with it and play with it. It’s possible that they will remove a tree planted in a spot that they prefer for lying in the sun, but that’s about it. As a rule, Eastern Grey Kangaroos are not a problem for tree planting projects.

Swamp Wallabies are loners that are rarely seen together. ‘Lots of wallabies’ is not really a thing in southern Victoria – a large property might be home to 5 individuals. The largest male stands to 1m tall. They are nearly black or dark grey on the head and back, with a rufous orange belly and around and inside the ears. They often have a white beard along their jawline. They have black paws and tail.

Swamp Wallabies are generalist browsers – they eat the leaves of shrubs and trees, plus grass and fungi. They don’t visit the same patch every night, instead circulating through their large (16ha) home range. Some individual plants will be heavily browsed, others of the same species and provenance will be barely touched. Swamp Wallabies are not numerous in the farming districts we work in, and though they can eat revegetation plants, I don’t believe they are a problem for tree planting projects.

Swamp Wallaby: alone, black, grey and ginger with white jaw and black paws.

What you see, or hear about, isn’t necessarily the culprit.

I have yet to find a scientific publication that details the animals that eat seedlings in revegetation sites in Australia by proportion of plants eaten, or damage done, or even an article that splits native herbivores from feral ones. It seems that widespread deleterious browsing by native herbivores is an idea that is widely accepted but somewhat unsupported. If you know of any, please send them through to me.

In my experience, I have seen revegetation projects thriving and others struggling. I haven’t done the monitoring required to be sure of the culprits, and I don’t know anyone who has done that monitoring either.

Big, day-active animals are more noticeable than small, nocturnal ones. Herd animals are more noticeable than loners. It is very common for kangaroos to be blamed for everything, because people see them.

There is also a widespread prejudicial attitude towards wild, un-owned animals compared to owned animals. Wild animals are not considered anyone’s valuable property. (And, no-one* gets offended if you blame kangaroos or wallabies. *well, actually I do – I love macropods and I feel hurt when they are disparaged)

Many myths exist about our native animals, particularly about kangaroos. There are few reliable sources of information, and little unbiased research. We constantly hear that they are overabundant, but this can’t possibly be true when we’ve destroyed 99% of the natural temperate grasslands Eastern Grey Kangaroos prefer. Yes, sadly we have removed their natural predators from most areas, but our roads have more than picked up the slack, killing an estimated 9 million kangaroos and wallabies every year. (Burgin 2008). We are still the world capital of mammal extinctions, and many wallabies and small macropods have disappeared from our land. Kangaroos and their relatives are very sensitive to climate change (Ritchie 2008, Juillard 2022), and their numbers are heavily impacted by drought. Their populations can only increase at 10% per year, yet 10% are killed on the roads, and many others are shot.

Kangaroos and wallabies also suffer from a shifting baseline: Each generation of people gets used to a different norm. So a landowner today who sees 5 kangaroos in a normal evening, thinks that 10 is a lot. A landowner 50 years ago saw 20 kangaroos in a normal evening, so 40 was a lot.

Lastly, there is an attitude that feral animals like rats and rabbits are a sign of poor management, so they are rarely talked about or admitted to. I have found very few articles about the impact of rabbits on revegetation (especially compared to the number of articles on the impact of wallabies & kangaroos), yet it is known that they have a serious impact. Less than one rabbit per hectare is enough to stop natural regeneration of native trees and shrubs.

In Australia, most of us are taught little about our native wildlife. Most of us could name and identify more breeds of cattle than species of kangaroo and wallaby.

Are we really able to be objective in the face of so many myths, so little research and so much prejudice?
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The problem of livestock for tree planting.

Livestock getting into revegetation plots is a very common problem that is rarely admitted by anyone. I imagine it is embarrassing – it means fences are not properly maintained (though it is nearly impossible to keep fences perfect at all times), and all those expensive, and lovingly-planted trees are going down the throats of someone’s sheep or cattle.

Don’t underestimate the damage livestock can do. There’s a reason why fencing is essential to separate reveg from livestock – plastic, mesh or wire tree guards of any size are not sufficient to protect a tree against sheep or cattle. They reach in, pull the tree out by the roots, or just push the guard over. Until trees are about 5metres high, they will be destroyed by livestock. Even after that, livestock still do damage by rubbing, eating the bark, compacting the soil, eating all the seedlings preventing future recruitment.

Even with secure fencing, sheep, cattle, goats, and to a lesser degree, horses, have the ability and initiative to get through most fences at some time. The protected area is full of delicious variety and excitement, and they push at fences to get to the tasty treats. Eventually they find or make a hole, and follow each other in and out as they choose. Fixing fences is a land manager’s constant headache, and we understand and accept that.

I’ve lost count of the times I’ve had to shoo livestock out of our revegetation plots while visiting to check tree progress or collect tree guards.

So it comes as a double disappointment to find trees you’ve lovingly planted, dead beside the guard because of a curious sheep, then to have the landowner blame the wallabies or kangaroos.

If we can simply admit that livestock always gets in, and that some of the damage to newly-planted trees is from sheep/cattle, some from rabbits, some from wallabies, some from insects, some from poor planting, and some from weather we will go some way towards more productive revegetation.

If we can live with the damage from our domestic and feral animals, we can live with it from our precious native animals too.
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Take your location, site and circumstances into account.

Most information about native wildlife, browsing and tree planting is very general. Every site is different, and most of what you read or hear will not apply. There is no one-size-fits-all.

Everything I have written applies to my projects, in the wider Geelong area, southern Victoria. It may or may not be useful to you. But I hope it provides some food for thought.

Case study 1: Staughton Vale, Victoria

My property in Staughton Vale, Victoria is 18 hectares on the slope of the Brisbane Ranges escarpment, a derived grassland as a result of past clearing for farming. Native grasses cover most of the flattest 2ha , and dry open woodland of Yellow Gum, Red Box and Messmate covers the rest. We have no stock, no dogs and few rabbits. We have a small population of resident Eastern Grey Kangaroos who seem to spend most days resting in the woodland, and are often seen at dusk and dawn. Their numbers hardly change at all from year to year. They visit the neighbouring properties, and exhibit no fixed pattern in their grazing – the spots they prefer change all the time.

From time to time we also see a Swamp Wallaby. They are territorial, shy and have large home ranges, so I suspect he is always nearby, just not always seen.

I have planted many species of plants with and without guards, and most are left untouched by the kangaroos, and only eaten rarely by the Swamp Wallaby. We now have large Grey Box, Yellow Box, River Red Gum, Manna Gum, Black Sheoak, Wirilda, Lightwood, Bacchus Marsh Wattle, Silver and Black Wattle trees as a result. *(bold) trees planted in guards for first two years.

More recently I’ve been planting shrubs and groundcovers. We now have large healthy Hop Goodenia, River Bottlebrush, Prickly Moses, Woolly Tea-tree, Fragrant Saltbush, Pomaderris, Mat-rush, Sticky Boobialla, Rock Correa, Golden Grevillea and Gold-dust Wattle. Most were also planted in tree guards for the first two years.

The following plants were planted with no guards at all and are growing well: Lemon and Milky Beauty-heads Calocephalus citreus & C lacteus, Common and Clustered Everlastings Chrysocephalum apiculatum and C semipapposum, Copper-wire Daisies Podolepis jaceoides & P. linearifolia, Xerochrysum viscosum, Rock Correa Correa glabra, Creeping Boobialla Myoporum parvifolium, Rosemary Grevillea Grevillea rosmarinfolia, Silver Tussock Poa labilladiere and lots of saltbushes including Einadia nutans, hastata, Atriplex semibaccata and Rhagodia parabolica.

In conclusion, I think our future is tree guard-free, bigger projects, and more realistic attitudes to individual tree survival versus landscape change.

I think native wildlife is overly implicated in damage to revegetation. I’m not saying they don’t do damage, but I think their impact is being over-estimated in some places. Conversely, non-native animals – both domestic livestock and feral pest species – are not being managed for their part in damage to tree planting projects. This is a subject that needs more research and discussion.

before tree planting
Tree planting on a site with a couple of resident Swamp Wallabies and a small mob of Eastern Grey Kangaroos
tree planting progress 2 years later
Good growth of all plants on the site 2 years later.

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NOTES & REFERENCES:

Andres, S.E., Atkinson, J., Coleman, D., Brazill‐Boast, J., Wright, I.J., Allen, S. and Gallagher, R.V., 2023. Constraints of commercially available seed diversity in restoration: Implications for plant functional diversity. Plants, People, Planet. https://doi.org/10.1002/ppp3.10523

Ashton, D.H., 1979. Seed harvesting by ants in forests of Eucalyptus regnans F. Muell. in central Victoria. Australian Journal of Ecology, 4(3), pp.265-277. https://www.antwiki.org/wiki/images/f/fe/Ashton%2C_D.H._1979._Seed_harvesting_by_ants_in_forests_of_Eucalyptus_regnans.pdf

Burgin, S. and Brainwood, M., 2008. Comparison of road kills in peri-urban and regional areas of New South Wales (Australia) and factors influencing deaths. Too close for comfort: Contentious issues in human-wildlife encounters, pp.137-144. https://www.researchgate.net/profile/David-Newsome-4/publication/46156167_To_feed_or_not_to_feed_A_contentious_issue_in_wildlife_tourism/links/00463532a741c9cf4c000000/To-feed-or-not-to-feed-A-contentious-issue-in-wildlife-tourism.pdf?_sg%5B0%5D=started_experiment_milestone&origin=journalDetail#page=151

Catterall, C.P., 2018. Fauna as passengers and drivers in vegetation restoration: a synthesis of processes and evidence. Ecological Management & Restoration, 19, pp.54-62. https://doi.org/10.1111/emr.12306

Freudenberger, D., 2018. Matching effort to threat: Strategies to increase the scale and effectiveness of revegetation in southern Australia. Ecological Management & Restoration, 19, pp.6-10. https://doi.org/10.1111/emr.12322

Juillard, L.Q. and Ramp, D., 2022. The Impacts of drought on the health and demography of Eastern grey kangaroos. Animals, 12(3), p.256. https://doi.org/10.3390/ani12030256

Ritchie, E.G. and Bolitho, E.E., 2008. Australia’s savanna herbivores: bioclimatic distributions and an assessment of the potential impact of regional climate change. Physiological and Biochemical Zoology, 81(6), pp.880-890.
https://www.sciencedaily.com/releases/2008/10/081015120734.htm

Wanless, T.L., 2003. Seed Dispersal by Ants in Jarrah Forest Restorations of Western Australia.
https://conservancy.umn.edu/server/api/core/bitstreams/7c95d70c-fa13-4cf6-b81d-a771d1aaf1b3/content

Direct seeding fact sheets:

https://cdn.environment.sa.gov.au/landscape/docs/ny/sustainable-agriculture-direct-seeding-fact.pdf

https://www.greeningaustralia.org.au/wp-content/uploads/2017/11/FACT-SHEET_Direct-Seeding-Overview.pdf

Lack of small plant diversity: https://theconversation.com/only-10-of-native-plants-can-be-bought-as-seed-a-big-problem-for-nature-repair-heres-how-we-can-make-plantings-more-diverse-228899#

Are kangaroos at risk: https://theconversation.com/factcheck-are-kangaroos-at-risk-37757

Rabbit damage to revegetation:

https://www.swifft.net.au/resources/31_rabbit%20control%20in%20wildlife%20habitat.pdf

http://gwlap.org.au/rabbit-control/

https://pestsmart.org.au/toolkit-resource/economic-and-environmental-impacts-of-rabbits-in-australia/

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